text:
\section{Introduction}

Titan has a dense atmosphere, composed of $\mathrm{N_2}$ and $\mathrm{CH_4}$, and many trace gases such as  hydrocarbons (e.g. $\mathrm{C_2H_6}$, $\mathrm{C_2H_2}$) and nitriles (e.g. $\mathrm{HCN}$, $\mathrm{HC_3N}$) produced by its rich photochemistry.  Like Earth, Titan has a  stratosphere, located between 50~km ($\sim 100$~mbar) and 400~km  ($\sim 0.01$~mbar), characterized by the increase of its temperature with altitude because of the absorption of incoming sunlight by methane and hazes. Titan's atmosphere undergoes strong variations of insolation, due to its obliquity ($26.7^{\circ}$) and to the eccentricity of Saturn's orbit around the Sun (0.0565). \\

The Cassini spacecraft monitored Titan's atmosphere during 13 years (from 2004 to 2017), from northern winter to summer solstice. Its data are a unique opportunity to study the seasonal evolution of its stratosphere, especially with mid-IR observations from Cassini/CIRS (Composite InfraRed Spectrometer, \citet{Flasar2004}). They showed that at pressures lower than 5~mbar, the stratosphere exhibits strong seasonal variations of temperature and composition related to changes in atmospheric dynamics and radiative processes. For instance, during northern winter (2004-2008), high northern latitudes were enriched in photochemical products such as HCN or $\mathrm{C_4H_2}$, while there was a "hot spot" in the upper stratosphere and mesosphere (0.1 - 0.001~mbar, \citet{Achterberg2008, Coustenis2007, Teanby2007b,Vinatier2007}). These observations were interpreted as evidence of subsidence above the North pole during winter, which is a part of the pole-to-pole atmospheric circulation cell predicted for solstices by Titan GCMs (Global Climate Models, \citet{Lora2015,Lebonnois2012a,Newman2011}). These models also predict that the circulation pattern should reverse  around equinoxes, via a transitional state with two equator-to-pole cells. These changes began to affect the South pole in 2010, when measurements showed that pressures inferior to 0.03~mbar exhibited an enrichment in gases such as HCN or $\mathrm{C_2H_2}$, which propagated downward during autumn, consistent with the apparition of a new circulation cell with subsidence above the South pole \citep{Teanby2017,Vinatier2015}.\\

 Some uncertainties remain about the seasonal evolution of the lower part of the stratosphere, i.e. at pressures from 5~mbar (120~km) to 100~mbar (tropopause, 50~km). Different estimates of radiative timescales have been calculated for this region. In \citet{Strobel2010}, the radiative timescales in this region vary from 0.2 Titan years at 5~mbar to 2.5 Titan years at 100~mbar. This means that the lower stratosphere should be the transition zone from parts of the atmosphere which are sensitive to  seasonal insolation variations, to parts of the atmosphere which are not.  In contrast, in the radiative-dynamical model of \citet{Bezard2018}, radiative timescales are between 0.02 Titan year at 5~mbar and 0.26 Titan year at 100~mbar, implying that this whole region should exhibit a response to the seasonal cycle.\\

From northern winter to equinox, CIRS mid-IR observations showed that temperature variations were lower than 5~K between 5~mbar and 10~mbar \citep{Bampasidis2012,Achterberg2011}.  Temporal variations intensified after spring equinox, as \citet{Coustenis2016} measured a cooling by 16~K and an increase in gases abundances at $70^{\circ}$S from 2010 to 2014, at 10~mbar, associated with the autumn subsidence above the South pole. \citet{Sylvestre2018} showed that this subsidence affects pressure levels as low as 15~mbar as they measured  strong enrichments in $\mathrm{C_2N_2}$, $\mathrm{C_3H_4}$, and $\mathrm{C_4H_2}$~at high southern latitudes from 2012 to 2016 with  CIRS far-IR observations. However, we have little information on temperatures and their seasonal evolution for pressures greater than 10~mbar. Temperatures from the surface to 0.1~mbar can be measured by Cassini radio-occultations, but the published profiles were measured mainly in 2006 and 2007 \citep{SchinderFlasarMaroufEtAl2011,Schinder2012}, so they provide little information on seasonal variations of temperature. \\

In this study, we analyse all the available far-IR Cassini/CIRS observations to probe temperatures from 6~mbar to 25~mbar, and measure the seasonal  variations of  lower stratospheric temperatures. As these data were acquired throughout the Cassini mission from 2004 to 2017, and cover the whole latitude range, they provide a unique overview of the thermal evolution of the lower stratosphere from northern winter to summer solstice, and a better understanding of the radiative and dynamical processes at play in this part of Titan's atmosphere.\\

\section{Data analysis}

	\subsection{Observations}
	 We measure lower stratospheric temperatures using Cassini/CIRS \citep{Flasar2004} spectra. CIRS is a thermal infrared spectrometer with three focal planes operating in three different spectral domains: 10 - 600$~\mathrm{cm^{-1}}$ (17 - 1000$~\mathrm{\mu m}$) for FP1,  600 - 1100$~\mathrm{cm^{-1}}$ (9 - 17 $~\mathrm{\mu m}$) for FP3, and 1100 - 1400$~\mathrm{cm^{-1}}$ (7 - 9$~\mathrm{\mu m}$) for FP4. FP1 has a single circular detector with an angular field of view of 3.9~mrad, which has an approximately Gaussian spatial response with a FWHM of 2.5 mrad. FP3 and FP4 are each composed of a linear array of ten detectors. Each of these detectors has an angular field of view of 0.273~mrad. \\

	 In this study,  we use FP1 far-IR observations, where nadir spectra are measured at a resolution of 0.5$~\mathrm{cm^{-1}}$,  in  "sit-and-stare" geometry (i.e the FP1 detector probes the same latitude and longitude during the whole duration of the acquisition). In this type of observation, the average spatial field of view is 20$^\circ$ in latitude. An acquisition lasts between 1h30 and 4h30, allowing the recording of 100 to 330 spectra. The spectra from the same acquisition are averaged together, which increases the S/N by a factor $\sqrt{N}$ (where N is the number of spectra).  As a result, we obtain an average spectrum where the rotational lines  of $\mathrm{CH_4}$~(between 70$~\mathrm{cm^{-1}}$ and 170$~\mathrm{cm^{-1}}$) are resolved and can be used to retrieve Titan's lower stratospheric temperature. An example averaged spectrum is shown in Fig. \ref{fig_spec}.\\

	 We analysed all the available observations with the characteristics mentioned above. As shown in table \ref{table_obs}, this type of nadir far-IR observation has been performed throughout the Cassini mission (from 2004 to 2017), at all latitudes.  Hence, the analysis of this dataset enables us to get an overview of Titan's lower stratosphere and its seasonal evolution.\\

	\begin{figure}[!h]
	\includegraphics[width=1\columnwidth]{Spectra_89N_0703}
	\caption{Example of average spectrum measured with the FP1 detector of Cassini/CIRS (in black) and its fit by NEMESIS (in red). The measured spectrum was obtained after averaging 106 spectra observed at $89^{\circ}$N in March 2007. The rotational lines of $\mathrm{CH_4}$~are used to retrieve stratospheric temperature. The "haystack" feature is visible only at high latitudes during autumn and winter. }
	\label{fig_spec}
\end{figure}

	\subsection{Retrieval method}
		 We follow the same method as \citet{Sylvestre2018}. We use the portion of the spectrum between  70~$\mathrm{cm^{-1}}$ and 400~$\mathrm{cm^{-1}}$, where the main spectral features are: the ten rotational lines of $\mathrm{CH_4}$~(between 70$~\mathrm{cm^{-1}}$ and 170$~\mathrm{cm^{-1}}$), the $\mathrm{C_4H_2}$~band at $220~\mathrm{cm^{-1}}$,  the $\mathrm{C_2N_2}$~band at  $234~\mathrm{cm^{-1}}$, and the $\mathrm{C_3H_4}$~band at  $327~\mathrm{cm^{-1}}$ (see Fig. \ref{fig_spec}). The continuum emission comes from the collisions between the three main components of Titan's atmosphere (N$_2$, $\mathrm{CH_4}$, and H$_2$), and from the spectral contributions of the hazes. \\

		We retrieve the temperature profile using the constrained non-linear inversion code NEMESIS \citep{Irwin2008}. We define a reference atmosphere, which takes into account the abundances of the main constituents of Titan's atmosphere measured by Cassini/CIRS \citep{Coustenis2016,Nixon2012,Cottini2012,Teanby2009}, Cassini/VIMS \citep{Maltagliati2015}, ALMA \citep{Molter2016} and Huygens/GCMS\citep{Niemann2010}. We also consider the haze distribution and properties measured in previous studies with Cassini/CIRS \citep{deKok2007,deKok2010b,Vinatier2012}, and Huygens/GCMS \citep{Tomasko2008b}. We consider four types of hazes, following \citet{deKok2007}:  hazes 0 ($70~\mathrm{cm^{-1}}$ to $400~\mathrm{cm^{-1}}$), A (centred at $140~\mathrm{cm^{-1}}$), B (centred at $220~\mathrm{cm^{-1}}$) and C (centred at  $190~\mathrm{cm^{-1}}$).  For the spectra measured at high northern and southern latitudes during autumn and winter, we add an offset from 1 to $3~\mathrm{cm^{-1}}$  to the nominal haze B cross-sections between 190~$\mathrm{cm^{-1}}$ and 240~$\mathrm{cm^{-1}}$, as in \citet{Sylvestre2018}.  This modification improves the fit of the continuum in the "haystack" which is a strong emission feature between 190~$\mathrm{cm^{-1}}$ and 240~$\mathrm{cm^{-1}}$ (see Fig. \ref{fig_spec}) seen at high latitudes during autumn and winter (e.g. in  \citet{Coustenis1999, deKok2007, Anderson2012, Jennings2012, Jennings2015}). The variation of the offset allows us to take into account the evolution of the shape of this feature throughout autumn and winter. The composition of our reference atmosphere and the spectroscopic parameters adopted for its constituents are fully detailed in \citet{Sylvestre2018}.\\

		We retrieve the temperature profile and scale factors applied to the \textit{a priori} profiles of $\mathrm{C_2N_2}$, $\mathrm{C_4H_2}$, $\mathrm{C_3H_4}$, and hazes 0, A, B and C, from the spectra using the constrained non-linear inversion code NEMESIS \citep{Irwin2008}. This code generates synthetic spectra from the reference atmosphere. At each iteration, the difference between the synthetic and the measured spectra is used to modify the profile of the retrieved variables, and minimise a cost function, in order to find the best fit for the measured spectrum. \\

