Vertical distribution of water vapor in the Arctic stratosphere in January-February 2004 from data of the LAUTLOS field campaign

The results of measurements of water-vapor vertical profiles in the upper troposphere and lower stratosphere on board a meteorological sounding balloon with the use of a FLASH-B optical fluorescent hygrometer are presented. These results were obtained during the LAUTLOS-WAVVAP international experiment on the comparison of balloon hygrometers, which was carried out in January-February 2004 in northern Finland. Humidity values are determined inside, outside, and at the boundary of the circumpolar stratospheric cyclone. It is shown that, at a height of 20 km, the difference between the mixing ratios of water vapor outside and inside the cyclone can attain 1 ppm and increases with height. It is inferred that the layered structure of the vertical humidity profile at the stratospheric-cyclone boundary is caused by inhomogeneous advection of air masses. The humidity-profile layering is in good agreement with the layering of the potential-vorticity profile, which points to the dynamic nature of these layers. It is shown that decreased values of the water-vapor content observed in the polar stratosphere are not always controlled by dehydration processes associated with the formation and sedimentation of particles of polar stratospheric clouds.