Definitions of the measured values

Aerosol concentration: total number of suspended particles in volume unit of air.
Measured every 7.5 m along the optical path of lidar impulse.
The measurement is not direct: the value measured directly is the backscattered signal
and output energy of the laser for several wavelengths (laser lines).
Backscattered signal for a few wavelengths allows for the solution of the inverse lidar problem
to get the concentration and rogue shape of concentration size distribution.

Aerosol Concentration Definition Parameters:

symbol: LIDAR-AER

physical unit: m-3

range: 0 - 109

precision of measurements: 20% with support of PMS data,
50% without PMS data

Spectra of sea-water fluorescence: emitted spectra of fluorescence of sea-water
and Raman bands measured with the lidar system (1024 spectral canals). The sea surface is
illuminated with a laser beam at a chlorophyll "a" absorption band. The ratio of the
integrals of the chlorophyll "a" emission band to the Raman band allows the calculation of
a relative index of chlorophyll fluorescnce. This index, when calibrated with chlorophyll "a"
concentration values measured with the classic spectrophotometric method for some neighbouring
stations, allows practically continuing measurement of chlorophyll "a" concentration.
The concentration is a weighted average for surface water (with light transmission to
the depth at laser wavelength used as the weight).

Index of sea-surface oil fluorescence:
The index is calculated from the emitted spectra of fluorescence of sea-water
and Raman bands measured with the lidar system which are used also for
chlorophyll concentration studies.
The value of the index is a weighted average for surface water (with light transmission to
the depth at laser wavelength used as the weight).
By dividing the fluorescence spectrum into bands of the fluorescent substance and backscattered
water Raman one obtains the fluorescent coefficient of the oil (fluorescent substance). This expression mainly
depends on the oil (fluorescent substance) concentration and is independent on many
parameters as: laser power, distance from the object and sensor efficiency coefficients
which are the same for both of bands. In this way we can determine the fluorescent
coefficient of the oil which is the measure of the oil concentration.

The equipment:

Lidar System FLS-12 uses excimer laser ELI-130 to pump a dye laser DL_LIDAR
as the light source, a 280 mm telescope with a polychromator and two receiver cameras
(A and B) as the receiver. The parameters of the optical system are:

- beam divergence 5 mrad for the excimer laser and 1 mrad for the dye one

- excimer laser wavelength: 308 nm

- dye laser wavelength: tuned in range: 320-670 nm

- half-width of the dye laser impulse 0.1 nm

- impulse frequency 1-10 Hz,

- impulse duration 15 ns,

- impulse energy 70 mJ for the excimer laser and 3 mJ for the dye one.

The main part of the receiver block of the lidar system consists of a telescope of 280 mm
radius and 635 mm focus distance and working distance range of 30-2000 m.
The return signal passes through a polychromator with a spectral range of
425-800 nm. The lidar system is controlled by a PC unit which receives and
stores the distance or spectral profiles measured.