		The sensitivity of the spectra to the temperature can be measured with the inversion kernels for the temperature (defined as $K_{ij}~=~\frac{\partial I_i}{\partial T_j}$, where $I_i$ is the radiance measured at wavenumber $w_i$, and $T_j$ the temperature at pressure level $p_j$) for several wavenumbers. The contribution of the methane lines to the temperature measurement can be isolated by defining their own inversion kernels $K^{CH_4}_{ij}$ as follows:
	\begin{equation}
		K^{CH_4}_{ij} = K_{ij} - K^{cont}_{ij}
	\end{equation}
	\noindent where $K^{cont}_{ij}$ is the inversion kernel of the continuum for the same wavenumber. Figure \ref{fig_cf} shows $K^{CH_4}_{ij}$ for three of the rotational methane lines in the left panel, and the comparison between the sum of the 10 $K^{CH_4}_{ij}$ (for the 10 rotational $\mathrm{CH_4}$~lines) and inversion kernels for the continuum ($K^{cont}_{ij}$ at the wavenumbers of the $\mathrm{CH_4}$~lines and $K_{ij}$ outside of the $\mathrm{CH_4}$~lines) in the right panel. The $\mathrm{CH_4}$~lines allow us to measure lower stratospheric temperatures generally between 6~mbar and 25~mbar, with a maximal sensitivity at 15~mbar. The continuum emission mainly probes temperatures at higher pressures, around the tropopause and in the troposphere.  The continuum emission mostly originates from the $\mathrm{N_2}$-$\mathrm{N_2}$ and $\mathrm{N_2}$-$\mathrm{CH_4}$~collisions induced absorption with some contribution from the hazes, for which we have limited constraints.  However, Fig. \ref{fig_cf} shows that the continuum emission comes from pressure levels located several scale heights below the region probed by the $\mathrm{CH_4}$~lines, so the lack of constraints on the hazes and tropospheric temperatures does not affect the lower stratospheric temperatures which are the main focus of this study.\\

	    \begin{figure}[!h]
		\includegraphics[width=1\columnwidth]{CF_72N_0704_v2}
		\caption{Sensitivity of temperature measurements at $72^{\circ}N$ in April 2007. \textit{Left panel}: Normalised inversion kernels $K^{CH_4}_{ij}$ in three of the $\mathrm{CH_4}$~rotational lines. \textit{Right panel:} Comparison between the inversion kernels in the continuum ($K^{cont}_{ij}$ for three of the $\mathrm{CH_4}$~lines in dot-dashed lines, and $K_{ij}$ for other wavenumbers in the continuum in dashed lines) and the sum of the inversion kernels $K^{CH_4}_{ij}$ of the $\mathrm{CH_4}$~rotational lines.   $\mathrm{CH_4}$~rotational lines dominate the temperature retrievals in the lower stratosphere, generally from 6 to 25~mbar  (and up to 35~mbar,  depending on the datasets). The continuum emission probes temperatures at pressures higher than 50~mbar, mainly in the troposphere.}
		\label{fig_cf}
	    \end{figure}

	\subsection{Error sources}
		The main error sources in our temperature retrievals are the measurement noise and the uncertainties related to the retrieval process such as forward modelling errors or the smoothing of the temperature profile. The total error on the temperature retrieval is estimated by NEMESIS and is in the order of 2~K from 6~mbar to 25~mbar.\\

       The other possible error source is the uncertainty on $\mathrm{CH_4}$~abundance, as \citet{Lellouch2014} showed that it can vary from 1\% to 1.5\% at 15 mbar. We performed additional temperature retrievals on several datasets, in order to assess the effects of these variations on the temperature retrievals. First, we selected datasets for which $\mathrm{CH_4}$~abundance was measured by \citet{Lellouch2014}. In Figure \ref{fig_TCH4}, we show examples of these tests for two of these datasets: $52^{\circ}$N in May 2007 and $15^{\circ}$S in October 2006, for which \citet{Lellouch2014} measured respective $\mathrm{CH_4}$~abundances of $q_{CH_4} = 1.20 \pm 0.15\%$ and $q_{CH_4} = 0.95 \pm 0.08 \%$ (the nominal value for our retrievals is $q_{CH_4} = 1.48 \pm 0.09\%$ from \citet{Niemann2010}). At $52^{\circ}$N, the temperature profile obtained with the methane abundance from \citet{Lellouch2014} does not differ by more than 4~K from the nominal temperature profile. At 15 mbar (where the sensitivity to temperature is maximal in our retrievals), the difference of temperature between these two profiles is 2~K. Even a $\mathrm{CH_4}$~volume mixing ratio as low as 1\% yields a temperature only 4~K warmer than the nominal temperature at 15~mbar. At $15^{\circ}$S, the difference of temperature between the nominal retrieval and the retrieval with the methane abundance retrieved by \citet{Lellouch2014} ($q_{CH_4}=0.95\%$), is approximately 9~K on the whole pressure range.\\

       We performed additional temperature retrievals using CIRS FP4 nadir spectra measured at the same times and latitudes as the two datasets shown in Figure \ref{fig_TCH4}. In FP4 nadir spectra, the methane band $\nu_4$ is visible between $1200~\mathrm{cm^{-1}}$ and $1360~\mathrm{cm^{-1}}$. This spectral feature allows us to probe temperature between 0.1~mbar and 10~mbar, whereas methane rotational lines in the CIRS FP1 nadir spectra generally probe temperature between 6~mbar and 25~mbar. Temperature can thus be measured with both types of retrievals from 6~mbar to 10~mbar.  We performed FP4 temperature retrievals with the nominal methane abundance and the abundances measured by \citet{Lellouch2014}, as shown in Figure \ref{fig_TCH4}. FP4 temperature retrievals seem less sensitive to changes in the methane volume mixing ratio, as they yield a maximal temperature difference of 3~K at $52^{\circ}$N , and 4~K at $15^{\circ}$S between 6~mbar and 10~mbar. In both cases, FP1 and FP4 temperature retrievals are in better agreement in their common pressure range when the nominal methane abundance ($q_{CH_4}=1.48\%$) is used for both retrievals. This suggests that $q_{CH_4}=1.48\%$ is the best choice, at least in the pressure range covered by both types of temperature retrievals (from 6~mbar to 10 mbar). Changing the abundance of $\mathrm{CH_4}$~in the whole stratosphere seems to induce an error on the temperature measurements between 6~mbar and 10 mbar (up to 9~K at $15^{\circ}$S), which probably affects the temperature at 15~mbar in the FP1 retrievals, because of the vertical resolution of nadir retrievals (represented by the width of the inversion kernels in Fig. \ref{fig_cf}).  Consequently, assessing the effects of $\mathrm{CH_4}$~abundance variations on temperature at 15~mbar by changing $q_{CH_4}$ in the whole stratosphere seems to be a very unfavourable test, and the uncertainties on temperature determined by this method are probably overestimated for the FP1 temperature retrievals. Overall, when retrieving temperature from CIRS FP1 nadir spectra with $q_{CH_4}=1\%$ for datasets spanning different times and latitudes, we found temperatures warmer than our nominal temperatures by 2~K to 10~K at 15~mbar, with an average of 5~K. In \cite{Lellouch2014}, authors found that temperature changes by 4-5 K on the whole pressure range when varying $q_{CH_4}$ at $15^{\circ}$S, but they determined temperatures using FP4 nadir and limb data, which do not probe the 15 mbar pressure level.\\

        \begin{figure}
            \centering
            \includegraphics[width=1\columnwidth]{Temperature_profiles_52N_0705}\\
            \includegraphics[width=1\columnwidth]{Temperature_profiles_15S_0610}\\
            \caption{Temperature profiles from CIRS FP1 and FP4 nadir observations at $52^{\circ}$N in May 2007 (top panel) and $15^{\circ}$S in October 2006 (bottom panel), retrieved with the methane abundances measured by \citet{Niemann2010} (nominal value in this study) and \citet{Lellouch2014}. In both cases, the nominal value  from \citet{Niemann2010} yields a better agreement between the two types of observations.}
            \label{fig_TCH4}
        \end{figure}

\section{Results}
\label{sect_res}
	\begin{figure}[!hp]
		\includegraphics[width=1\columnwidth]{carte_2d_6mbar_v2}\\
		\includegraphics[width=1\columnwidth]{carte_2d_15mbar_v2}
		\caption{Evolution of temperatures at 6~mbar (120~km) and 15~mbar (85~km) from northern winter (2004) to summer (2017). The length of the markers shows the average size of the field of view of the CIRS FP1 detector. Temperatures exhibit similar strong seasonal changes at both pressure levels, especially at the poles.}
		\label{fig_ev_saiso}
	\end{figure}

	\begin{figure}[!h]
		\includegraphics[width=1\columnwidth]{var_saiso_GCM}

		\caption{Meridional distribution of temperatures at 6~mbar (120~km) and 15~mbar (85~km), for three different seasons: late northern winter (2007, blue triangles), mid-spring (2013, green circles), and near summer solstice (from July 2016 to September 2017, red diamonds). The plain lines are the meridional distributions given by GCM simulations at comparable seasons (see section \ref{sect_discu}). In both observations and model the meridional gradient of temperatures evolves from one season to another at both pressure levels.}
		\label{fig_var_saiso}
	\end{figure}
			Figures \ref{fig_ev_saiso} and \ref{fig_var_saiso} show the temperatures measured with Cassini/CIRS far-IR nadir data at 6~mbar (minimal pressure probed by the CIRS far-IR nadir observations) and 15~mbar (pressure level where these observations are the most sensitive). Figure \ref{fig_ev_saiso} maps the seasonal evolution of temperatures throughout the Cassini mission (from 2004 to 2017, i.e. from mid-northern winter to early summer), while Figure \ref{fig_var_saiso} is focused on the evolution of the meridional gradient of temperature from one season to another. In both figures, both pressure levels exhibit significant seasonal variations of temperature and follow similar trends. Maximal temperatures are reached near the equator in 2005 (152~K at 6~mbar, 130~K at 15~mbar, at $18^{\circ}$S, at $L_S=300^{\circ}$), while the minimal temperatures are reached at high southern latitudes in autumn (123~K at 6~mbar, 106~K at 15~mbar at $70^{\circ}$S in 2016, at $L_S=79^{\circ}$).\\

			The maximal seasonal variations of temperature are located at the poles for both pressure levels. At high northern latitudes ($60^\circ$N - $90^\circ$N), at 15~mbar, the temperature increased overall from winter to summer solstice. For instance at $70^{\circ}$N, temperature increased by 10~K from January 2007 to September 2017.  At 6~mbar, temperatures at  $60^{\circ}$N stayed approximately constant from winter to spring, whereas latitudes poleward from $70^{\circ}$N warmed up.  At $85^{\circ}$N, the temperature increased continuously from 125~K in March 2007 to 142~K in September 2017.\\

			In the meantime, at high southern latitudes ($60^\circ$S - $90^\circ$S), at 6~mbar and 15~mbar, temperatures strongly decreased from southern summer (2007) to late autumn (2016). It is the largest seasonal temperature change we measured in the lower stratosphere. At $70^{\circ}$S, temperature decreased by 24~K at 6~mbar and by 19~K at 15~mbar between January 2007 and June 2016. This decrease seems to be followed by a temperature increase toward winter solstice. At $70^{\circ}$S, temperatures varied by $+8$~K at 6~mbar from June 2016 to April 2017. Temperatures at high southern latitudes began to evolve in November 2010 at 6~mbar, and 2 years later (in August 2012) at 15~mbar.\\

