The Arctic atmospheric boundary layer (AABL) in the central
Arctic was characterized by dropsonde, lidar, ice thickness and
airborne in situ measurements during the international Polar
Airborne Measurements and Arctic Regional Climate Model
Simulation Project (PAMARCMiP) in April 2009. We discuss AABL
observations in the lowermost 500 m above (A) open water, (B)
sea ice with many open/refrozen leads (C) sea ice with few
leads, and (D) closed sea ice with a front modifying the AABL.
Above water, the AABL had near-neutral stratification and
contained a high water vapor concentration. Above sea ice, a low
AABL top, low near-surface temperatures, strong surface-based
temperature inversions and an increase of moisture with altitude
were observed. AABL properties and particle concentrations were
modified by a frontal system, allowing vertical mixing with the
free atmosphere. Above areas with many leads, the potential
temperature decreased with height in the lowest 50 m and was
nearly constant above, up to an altitu