Humidity observations in the Arctic troposphere over Ny-Ålesund, Svalbard based on 14 years of radiosonde data

International audienceWater vapour is an important component in the radiative balance of the polar atmosphere. We present a study covering fourteen-years of data of tropopsheric humidity profiles measured with standard radiosondes at Ny-Ålesund (78°55' N 11°52' E) during the period from 1991 to 2005. It is well known that relative humidity measurements are less reliable at cold temperatures when measured with standard radiosondes. The data were corrected for errors and used to determine key characteristic features of the vertical and temporal RH evolution in the Arctic troposphere over Ny-Ålesund. We present frequency occurrence of ice-supersaturation layers in the troposphere, their vertical span, temperature and statistical distribution. Supersaturation with respect to ice shows a clear seasonal behaviour. In winter (October?February) it occurred in 22% of all cases and less frequently in spring (March?May 13%), and summer (June?September, 10%). The results are finally compared with findings from the SAGE II satellite instrument on subvisible clouds