			Other latitudes experience moderate seasonal temperature variations. At low latitudes (between $30^{\circ}$N and $30^{\circ}$S), temperature decreased overall from 2004 to 2017 at both pressure levels. For instance, at the equator, at 6~mbar temperature decreased by 6~K from 2006 to 2016.  At mid-southern latitudes, temperatures stayed constant from summer (2005) to mid-autumn (June 2012 at 6~mbar,  and May 2013 at 15~mbar), then they decreased by approximately 10~K from 2012-2013 to 2016. At mid-northern latitudes temperatures increased overall from winter to spring. At $50^{\circ}$N, temperature increased from 139~K to 144~K from 2005 to 2014.  In Figure \ref{fig_var_saiso}, at 6~mbar and 15~mbar, the meridional temperature gradient evolves from one season to another. During late northern winter, temperatures were approximately constant from $70^{\circ}$S to $30^{\circ}$N, and then decreased toward the North pole. In mid-spring, temperatures were  decreasing from equator to poles. Near the summer solstice, at 15~mbar, the meridional temperature gradient reversed compared to winter (summer temperatures constant in northern and low southern latitudes then decreasing toward the South Pole), while at 6~mbar,  temperatures globally decrease from the equator to the South pole and $70^{\circ}$N, then increase slightly between $70^{\circ}$N and $90^{\circ}$N. At 15~mbar, most of these changes in the shape of the temperature distribution occur because of the  temperature variations poleward from $60^{\circ}$. At 6~mbar, temperature variations occur mostly in the southern hemisphere at latitudes higher than $40^{\circ}$S, and near the North pole at latitudes higher than $70^{\circ}$N.\\

	\begin{figure}[!h]
		\includegraphics[width=1\columnwidth]{temp_profiles}
		\caption{Temperature variations in the lower stratosphere during the Cassini mission for different latitudes. The blue profiles were measured during northern winter (in 2007). The red profiles were measured in late northern spring (in 2017 for $85^{\circ}$N, in 2016 for the other latitudes). The seasonal temperature variations are observed at most latitudes, and on the whole probed pressure range.}
		\label{fig_grad_saiso_vert}
		\end{figure}

		Figure \ref{fig_grad_saiso_vert} shows the first and the last temperature profiles measured with CIRS nadir far-IR data, for several latitudes. As in Fig. \ref{fig_ev_saiso}, the maximal temperature variations are measured at high southern latitudes for all pressure levels. At $70^{\circ}$S, the temperature decreased by 25~K at 10~mbar. Below 10~mbar the seasonal temperature difference decreases rapidly with increasing pressure until it reaches 10~K at 25~mbar, whereas it is  nearly constant between 5~mbar and 10~mbar. $85^{\circ}$N also exhibits a decrease of the seasonal temperature gradient below the 10~mbar pressure level, although it is less pronounced than near the South pole. At $45^{\circ}$S, the temperature decreased by approximately 10~K from 2007 to 2016, over the whole probed pressure range. At the equator, the temperature varies by -5~K from 2005 to 2016 at 6~mbar and the amplitude of this variation seems to decrease slightly with increasing pressure until it becomes negligible at 25~mbar. However the amplitude of these variations is in the same range as the uncertainty on temperature due to potential $\mathrm{CH_4}$~variations.    \\

\section{Discussion}
\label{sect_discu}
			\subsection{Comparison with previous results}

		\begin{figure}[!h]
			\includegraphics[width=1\columnwidth]{comp_prev_studies_v5}
			\caption{Comparison of nadir FP1 temperatures with previous studies.
				\textit{Top left panel:} Comparison between CIRS nadir FP1 (triangles) and CIRS nadir FP4 temperatures at 6~mbar (circles, \citet{Bampasidis2012}[1], and \citet{Coustenis2016}[2]) in 2010 (cyan) and 2014 (purple).
				\textit{Right panel:} Comparison between temperature profiles from CIRS nadir FP1 observations (thick solid lines), CIRS nadir FP4 observations (thin dot-dashed lines, \citet{Coustenis2016}[2]), and Cassini radio-occultation (thin dashed line, \citet{SchinderFlasarMaroufEtAl2011}[3]). Our results are in good agreement with CIRS FP4 temperatures, but diverge somewhat from radio-occultation profiles with increasing pressure.
				\textit{Bottom left panel:} Comparison between temperatures at 15~mbar from our CIRS FP1 nadir measurements (magenta triangles), Cassini radio-occultations in 2006 and 2007 (cyan circles, \citet{SchinderFlasarMaroufEtAl2011,Schinder2012}, [3], [4]), and the Huygens/HASI measurement in 2005 (yellow diamond, \citet{Fulchignoni2005}, [5]).The dashed magenta line shows the potential effect of the $\mathrm{CH_4}$~variations observed by \citet{Lellouch2014}. If we take into account this effect, the agreement between our data, the radio-occultations and the HASI measurements is good.}
			\label{fig_prev_studies}
		\end{figure}
			Figure \ref{fig_prev_studies} shows a comparison between our results and previous studies where temperatures have been measured in the lower stratosphere at similar epochs, latitudes and pressure levels. In the top left and right panels, our temperature measurements are compared to results from CIRS FP4 nadir observations \citep{Bampasidis2012, Coustenis2016} which probe mainly the 0.1-10~mbar pressure range. In the top left panel, the temperatures measured at 6~mbar by these two types of observations are in good agreement for the two considered epochs (2009-2010 and 2014). We obtain similar meridional gradients with both types of observations, even if FP4 temperatures are obtained from averages of spectra over bins of $10^{\circ}$ of latitudes (except at $70^{\circ}$N and $70^{\circ}$S where the bins are $20^{\circ}$ wide in latitude), whereas the average size in latitude of the field of view of the FP1 detector is $20^{\circ}$. It thus seems than the wider latitudinal size of the FP1 field of view has little effect on our temperature measurements. In the right panel, our temperature profiles are compared to two profiles measured by \citet{Coustenis2016} using CIRS FP4 nadir observations (at $50^{\circ}$S in April 2010, and at $70^{\circ}$S in June 2012), and with Cassini radio-occultations measurements from \citet{SchinderFlasarMaroufEtAl2011,Schinder2012}, which probe the atmosphere from the surface to 0.1~mbar (0 - 300~km). CIRS FP1 and FP4 temperature profiles are in good averall agreement. The profile we measured at $28^{\circ}$S in February 2006 and the corresponding radio-occultation profile are within error bars for pressures lower than 13~mbar, then the difference between them increases up to 8~K at 25~mbar. The bottom left panel of Fig. \ref{fig_prev_studies} shows the radio-occultation temperatures in 2006 and 2007 compared to CIRS nadir FP1 temperatures at 15~mbar, where their sensitivity to the temperature is maximal. Although, the radio-occultations temperatures are systematically higher than the CIRS temperatures by 2~K to 6~K, they follow the same meridional trend. CIRS FP1 temperatures at the equator are also lower than the temperature measured by the HASI instrument at 15~mbar during Huygens descent in Titan's atmosphere in 2005. If we take into account the effect of the spatial variations of $\mathrm{CH_4}$~at 15~mbar observed by \citet{Lellouch2014} by decreasing the $\mathrm{CH_4}$~abundance to 1\% (the lower limit in \citet{Lellouch2014}) in the CIRS FP1 temperature measurements (dashed line in the middle panel of Fig. \ref{fig_prev_studies}), the agreement between the three types of observations is good in the southern hemisphere. The differences between radio-occultations, HASI and CIRS temperatures might also be explained by the difference of vertical resolution. Indeed nadir observations have a vertical resolution in the order of 50~km while radio-occultations and HASI observations have respective vertical resolutions of 1~km and 200~m around 15~mbar.\\

\subsection{Effects of Saturn's eccentricity}
			\begin{figure}[!h]
			\includegraphics[width=1\columnwidth]{eccentricity_equator_free_T0}
			\caption{Temporal evolution of Titan's lower stratospheric temperatures at the equator ($5^{\circ}$N - $5^{\circ}$S) at 6~mbar (left panel) and 15~mbar (right panel), compared with a simple model of the evolution of the temperature as a function of the distance between Titan and the Sun (green line). The reduced $\chi^2$ between this model and the observations is 0.95 at 6~mbar and 1.07 at 15~mbar. The amplitude of the temperature variations at Titan's equator throughout the Cassini mission can be explained by the effect of Saturn's eccentricity.}
			\label{fig_eccentricity}
		\end{figure}
		 Because of Saturn's orbital eccentricity of 0.0565, the distance between Titan and the Sun varies enough to affect significantly the insolation. For instance, throughout the Cassini mission, the solar flux received at the equator has decreased by 19\% because of the eccentricity.  We make a simple model of the evolution of the temperature $T$ at the equator as a function of the distance between Titan and the Sun. In this model we assume that the temperature $T$ at the considered pressure level and at a given time depends only on the absorbed solar flux $F$ and we neglect the radiative exchanges between atmospheric layers:

		 \begin{equation}
		 \epsilon \sigma T^4 = F
		 \end{equation}

		 \noindent where $\epsilon$ is the emissivity of the atmosphere at this pressure level, and $\sigma$ the Stefan-Boltzmann constant.  $T$ can thus be defined as a function of the distance $d$ between Titan and the Sun:

		 \begin{equation}
		 	T^4 = \frac{\alpha L_{\odot}}{16\epsilon\sigma\pi d^2}
		 \label{eq_T_dist}
		 \end{equation}

		 \noindent where $L_\odot$ is the solar power, and $\alpha$ the absorptivity of the atmosphere. If we choose a reference temperature $T_0$ where Titan is at a distance $d_0$ from the Sun, a relation similar  to (\ref{eq_T_dist}) can be written for $T_0$. If we assume $\epsilon$ and $\alpha$ to be constant, $T$ can then be written as:

		 \begin{equation}
		 	T = T_0 \sqrt{\frac{d_0}{d}}
		 \end{equation}

		 Figure \ref{fig_eccentricity} shows a comparison between this model and the temperatures measured between $5^{\circ}$N and $5^{\circ}$S from 2006 to 2016, at 6~mbar and 15~mbar. We choose $T_0$ as the temperature at the beginning of the observations (December 2005/January 2006) which provides the best fit between our model and the observations while being consistent with the observations at the same epoch ($T_0=151.7$~K at 6~mbar, and $T_0=129$~K at 15~mbar). At 6~mbar, we measure a temperature decrease from 2006 to 2016. This is similar to what has been measured at 4~mbar by \citet{Bezard2018} with CIRS mid-IR observations, whereas their radiative-dynamical model predicts a small temperature maximum around the northern spring equinox (2009). At 15~mbar, equatorial temperatures are mostly constant from 2005 to 2016, with a marginal decrease in 2016. Our model predicts temperature variations of 8~K at 6~mbar and 7~K at 15~mbar from 2006 to 2016. Both predictions are consistent with the measurements and with radiative timescales shorter than one Titan year at 6~mbar and 15~mbar, as in \citet{Bezard2018} where they are respectively equal to 0.024~Titan year and 0.06~Titan year. At both pressure levels,  the model captures the magnitude of the temperature change, but does not fully match its timing or shape (especially in 2012-2014), implying that a more sophisticated model is needed. The remaining differences between our model and the temperature measurements could be decreased by adding a temporal lag to our model (2-3~years at 6~mbar and 3-4~years at 15~mbar), but the error bars on the temperature measurements are too large to constrain the lag to a value statistically distinct from zero.  Even with this potential lag, the agreement between the model and the temperatures measured at 6~mbar shows that the amplitude of the temporal evolution throughout the Cassini mission may be explained by the effects of Saturn's eccentricity. At 15~mbar, given the error bars and the lack of further far-IR temperature measurements at the equator in 2016 and 2017, it remains difficult to draw a definitive conclusion about the influence of Saturn's eccentricity at this pressure level.\\

	\subsection{Implication for radiative and dynamical processes of the lower stratosphere}

		In  Section \ref{sect_res}, we showed that in the lower stratosphere, the seasonal evolution of the temperature is maximal at high latitudes, especially at the South Pole. At 15~mbar, the strong cooling of high southern latitudes started in 2012, simultaneously with the increase in $\mathrm{C_2N_2}$, $\mathrm{C_4H_2}$, and $\mathrm{C_3H_4}$~abundances measured at the same latitudes and pressure-level in \citet{Sylvestre2018}. We also show that this cooling affects the atmosphere at least down to the 25~mbar pressure level (altitude of 70~km). The enrichment of the gases and cooling are consistent with the onset of a subsidence above the South Pole during autumn, as predicted by GCMs \citep{Newman2011, Lebonnois2012a}, and inferred from previous CIRS observations at higher altitudes \citep{Teanby2012, Vinatier2015, Coustenis2016}. As Titan's atmospheric circulation transitions from two equator-to-poles cells (with upwelling above the equator and subsidence above the poles) to a single pole-to-pole cell (with a descending branch above South Pole), this subsidence drags downward photochemical species created at higher altitudes toward the lower stratosphere. \citet{Teanby2017} showed that enrichment in  trace gases may be so strong that their cooling effect combined with the insolation decrease may exceed the adiabatic heating between 0.3~mbar and 10~mbar (100 - 250~km). Our observations show that this phenomena may be at play down as deep as 25~mbar.\\

        We compare retrieved temperature fields with results of simulations from IPSL 3D-GCM \citep{Lebonnois2012a} with an updated radiative transfer scheme \citep{Vatantd'Ollone2017} now based on a flexible \textit{correlated-k} method and up-to-date gas spectroscopic data \citep{Rothman2013}. It does not take into account the radiative feedback of the enrichment in hazes and trace gases in the polar regions, but it nevertheless appears that there is a good agreement in terms of seasonal cycle between the model and the observations. As shown in Figure \ref{fig_var_saiso}, at 6~mbar meridional distributions and values of temperatures in the model match well the observations. It can be pointed out that in both model and observations there is a noticeable asymmetry between high southern latitudes where the temperature decreases rapidly from the equinox to winter, and high northern latitudes which evolve more slowly from winter to summer. For instance, in both CIRS data and model, between 2007 and 2013 at 6~mbar and $70^{\circ}$N the atmosphere has warmed by only about 2~K, while in the meantime at $70^{\circ}$S it has cooled by about 10-15~K. This is consistent with an increase of radiative timescales at high northern latitudes (due to lower temperatures, \citet{Achterberg2011}) which would remain cold for approximately one season even after the return of sunlight. Figure \ref{fig_map_temp_gcm70N} shows the temporal evolution of the temperature at $70^{\circ}$N over one Titan year in the lower stratosphere in the GCM simulations and also emphasizes this asymmetry between the ingress and egress of winter at high latitudes. In Figure \ref{fig_var_saiso}, at 15~mbar modeled temperatures underestimate the observations by roughly 5-10~K, certainly due to a lack of infrared coolers such as clouds condensates \citep{Jennings2015}. However, observations and simulations exhibit similar meridional temperature gradients for the three studied epochs, and similar seasonal temperature evolution. For instance, in 2016-2017 we measured a temperature gradient of -11~K between the North and South Pole, whereas GCM simulations predict a temperature gradient of -12~K. At $70^{\circ}$S, temperature decreases by 10~K between 2007 and 2016-2017 in the GCM and in our observations. Besides, at 15~mbar, the seasonal behaviour remains the same as at 6~mbar, although more damped. Indeed comparison with GCM results also supports the idea that the seasonal effects due to the variations of insolation are damped with increasing depth in the lower stratosphere and ultimately muted below 25 mbar, as displayed in Figure \ref{fig_map_temp_gcm70N}. At lower altitudes the seasonal cycle of temperature at high latitudes is even inverted with temperatures increasing in the winter and decreasing in summer. Indeed at these altitudes, due to the radiative timescales exceeding one Titan year, temperature is no more sensitive to the seasonal variations of solar forcing, but to the interplay of ascending and descending large scale vertical motions of the pole-to-pole cell, inducing respectively adiabatic heating above winter pole and cooling above summer pole, as previously discussed in \citet{Lebonnois2012a}.

Further analysis of simulations – not presented here - also show that after 2016, temperatures at high southern latitudes began to slightly increase again at 6~mbar, which is consistent with observations, whereas at 15~mbar no change in the trend is observed, certainly due to a phase shift of the seasonal cycle between the two altitudes induced by the difference of radiative timescales, which is also illustrated in Figure \ref{fig_map_temp_gcm70N}.  \\

			\begin{figure}[!h]
			\includegraphics[width=1\columnwidth]{Map_Temperature_70N}
			\caption{Seasonal evolution of Titan's lower stratospheric temperatures modeled by the IPSL 3D-GCM at 70$^{\circ}$N - between 5~mbar and 50~mbar, starting at northern spring equinox. In the pressure range probed by the CIRS far-IR observations (from 6~mbar to 25~mbar), there is a strong asymmetry between the rapid temperature changes after autumn equinox ($L_S = 180^{\circ}$) and the slow evolution of the thermal structure after spring equinox ($L_S = 0^{\circ}$). }
			\label{fig_map_temp_gcm70N}
		\end{figure}

		We  also show in Figure \ref{fig_grad_saiso_vert} that at high southern latitudes, from 6 to 10~mbar seasonal temperature variations are approximately constant with pressure and can be larger than 10~K, whereas they decrease with increasing pressure below 10~mbar. This transition at 10~mbar may be caused by the increase of radiative timescales in the lower stratosphere. \citet{Strobel2010} estimated that the radiative timescale increases from one Titan season at 6~mbar to half a Titan year at 12~mbar. It can thus be expected that this region should be a transition zone between regions of the atmosphere where the atmospheric response to the seasonal insolation variations is significant and comes with little lag, to regions of the atmosphere where they are negligible.  However, this transition should be observable at other latitudes such as $45^{\circ}$S, whereas Figure \ref{fig_grad_saiso_vert} shows a seasonal gradient constant with pressure at this latitude. Furthermore, in \citet{Bezard2018}, the authors show that the method used to estimate radiative timescales in \citet{Strobel2010} tends to overestimate them, and that in their model radiative timescales are less than a Titan season down to the 35~mbar pressure level, which is more consistent with the seasonal variations measured at $45^{\circ}$S.\\

        The 10~mbar transition can also be caused by the interplay between photochemical, radiative and dynamical processes at high latitudes. Indeed, as photochemical species are transported downward by the subsidence above the autumn/winter pole, build up and cool strongly the lower atmosphere, the condensation level of species such as HCN, $\mathrm{HC_3N}$, $\mathrm{C_4H_2}$ or $\mathrm{C_6H_6}$ may be shifted upward, toward the 10~mbar level. Hence, below this pressure level, the volume mixing ratios of these gases would rapidly decrease, along with their cooling effect. Many observations, especially during the Cassini mission showed that during winter and autumn, polar regions host clouds composed of ices of photochemical species. For instance, the "haystack" feature showed in Fig. \ref{fig_spec} has been studied at both poles in  \citet{Coustenis1999,Jennings2012,Jennings2015},  and is attributed to a mixture of condensates, possibly of nitrile origin. Moreover, HCN ice has been measured in the southern polar cloud observed by \citet{deKok2014} with Cassini/VIMS observations. $\mathrm{C_6H_6}$ ice has also been detected by \citet{Vinatier2018} in CIRS observations of the South Pole. The condensation curve for $\mathrm{C_4H_2}$~in \citet{Barth2017} is also consistent with the formation of  $\mathrm{C_4H_2}$~ice around 10~mbar with the temperatures we measured at $70^{\circ}$S in 2016. These organic ices may also have a cooling effect themselves as \citet{Bezard2018} showed that at 9~mbar, the nitrile haze measured by \citet{Anderson2011} contributes to the cooling with an intensity comparable to the contribution of  gases such as $\mathrm{C_2H_2}$ and $\mathrm{C_2H_6}$.  \\

\section{Conclusion}

	In this paper, we analysed all the available nadir far-IR CIRS observations to measure Titan's lower stratospheric temperatures (6~mbar - 25~mbar) throughout the 13 years of the Cassini mission, from northern winter to summer solstice. In this pressure range, significant temperature changes occur from one season to another. Temperatures evolve moderately at low and mid-latitudes (less than 10~K between 6 and 15~mbar).  At the equator, at 6~mbar we measure a temperature decrease mostly due to Saturn's eccentricity. Seasonal temperature changes are maximal at high latitudes, especially in the southern hemisphere where they reach up to -19~K at $70^{\circ}$S between summer (2007) and late autumn (2016) at 15~mbar. The strong seasonal evolution of high southern latitudes is due to a complex interplay between photochemistry, atmospheric dynamics  with the downwelling above the autumn/winter poles, radiative processes with a large contribution of the gases transported toward the lower stratosphere, and possibly condensation due to the cold autumn polar temperatures and strong enrichments in trace gases.\\

Recent GCM simulations show a good agreement with the observed seasonal variations in this pressure range, even though these simulations do not include coupling with variations of opacity sources. In particular at high latitudes, the fast decrease of temperatures when entering winter and slower increase when getting into summer is well reproduced in these simulations.

\section*{Acknowledgements}
	This research was funded by the UK Sciences and Technology Facilities Research council (grant number ST/MOO7715/1) and the Cassini project. JVO and SL acknowledge support from the Centre National d'Etudes Spatiales (CNES). GCM simulations have been performed thanks to computation facilities provided by the Grand Équipement National de Calcul Intensif (GENCI) on the \textit{Occigen/CINES} cluster (allocation A0040110391).
This research made use of Astropy, a community-developed core Python package for Astronomy \citep{2013A&A...558A..33A}, and matplotlib, a Python library for publication quality graphics \citep{Hunter:2007}

\section*{Appendix. Cassini/CIRS Datasets analysed in this study}	%

	\onecolumn
	\begin{longtable}[!h]{lcccc}
	\caption{\label{table_obs}Far-IR CIRS datasets presented in this study. N stands for the number of spectra measured during the acquisition. FOV is the field of view. The asterisk denotes datasets where two different latitudes were observed. }\\
	\hline
	\hline
	 Observations & Date & N & Latitude ($^{\circ}$N) & FOV ($^{\circ}$)\\
	\hline

		CIRS\_00BTI\_FIRNADCMP001\_PRIME & 12 Dec. 2004 &  224 & 16.4 & 20.3\\
		CIRS\_003TI\_FIRNADCMP002\_PRIME & 15 Feb. 2005 &  180 & -18.7 & 18.5\\
		CIRS\_005TI\_FIRNADCMP002\_PRIME & 31 Mar. 2005 &  241 & -41.1 & 25.7\\
		CIRS\_005TI\_FIRNADCMP003\_PRIME & 01 Apr. 2005 &  240 & 47.8 & 28.5\\
		CIRS\_006TI\_FIRNADCMP002\_PRIME & 16 Apr. 2005 &  178 & 54.7 & 29.9\\
		CIRS\_009TI\_COMPMAP002\_PRIME & 06 Jun. 2005 &  184 & -89.7 & 21.1\\
		CIRS\_013TI\_FIRNADCMP003\_PRIME & 21 Aug. 2005 &  192 & 30.1 & 15.5\\
		CIRS\_013TI\_FIRNADCMP004\_PRIME & 22 Aug. 2005 &  248 & -53.7 & 25.0\\
		CIRS\_017TI\_FIRNADCMP003\_PRIME & 28 Oct. 2005 &  119 & 20.1 & 19.8\\
		CIRS\_019TI\_FIRNADCMP002\_PRIME & 26 Dec. 2005 &  124 & -0.0 & 17.6\\
		CIRS\_020TI\_FIRNADCMP002\_PRIME & 14 Jan. 2006 &  107 & 19.5 & 19.7\\
		CIRS\_021TI\_FIRNADCMP002\_PRIME & 27 Feb. 2006 &  213 & -30.2 & 22.5\\
		CIRS\_022TI\_FIRNADCMP003\_PRIME & 18 Mar. 2006 &  401 & -0.4 & 18.4\\
		CIRS\_022TI\_FIRNADCMP008\_PRIME & 19 Mar. 2006 &  83 & 25.3 & 24.1\\
		CIRS\_023TI\_FIRNADCMP002\_PRIME & 01 May 2006 &  215 & -35.0 & 27.8\\
		CIRS\_024TI\_FIRNADCMP003\_PRIME & 19 May 2006 &  350 & -15.5 & 21.6\\
		CIRS\_025TI\_FIRNADCMP002\_PRIME & 02 Jul. 2006 &  307 & 25.1 & 21.7\\
		CIRS\_025TI\_FIRNADCMP003\_PRIME & 01 Jul. 2006 &  190 & 39.7 & 25.6\\
		CIRS\_028TI\_FIRNADCMP003\_PRIME & 07 Sep. 2006 &  350 & 29.7 & 19.7\\
		CIRS\_029TI\_FIRNADCMP003\_PRIME & 23 Sep. 2006 &  312 & 9.5 & 19.4\\
		CIRS\_030TI\_FIRNADCMP002\_PRIME & 10 Oct. 2006 &  340 & -59.1 & 23.4\\
		CIRS\_030TI\_FIRNADCMP003\_PRIME & 09 Oct. 2006 &  286 & 33.9 & 19.9\\
		CIRS\_031TI\_COMPMAP001\_VIMS & 25 Oct. 2006 &  160 & -14.5 & 16.3\\
		CIRS\_036TI\_FIRNADCMP002\_PRIME & 28 Dec. 2006 &  136 & -89.1 & 12.6\\
		CIRS\_036TI\_FIRNADCMP003\_PRIME & 27 Dec. 2006 &  321 & 78.6 & 21.0\\
		CIRS\_037TI\_FIRNADCMP001\_PRIME & 12 Jan. 2007 &  161 & 75.2 & 19.1\\
		CIRS\_037TI\_FIRNADCMP002\_PRIME & 13 Jan. 2007 &  107 & -70.3 & 20.6\\
		CIRS\_038TI\_FIRNADCMP001\_PRIME & 28 Jan. 2007 &  254 & 86.3 & 16.7\\
		CIRS\_038TI\_FIRNADCMP002\_PRIME & 29 Jan. 2007 &  254 & -39.7 & 22.0\\
		CIRS\_039TI\_FIRNADCMP002\_PRIME & 22 Feb. 2007 &  23 & 69.9 & 21.2\\
		CIRS\_040TI\_FIRNADCMP001\_PRIME & 09 Mar. 2007 &  159 & -49.2 & 21.1\\
		CIRS\_040TI\_FIRNADCMP002\_PRIME & 10 Mar. 2007 &  109 & 88.8 & 13.3\\
		CIRS\_041TI\_FIRNADCMP002\_PRIME & 26 Mar. 2007 &  102 & 61.2 & 19.3\\
		CIRS\_042TI\_FIRNADCMP001\_PRIME & 10 Apr. 2007 &  103 & -60.8 & 26.0\\
		CIRS\_042TI\_FIRNADCMP002\_PRIME & 11 Apr. 2007 &  272 & 71.5 & 22.6\\
		CIRS\_043TI\_FIRNADCMP001\_PRIME & 26 Apr. 2007 &  263 & -51.4 & 24.7\\
		CIRS\_043TI\_FIRNADCMP002\_PRIME & 27 Apr. 2007 &  104 & 77.1 & 20.0\\
		CIRS\_044TI\_FIRNADCMP002\_PRIME & 13 May 2007 &  104 & -0.5 & 18.8\\
		CIRS\_045TI\_FIRNADCMP001\_PRIME & 28 May 2007 &  231 & -22.3 & 22.6\\
		CIRS\_045TI\_FIRNADCMP002\_PRIME & 29 May 2007 &  346 & 52.4 & 29.5\\
		CIRS\_046TI\_FIRNADCMP001\_PRIME & 13 Jun. 2007 &  60 & 17.6 & 28.6\\
		CIRS\_046TI\_FIRNADCMP002\_PRIME & 14 Jun. 2007 &  102 & -20.8 & 19.0\\
		CIRS\_047TI\_FIRNADCMP001\_PRIME & 29 Jun. 2007 &  204 & 9.8 & 23.2\\
		CIRS\_047TI\_FIRNADCMP002\_PRIME & 30 Jun. 2007 &  238 & 20.1 & 23.7\\
		CIRS\_048TI\_FIRNADCMP001\_PRIME & 18 Jul. 2007 &  96 & -34.8 & 31.4\\
		CIRS\_048TI\_FIRNADCMP002\_PRIME & 19 Jul. 2007 &  260 & 49.5 & 35.8\\
		CIRS\_050TI\_FIRNADCMP001\_PRIME & 01 Oct. 2007 &  144 & -10.1 & 23.8\\
		CIRS\_050TI\_FIRNADCMP002\_PRIME & 02 Oct. 2007 &  106 & 29.9 & 19.7\\
		CIRS\_052TI\_FIRNADCMP002\_PRIME & 19 Nov. 2007 &  272 & 40.3 & 26.5\\
		CIRS\_053TI\_FIRNADCMP001\_PRIME & 04 Dec. 2007 &  223 & -40.2 & 25.8\\
		CIRS\_053TI\_FIRNADCMP002\_PRIME & 05 Dec. 2007 &  102 & 59.4 & 28.3\\
		CIRS\_054TI\_FIRNADCMP002\_PRIME & 21 Dec. 2007 &  107 & 60.4 & 21.1\\
		CIRS\_055TI\_FIRNADCMP001\_PRIME & 05 Jan. 2008 &  190 & 18.7 & 30.5\\
		CIRS\_055TI\_FIRNADCMP002\_PRIME & 06 Jan. 2008 &  284 & 44.6 & 22.2\\
		CIRS\_059TI\_FIRNADCMP001\_PRIME & 22 Feb. 2008 &  172 & -24.9 & 20.7\\
		CIRS\_059TI\_FIRNADCMP002\_PRIME & 23 Feb. 2008 &  98 & 17.1 & 20.0\\
		CIRS\_062TI\_FIRNADCMP002\_PRIME & 25 Mar. 2008 &  115 & 59.3 & 17.1\\
		CIRS\_067TI\_FIRNADCMP002\_PRIME & 12 May 2008 &  286 & 29.5 & 21.0\\
		CIRS\_069TI\_FIRNADCMP001\_PRIME & 27 May 2008 &  112 & -44.6 & 27.3\\
		CIRS\_069TI\_FIRNADCMP002\_PRIME & 28 May 2008 &  112 & 9.5 & 19.3\\
		CIRS\_093TI\_FIRNADCMP002\_PRIME & 20 Nov. 2008 &  161 & 43.7 & 21.1\\
		CIRS\_095TI\_FIRNADCMP001\_PRIME & 05 Dec. 2008 &  213 & -14.0 & 20.7\\
		CIRS\_097TI\_FIRNADCMP001\_PRIME & 20 Dec. 2008 &  231 & -10.9 & 23.7\\
		CIRS\_106TI\_FIRNADCMP001\_PRIME & 26 Mar. 2009 &  165 & -60.3 & 19.2\\
		CIRS\_107TI\_FIRNADCMP002\_PRIME & 27 Mar. 2009 &  164 & 33.5 & 30.4\\
		CIRS\_110TI\_FIRNADCMP001\_PRIME & 06 May 2009 &  282 & -68.1 & 25.7\\
		CIRS\_111TI\_FIRNADCMP002\_PRIME & 22 May 2009 &  168 & -27.1 & 23.1\\
		CIRS\_112TI\_FIRNADCMP001\_PRIME & 06 Jun. 2009 &  218 & 48.7 & 21.0\\
		CIRS\_112TI\_FIRNADCMP002\_PRIME & 07 Jun. 2009 &  274 & -58.9 & 20.2\\
		CIRS\_114TI\_FIRNADCMP001\_PRIME & 09 Jul. 2009 &  164 & -71.4 & 25.4\\
		CIRS\_115TI\_FIRNADCMP001\_PRIME & 24 Jul. 2009 &  146 & 50.7 & 20.1\\
		CIRS\_119TI\_FIRNADCMP002\_PRIME & 12 Oct. 2009 &  166 & 0.4 & 18.3\\
		CIRS\_122TI\_FIRNADCMP001\_PRIME & 11 Dec. 2009 &  212 & 39.8 & 24.7\\
		CIRS\_123TI\_FIRNADCMP002\_PRIME & 28 Dec. 2009 &  186 & -46.1 & 22.3\\
		CIRS\_124TI\_FIRNADCMP002\_PRIME & 13 Jan. 2010 &  272 & -1.2 & 19.0\\
		CIRS\_125TI\_FIRNADCMP001\_PRIME & 28 Jan. 2010 &  156 & 39.9 & 27.5\\
		CIRS\_125TI\_FIRNADCMP002\_PRIME & 29 Jan. 2010 &  280 & -44.9 & 27.3\\
		CIRS\_129TI\_FIRNADCMP001\_PRIME & 05 Apr. 2010 &  119 & -45.1 & 28.2\\
		CIRS\_131TI\_FIRNADCMP001\_PRIME & 19 May 2010 &  188 & -30.0 & 22.1\\
		CIRS\_131TI\_FIRNADCMP002\_PRIME & 20 May 2010 &  229 & -19.8 & 21.5\\
		CIRS\_132TI\_FIRNADCMP002\_PRIME & 05 Jun. 2010 &  167 & 49.4 & 27.4\\
		CIRS\_133TI\_FIRNADCMP001\_PRIME & 20 Jun. 2010 &  187 & -49.7 & 36.1\\
		CIRS\_134TI\_FIRNADCMP001\_PRIME & 06 Jul. 2010 &  251 & -10.0 & 20.0\\
		CIRS\_138TI\_FIRNADCMP001\_PRIME & 24 Sep. 2010 &  190 & -30.1 & 21.2\\
		CIRS\_139TI\_COMPMAP001\_PRIME* & 14 Oct. 2010 &  132 & -70.9 & 20.6\\
		CIRS\_139TI\_COMPMAP001\_PRIME* & 14 Oct. 2010 &  108 & -53.8 & 16.7\\
		CIRS\_148TI\_FIRNADCMP001\_PRIME & 08 May 2011 &  200 & -10.0 & 18.3\\
		CIRS\_153TI\_FIRNADCMP001\_PRIME & 11 Sep. 2011 &  227 & 9.9 & 19.0\\
		CIRS\_158TI\_FIRNADCMP501\_PRIME & 13 Dec. 2011 &  369 & -29.9 & 24.7\\
		CIRS\_159TI\_FIRNADCMP001\_PRIME & 02 Jan. 2012 &  275 & -42.2 & 23.7\\
		CIRS\_160TI\_FIRNADCMP001\_PRIME & 29 Jan. 2012 &  322 & -40.0 & 21.7\\
		CIRS\_160TI\_FIRNADCMP002\_PRIME & 30 Jan. 2012 &  280 & -0.2 & 18.3\\
		CIRS\_161TI\_FIRNADCMP001\_PRIME & 18 Feb. 2012 &  121 & 9.9 & 18.4\\
		CIRS\_161TI\_FIRNADCMP002\_PRIME & 19 Feb. 2012 &  89 & -15.0 & 17.3\\
		CIRS\_166TI\_FIRNADCMP001\_PRIME & 22 May 2012 &  318 & -19.9 & 19.9\\
		CIRS\_167TI\_FIRNADCMP002\_PRIME & 07 Jun. 2012 &  293 & -45.4 & 21.7\\
		CIRS\_169TI\_FIRNADCMP001\_PRIME & 24 Jul. 2012 &  258 & -9.7 & 20.7\\
		CIRS\_172TI\_FIRNADCMP001\_PRIME & 26 Sep. 2012 &  282 & 44.9 & 18.5\\
		CIRS\_172TI\_FIRNADCMP002\_PRIME & 26 Sep. 2012 &  270 & -70.4 & 23.2\\
		CIRS\_174TI\_FIRNADCMP002\_PRIME & 13 Nov. 2012 &  298 & -71.8 & 21.8\\
		CIRS\_175TI\_FIRNADCMP002\_PRIME & 29 Nov. 2012 &  299 & -59.9 & 19.3\\
		CIRS\_185TI\_FIRNADCMP001\_PRIME & 05 Apr. 2013 &  244 & 15.0 & 20.1\\
		CIRS\_185TI\_FIRNADCMP002\_PRIME & 06 Apr. 2013 &  303 & -88.9 & 16.8\\
		CIRS\_190TI\_FIRNADCMP001\_PRIME & 23 May 2013 &  224 & -0.2 & 25.6\\
		CIRS\_190TI\_FIRNADCMP002\_PRIME & 24 May 2013 &  298 & -45.0 & 20.0\\
		CIRS\_194TI\_FIRNADCMP001\_PRIME & 10 Jul. 2013 &  186 & 30.0 & 19.7\\
		CIRS\_195TI\_FIRNADCMP001\_PRIME & 25 Jul. 2013 &  186 & 19.6 & 24.5\\
		CIRS\_197TI\_FIRNADCMP001\_PRIME & 11 Sep. 2013 &  330 & 60.5 & 19.4\\
		CIRS\_198TI\_FIRNADCMP001\_PRIME & 13 Oct. 2013 &  187 & 88.9 & 8.7\\
		CIRS\_198TI\_FIRNADCMP002\_PRIME & 14 Oct. 2013 &  306 & -69.8 & 24.0\\
		CIRS\_199TI\_FIRNADCMP001\_PRIME & 30 Nov. 2013 &  329 & 68.4 & 23.9\\
		CIRS\_200TI\_FIRNADCMP001\_PRIME & 01 Jan. 2014 &  187 & 49.9 & 19.6\\
		CIRS\_200TI\_FIRNADCMP002\_PRIME & 02 Jan. 2014 &  210 & -59.8 & 21.3\\
		CIRS\_201TI\_FIRNADCMP001\_PRIME & 02 Feb. 2014 &  329 & 19.9 & 26.8\\
		CIRS\_201TI\_FIRNADCMP002\_PRIME & 03 Feb. 2014 &  234 & -39.6 & 20.9\\
		CIRS\_203TI\_FIRNADCMP001\_PRIME & 07 Apr. 2014 &  187 & 75.0 & 18.0\\
		CIRS\_203TI\_FIRNADCMP002\_PRIME & 07 Apr. 2014 &  239 & 0.5 & 27.5\\
		CIRS\_204TI\_FIRNADCMP002\_PRIME & 18 May 2014 &  199 & 0.4 & 27.0\\
		CIRS\_205TI\_FIRNADCMP001\_PRIME & 18 Jun. 2014 &  144 & -45.1 & 20.5\\
		CIRS\_205TI\_FIRNADCMP002\_PRIME & 18 Jun. 2014 &  161 & 30.3 & 19.1\\
		CIRS\_206TI\_FIRNADCMP001\_PRIME & 19 Jul. 2014 &  181 & -50.3 & 17.8\\
		CIRS\_206TI\_FIRNADCMP002\_PRIME & 20 Jul. 2014 &  161 & 30.6 & 18.4\\
		CIRS\_207TI\_FIRNADCMP001\_PRIME & 20 Aug. 2014 &  179 & -70.0 & 17.8\\
		CIRS\_207TI\_FIRNADCMP002\_PRIME & 21 Aug. 2014 &  163 & 79.7 & 17.6\\
		CIRS\_208TI\_FIRNADCMP001\_PRIME & 21 Sep. 2014 &  329 & -80.0 & 15.6\\
		CIRS\_208TI\_FIRNADCMP002\_PRIME & 22 Sep. 2014 &  175 & 60.5 & 17.8\\
		CIRS\_209TI\_FIRNADCMP001\_PRIME & 23 Oct. 2014 &  181 & -35.2 & 17.7\\
		CIRS\_209TI\_FIRNADCMP002\_PRIME & 24 Oct. 2014 &  233 & 50.5 & 18.5\\
		CIRS\_210TI\_FIRNADCMP001\_PRIME & 10 Dec. 2014 &  329 & -70.3 & 25.2\\
		CIRS\_210TI\_FIRNADCMP002\_PRIME & 11 Dec. 2014 &  237 & -19.6 & 27.6\\
		CIRS\_211TI\_FIRNADCMP001\_PRIME & 11 Jan. 2015 &  225 & 19.6 & 25.0\\
		CIRS\_211TI\_FIRNADCMP002\_PRIME & 12 Jan. 2015 &  258 & 40.0 & 19.3\\
		CIRS\_212TI\_FIRNADCMP002\_PRIME & 13 Feb. 2015 &  257 & -40.0 & 30.1\\
		CIRS\_213TI\_FIRNADCMP001\_PRIME & 16 Mar. 2015 &  187 & -31.6 & 19.6\\
		CIRS\_213TI\_FIRNADCMP002\_PRIME & 16 Mar. 2015 &  258 & 23.4 & 20.5\\
		CIRS\_215TI\_FIRNADCMP001\_PRIME & 07 May 2015 &  250 & -50.0 & 31.0\\
		CIRS\_215TI\_FIRNADCMP002\_PRIME & 08 May 2015 &  232 & -30.0 & 21.7\\
		CIRS\_218TI\_FIRNADCMP001\_PRIME & 06 Jul. 2015 &  249 & -20.0 & 19.9\\
		CIRS\_218TI\_FIRNADCMP002\_PRIME & 07 Jul. 2015 &  232 & -40.0 & 25.2\\
		CIRS\_222TI\_FIRNADCMP001\_PRIME & 28 Sep. 2015 &  125 & 30.0 & 21.7\\
		CIRS\_222TI\_FIRNADCMP002\_PRIME & 29 Sep. 2015 &  233 & -0.1 & 18.6\\
		CIRS\_230TI\_FIRNADCMP001\_PRIME & 15 Jan. 2016 &  282 & -15.0 & 19.5\\
		CIRS\_231TI\_FIRNADCMP001\_PRIME & 31 Jan. 2016 &  254 & 15.0 & 19.6\\
		CIRS\_231TI\_FIRNADCMP002\_PRIME & 01 Feb. 2016 &  236 & 0.4 & 18.9\\
		CIRS\_232TI\_FIRNADCMP001\_PRIME & 16 Feb. 2016 &  249 & -50.2 & 24.5\\
		CIRS\_232TI\_FIRNADCMP002\_PRIME & 17 Feb. 2016 &  92 & -19.8 & 21.5\\
		CIRS\_234TI\_FIRNADCMP001\_PRIME & 04 Apr. 2016 &  328 & 19.8 & 24.7\\
		CIRS\_235TI\_FIRNADCMP001\_PRIME & 06 May 2016 &  163 & -60.0 & 19.7\\
		CIRS\_235TI\_FIRNADCMP002\_PRIME & 07 May 2016 &  221 & 15.7 & 20.1\\
		CIRS\_236TI\_FIRNADCMP001\_PRIME & 07 Jun. 2016 &  88 & -70.5 & 20.5\\
		CIRS\_236TI\_FIRNADCMP002\_PRIME & 07 Jun. 2016 &  238 & 60.8 & 20.0\\
		CIRS\_238TI\_FIRNADCMP002\_PRIME & 25 Jul. 2016 &  220 & 15.4 & 20.5\\
		CIRS\_248TI\_FIRNADCMP001\_PRIME & 13 Nov. 2016 &  185 & -88.9 & 18.3\\
		CIRS\_248TI\_FIRNADCMP002\_PRIME & 14 Nov. 2016 &  186 & 30.3 & 17.4\\
		CIRS\_250TI\_FIRNADCMP002\_PRIME & 30 Nov. 2016 &  219 & -19.8 & 28.4\\
		CIRS\_259TI\_COMPMAP001\_PIE & 01 Feb. 2017 &  302 & -69.0 & 20.6\\
		CIRS\_270TI\_FIRNADCMP001\_PRIME & 21 Apr. 2017 &  166 & -74.7 & 25.4\\
		CIRS\_283TI\_COMPMAP001\_PRIME* & 10 Jul. 2017 &  114 & 60.0 & 26.5\\
		CIRS\_283TI\_COMPMAP001\_PRIME* & 10 Jul. 2017 &  134 & 67.5 & 24.7\\
		CIRS\_287TI\_COMPMAP001\_PIE & 11 Aug. 2017 &  305 & 88.9 & 9.3\\
		CIRS\_288TI\_COMPMAP002\_PIE & 11 Aug. 2017 &  269 & 66.7 & 23.7\\
		CIRS\_292TI\_COMPMAP001\_PRIME & 12 Sep. 2017 &  192 & 70.4 & 19.2\\

	\hline
\end{longtable}

\twocolumn
\section*{References}
\bibliographystyle{elsarticle-harv}

redpajama_set_name: RedPajamaArXiv


Several People's Liberation Army Navy Houbei missile boats.
The following is from the recently released written testimony from Jesse Karotkin is the Senior Intelligence Officer (SIO) for China at the Office of Naval Intelligence (ONI) before the U.S. China Economic and Security Review Commission on Jan. 30, 2014.
At the dawn of the 21st Century, the People's Liberation Army Navy (PLA(N)) remained largely a littoral force. Though China's maritime interests were rapidly changing, the vast majority of its naval platforms offered very limited capability and endurance, particularly in blue water. Over the past 15 years the PLA(N) has carried out an ambitious modernization effort, resulting in a more technologically advanced and flexible force.
This transformation is evident not only the PLA(N)'s Gulf of Aden counter-piracy presence, which is now in its sixth year, but also in the navy's more advanced regional operations and exercises. In contrast to its narrow focus a just decade ago, the PLA(N) is evolving to meet a wide range of missions including conflict with Taiwan, enforcement of maritime claims, protection of economic interests, as well as counter- piracy and humanitarian missions.
The PLA(N) currently possesses approximately 77 principal surface combatants, more than 60 submarines, 55 medium and large amphibious ships, and roughly 85 missile-equipped small combatants.
Although overall order-of-battle has remained relatively constant in recent years, the PLA(N) is rapidly retiring legacy combatants in favor of larger, multi-mission ships, equipped with advanced anti-ship, anti-air, and anti-submarine weapons and sensors. During 2013 alone, over fifty naval ships were laid down, launched, or commissioned, with a similar number expected in 2014. Major qualitative improvements are occurring within naval aviation and the submarine force, which are increasingly capable of striking targets hundreds of miles from the Chinese mainland.


Yet another advantage of being a soccer fan–our March Madness arrives a month early. The knockout phase of the Champions League starts today, with a sweet collection of 16 teams remaining. If you were one of the fans that was caught up by the World Cup last summer, but haven't watched a game since Spain-Netherlands, now is the time to tune back in.
See below where and when to tune in. US-based fans, set your DVRs accordingly–or make plans to duck out of whatever responsibilities you may have in the afternoons (all matches kickoff at 20:45 CET = 2:45pmET/11:45amPT).
For tomorrow's two games, see here for a preview of Milan-Tottenham by our resident Spurs fan, and here for a preview of Valencia-Schalke by Sean (who honestly didn't know much about either side until researching this piece).
Here are a bunch of matches to watch over the next few days–a few on Saturday, one Sunday, and one Monday. Which takes you right up to Tuesday…and the start of the Champions League Round of 16. Bananas.
As always, all times ET, and a hat tip to WaPo's Soccer Insider for posting the weekend listings every week.
England, Manchester United-Manchester City 7:30am FSC: Manchester derby! Early in the morning! This is a big one–City is but 5 points behind Man U, after the latter finally lost last weekend. See here for squad sheets. Also, Mancini denies he is Italian.
England, Arsenal-Wolves 10am ESPN2: Why? Because we have so many Gunners fans among us, because it will be interesting to see how they rebound after the debacle last Saturday at Newcastle, and because it will be interesting to see if Wolves can pull off two upsets in a row. They just might.
"If Villa comes anywhere near my touchline during the game, I might just bite him"
England, QPR-Nottingham Forest 8:30a FSP: Take a peak at the Championship. Why? Why not? Well, these two are currently #1 and #2 in the table, so there's a good chance one or both will be in the Premier League next year.
England, Fulham-Chelsea 3 p.m. ESPN2: Torres, Demspey & Dembele, Valentine's Day..
There is a full slate of meaningless international friendlies today, with the European and South American powers in action in some attractive matchups (Guardian blogger Paolo Bandini, in a bit of hyperbole: "Is this the best night of friendlies ever?"). Moreover, most of those matches available for viewing here in the US (at least on ESPN3).
We may peek in on France-Brazil, Argentina-Portugal, or even Denmark-England. Especially since the storyline for that latter one, at least from the English point of view, seems to be young Jack Wilshere's first start. Fabio Capello did nothing to manage expectations of a nation looking for yet another savior by mentioning "Baresi, Maldini, Raúl" when asked about Wilshere.
Update: For reference, here are the squad lists for a few of the matches, which are now in progress.
France: Lloris; Sagna, Rami, Mexes, Abidal – A Diarra, M'vila – Menez, Gourcuff, Malouda – Benzema.
Denmark: Sorensen, Christian Poulsen, Jorgensen, Agger, Simon Poulsen, Jacobsen, Kvist, Eriksen, Krohn-Delhi, Rommedahl, Bendtner.
Subs: Lindegaard, Wass, Kjaer, Silberbauer, Schone, Vingaard, Junker, Lorentzen, Enevoldsen, Pedersen.
England:Hart, Johnson, Dawson, Terry, Ashley Cole, Lampard, Wilshere, Walcott, Rooney, Milner, Bent.
But will King Kenny be this happy at Stamford Bridge this Sunday?
A handful of viewing options for the weekend, culled from the full set of televised matches. If you have to pick just one to watch, it's got to be Chelsea-Liverpool on Sunday, with the £50m man Fernando Torres set to debut for the Blues against his former Liverpool teammates and manager Kenny Dalglish (pictured to the right, celebrating after scoring at Stamford Bridge to clinch the title for Liverpool in 1986).
England, Newcastle-Arsenal or Manchester City-West Brom 10am, FSC/FSP respectively: Take your pick to see whether the two teams right behind Man U in Premier League table can keep pace. Arsenal are on 49 pts, Man City on 46, while Man U are at the top with 54 (and still undefeated, which we expect them to maintain later in the day against cellar-dwellers Wolves)–so neither Arsenal nor Man City can afford to drop points.
Spain, Barcelona-Atletico Madrid 4pm GolTV: Atletico have been severely underachieving this season, especially given their South American star strikeforce of Diego Forlan and Kun Agüero. Barcelona should get a La Liga-record 16th consecutive victory in front of their home crowd, breaking the record set by Real Madrid in 1960-61 (the legendary squad that featured di Stefano and Puskas in attack, and that had won five European Cups in a row).
England, Chelsea-Liverpool 11am FSC: The main event of the weekend, following last Monday's transfer madness. Fernando Torres became the £50m man–that's how much Chelsea paid Liverpool for the Spanish striker, and now he'll play his first game for the Blues against his former side. Liverpool used all that money plus a bit more to replace Torres with an odd couple of effective, exciting and infamous strikers: Luis Suarez (£23m) and Andy Carroll (£35m!).
England, Wolves-Liverpool 7:30 a.m. ESPN2: This exact sort of fixture continues to bedevil Liverpool. Can they fix a two-year problem visiting the grounds of England's lesser lights? If not, will Daiglish snap?
England, Aston Villa-Manchester City 12:30 p.m. FSC: Darren Bent's debut for the Villans as they begin their campaign to avoid the drop. Gotta believe Kompany will have his hands full paired with the useless Lescott if Kolo Toure not back from injury. Can Dzeko grab his first or even play nearly as well as last time out? Who will Manciin rest after the FACup replay in mid-week?
Italy, AC Milan-Cesena 2:30 p.m. FSC: it should (might?) be interesting to see how Italian teams approach being near relegation. We are all familiar with the English "Route One", but how Cesena approach travelling to the leaders.
NFL – NFC Championship, Chicago Bears-Green Bay Packers 3pm: For only the 2nd time, we expand our listings to include an contest of the "other" football. Why this one? Because CultFootball's prehistory can be traced back to when we were (a variety of) the Monsters of the Midway.
We've been pretty regular about putting up a "what to watch this weekend" post Friday of every week. Given all the good midweek fixtures (especially with the Champions League knockout matches starting in about a month), we're going to add a similar weekly feature that will go up Monday or Tuesday.
So here's your viewing guide for this week, today thru Thursday. A handful of good matchups–two FA Cup replays involving two Premier League heavyweights hosting Championship League sides fighting above their weight; two Copa del Rey matches, one involving our new must-see Spanish team, the other a Derbi Madrileño; and a Coppa Italia match, also a capital city derby–known, in fact, as Derby della Capitale.
While most of America will no doubt be focused on the American version of football this weekend, there are plenty of futbol matches for you to watch instead. Here are a bunch of selections; one each from the German Bundesliga, the Italian Serie A, and the Spanish La Liga; a handful from the English Premier League; and an international Copa Centroamerica match, broadcast live from Panama City.
2:30pm, ESPN Deportes & ESPN3.com: Bayer Leverkusen v Dortmund #1 vs #3 in the Bundesliga table. See a detailed match preview here.
7:00pm, GolTV – Costa Rica v Honduras: We choose this Copa Centroamericana matchup since a few members of the CultFootball team will soon be travelling to Costa Rica, and hence should start getting familiar with Costa Rican football. Also a chance for all you fans of the USMNT to scout out their CONCACAF WC qualifying competition.
10:00am, FSC & Fox Deportes – Manchester City v Wolves: Man City's latest (& last?) big money signing, Bosnian striker Edin Dzeko, is set to get his English debut after being brought in from German club Wolfsburg for a mere £27 million. Mancini's Man City has been much-criticized this season for their "negative" tactics–will Dzeko somehow make them an attacking squad? Mancini said this past week he may on occasion use all five of his strikers at once (Tevez, Balotelli, Silva, Johnson, and now Dzeko; Adebayor is quite out of favor, and apparently on his way out of Manchester–maybe to Madrid!). Although Balotelli is hurt, this match against Wolves could be a chance to finally entertain the home crowd.
12:00pm, FSP, foxsoccer.tv & ESPN3.com – Napoli v Fiorentina: The Neapolitans are 2nd in Serie A, a mere four points behind AC Milan. Could this be the year of the club's 3rd Scudetto–and the first outside of the near-mythical Maradona era? Napoli's standout striker is Edinson Cavani. He was somewhat overshadowed in the World Cup by his teammates Diego Forlan and Luis Suarez, but he's come into his own this season in Italy–he's tied for the Serie A scoring lead with 13 goals, including a hat-trick last weekend against Juventus–including un scorpione.
12:30pm, Fox Deportes & FSC – West Ham v Arsenal: Which Arsenal team will show up? The one that beat Chelsea 3-1 a few weeks ago–or the one that lost to Ipswich Town on Wednesday? You'll find out only by tuning in.
9:00am, FSC – Liverpool v Everton: A Merseyside derby is a match to watch under any circumstances–but this weekend especially so. King Kenny back at Anfield, managing his club after two decades away, against their crosstown rivals–with whom their tied on points in the table, and whom they lost to 2-0 back in October. American John Henry will also be in attendance; although that's not really a reason to watch, the camera will probably find him for reaction shots.


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Each of Monica Rich Kosann's image cases are inspired by vintage accessory pieces from the past that once served a variety of purposes in everyday life. Monica saw in these shapes a new generation of possibilities: modern day image cases of the finest materials that hold something precious to all of us- the images of our friends, family, and those we love. Monica designed these image cases to become treasured family heirlooms.


Anger is a natural emotion, all humans express it, either silently or verbally. Anger is a messenger; it tells you where your beliefs are not working and where your next steps are in our journey home to God. A spiritual approach to anger includes the awareness of where your anger starts within you and a recovery process of Self-Forgiveness.


El opositor venezolano ingresó por tierra a través del Puente Internacional Simón Bolívar, de Villa del Rosario, Cúcuta y se espera que en breve parta rumbo a Europa.
Vestido con camisa clara y chaqueta oscura, Ledezma aseguró por su parte que burló el arresto sin consultarle a su "esposa e hijas" y no dio pistas claras sobre sus próximos pasos.
El dirigente opositor, Antonio Ledezma, huyó a Colombia desde Venezuela, donde permanecía en arresto domiciliario, en Caracas.
Ledezma, de 62 años, tras su detención, estuvo preso en el penal militar de Ramo Verde, en el estado Miranda, vecino a Caracas, y a los dos meses fue trasladado a su domicilio por motivos de salud.
En breves declaraciones a la prensa en la capital colombiana, Ledezma ratificó sus observaciones a ese proceso y reclamó al gobernante venezolano que libere "de inmediato" a los presos políticos si quiere un diálogo con la oposición.
There are 1,820 adults with wealth of over $50 million (Rs325 crore), while 760 have more than $100 million (Rs650 crore). The rise in global wealth reflected widespread gains in equity markets and similar rises in non-financial assets.
BidaskClub lowered Chevron Corporation from a "sell" rating to a "strong sell" rating in a report on Monday, July 24th. Prelude Mgmt Limited Liability Corporation stated it has 0.01% of its portfolio in Williams Companies Inc (NYSE:WMB).
"Esa llamada y esa palabra no son una solidaridad con la oposición, son una solidaridad con la democracia venezolana", dijo Ledezma al canal NTN 24, donde apareció con camisa clara y una bandera venezolana colgada al hombro.
Dijo además que Ledezma hizo su correspondiente trámite migratorio ante las autoridades colombianas.
Recognition for recent economic reforms in India & 5000 year track record of no default. This is unedited, unformatted feed from the Press Trust of India wire.
If you are reading this story on another domain, it was stolen and reposted in violation of United States & global copyright law. Commonwealth of Pennsylvania Public School Empls Retrmt SYS raised its position in Henry Schein by 0.3% in the second quarter.
But on Friday, a meal at the Methuen restaurant took on a special meaning for the now blended and bigger Lawrence family. The adoption of 40 infants, children and teens were finalized at Miami Children's Museum as part of the celebration.
Defence minister Niramala Sitharaman addressing a press conference on the Rafale deal. It was not financially prudent to negotiate ToT for just 36 fighters, she said.
In the interview, Eisenkot called Iran "the biggest threat to the region" and said Saudi Arabia was in "complete agreement". We will not intervene in the fighting in Syria, unless we see an attempt to harm our Druze brothers.
It was created using data compiled from satellites orbiting the Earth and it shows how life on our planet has changed. Ivona Cetenic joined FOX10 News for an interview Friday morning to tell us more about it.
November 3 investment analysts at SunTrust Banks maintained a company rating of "Buy" with a current price target of $210.00. Finally, Partnervest Advisory Services LLC grew its stake in Alibaba Group Holding Limited by 1.8% in the second quarter.
He described it as a dissociative episode: He woke up from a nap, and "it just felt like I was on the outside looking in at a conversation".
He said assistance could also be sought from the Rangers and Frontier Constabulary to disperse the protesters . However, Justice Siddiqui said that the application will only be heard if the parties ended their sit-in.


I've Hustled During Dozens of Races… But on Sunday, I Hustled Up The Hancock for the Very First Time! | Keep It Up, David!
With 100 stories, the Hancock is the 8th tallest building in the US. When it was finished in 1969, it was the second-tallest building in the world, after the Empire State Building.
Hustle Up The Hancock is the annual stair race here. This was the 20th year. It attracts over 4,000 athletes every year, and is a fundraiser for the Respiratory Health Association, bringing in over a million smackers. Whoa.
This race has been on my radar for a couple years, but two things have prevented me from coming in the past: scheduling conflicts, and the fact that it's so popular it sells out, and quickly! This year it all came together, and I've been excited to tackle this landmark, so I can add it to my list of iconic structures I've raced in, alongside Willis Tower, One World Trade Center, the Space Needle, and the Stratosphere.
While the building has 100 stories, the race is only to the the 94th floor, home to the 360 Chicago observation deck. Only – ha! 94 stories is a lot!
I was scheduled to start at 11:45am, and that was fantastic news. I had raced up 217 stories in Minneapolis just the day before, and then flown to Chicago, so I would be able to get a good night's sleep without having to get up before dawn to make it to a 7am start time.
Hustle Up The Hancock is a well-oiled machine. They distribute lots of information in advance so you know where to go and how things will work, because the crowds on race day are so large that it can make finding your way around confusing.
My 11:45 wave consisted of a couple hundred people, and I positioned myself well, so when they opened the line, I ended up being first. That was strategic on my part. If there was any gap between my wave and the prior wave, than the stairwell would be a little less crowded, and that was something I could take advantage of as I climbed.
When I entered the line, I passed a sign saying to expect a 30-minute wait, because the line snaked around the basement floor, then went up to the street level lobby, then down another hall, around the corner, and over to the elevator bank. It turns out there was a huge gap, so much so that a race organizer frantically ushered us straight to the starting line. My 30-minute wait ended up being about five minutes. I was caught off guard by this, and let a couple others go before me, so I had a few seconds to adjust my earbuds and gloves and prep my heart rate monitor and watch.
And then…. it was go time. I had been worried that I'd be achy and sore from Saturday's hour-long climbing fiesta, but I was surprisingly limber and not sore, and I started the 94-story climb feeling really good. I quickly passed the three people that I let start before me, and then had the stairwell all to myself for the next 15 stories.
That's when I started catching up to the slowest people in the wave before me, and passing them. This was my first race in a long time where I wasn't in a competitive heat, and I'm not gonna lie – passing people provides a mental boost that helps fuel me to keep going.
When I started slowing down, around the 35th floor or so, when the fatigue from Saturday's race really set in, it was seeing these racers that kept me going. I thought about my own journey, about how fear of failure had stagnated me at 402 pounds, and how scared I was to take the first steps towards building a healthier life.
And here I was, seven years later, 160 pounds lighter, and a veteran in a sport so utterly, back-breakingly difficult that many people I explain it to can't believe it's real. I've been those people I passed in the stairwell. I've walked in their shoes. Except I haven't… because they're much braver than I was at that weight.
So I kept climbing. I kept climbing because my first steps ultimately led me here, led me to the belly of this American landmark, led me to all sorts of amazing places I never could have predicted, and the only way I knew how to honor that journey was to not give up, never give up, keep climbing, keep pushing until I had nothing more to give, until I left every last watt of energy from my body in that stairwell.
I kept climbing for ME, because I'm worth all the hard work, the devotion, the sacrifices I've made to get and stay healthy. And I climbed for YOU, to show you that the fears, self-doubts and reservations that we share aren't permanent. They don't need to be anchors. You may not end up becoming a tower runner, but taking those first steps can led you to amazing places, even if you don't know yet where they are.
After 40-something repetitive floors, the stairwell changed. The floors got shorter – from 20 steps per floor to 15. This was a welcome change for a tired stair climber, because the floor numbers flew by faster. To be honest, much of this race is a blur, even though I remember my body being ablaze with fatigue, and my legs feeling heavier after every flight.
I remember thinking I could muster a sprint up the final five floors, so I tried turning up the juice at the 89th floor. Then, the 90th floor ended up being twice as tall as the ones that preceded it, and my sprint dissipated in a cloud of complete weariness and sweat.
I reclaimed my sprint as I turned on the 93rd floor landing. There, a few steps in front of me, was another climber, and I decided in that instant that I needed to pass him. I flew up the final two flights, passing the guy four steps from the top. I blasted across the finish line, and staggered around until I found a place to sit down.
And then it hit me. It all hit me. I was slammed with so many overwhelming thoughts, concurrently, that I broke down. I just climbed 311 floors in one weekend. I'm 94 stories above the sidewalk, and MY FEET brought me here. I got here in 19 minutes and 22 seconds – much faster that I ever could have imagined. But most of all, I'm here, in this moment, right now, because I'm strong, I work hard, and I did it. The tears mixed with the sweat; my body shuddered from emotion and twitched with pain.
And then I looked up, and saw the view. Man, the view. It was a crystal clear day, and from that height, beyond the forest of skyscrapers, you could see the curvature of the earth.
I stayed on the observation deck for nearly an hour, soaking up the experience, and promising myself not to forget. Not to forget what I did this morning, what I've done with my life, how I've taken control of my health. I left that John Hancock Center feeling as strong and unwavering as the building I had just climbed.
A huge thank you to Bowflex, my sponsor for this race. Their products help me train, and they've proven to be invaluable, and means so much to have this incredible company in my corner.
Another thank you goes to my friend Anne, who made a very generous donation to the Respiratory Health Association on my behalf. You're the best, Anne!
This entry was posted on Monday, February 27th, 2017 at 10:49 pm and is filed under Uncategorized.	You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
8 Responses to I've Hustled During Dozens of Races… But on Sunday, I Hustled Up The Hancock for the Very First Time!
Wow! Great race recap David and so inspiring! Congratulations and Keep It Up David!
Keep it up Amy! Hope the drive went great and gracias.
Your father stands with pride and in awe of your accomplishments, David ! Well done!
I think this is my favorite write up of yours ever! Or maybe it's just because I read it while on the step mill training for the vertical mile.
you are awesome dear friend!
Thanks for these re-caps, David! Amazing back-to-back ELITE performances by you! Very impressive accomplishments! So happy for you! Glad you stayed on the deck for an hour to soak it in!
Thank you George! Hope all your stairs are going well.