The GRUAN station FMI-ARC in Sodankylä Finland organized an atmospheric sounding campaign in early 2010, which included participants from several countries. The first phase of the campaign was focussing on radiosonde inter-comparisons that were carried out in January-February 2010. Different commercial and research grade in situ instruments were launched with a focus on the comparison of humidity and temperature measurements in the troposphere and stratosphere.
The campaign included the most accurate light-weight balloon borne water vapor instruments such as FLASH-B (Lyman- alpha fluorescence hygrometer) and the Cryogenic Frostpoint Hygrometer (CFH). The new reference radiosonde by Vaisala RR01 was flown in the same payload with the cryogenic frost point hygrometer and the fluorescence hygrometer. The remote sensing instruments participating in the campaign included the new microwave radiometer for water vapor measurements MIAWARA-C developed by the University of Bern. Partners from Germany (DWD), Switzerland (ETHZ), Russia (CAO) and Finland (FMI, Vaisala) were participating in the in situ measurements.
Stratospheric measurements were made under very low temperatures in the Arctic vortex in January 2010. Thus polar stratospheric clouds were frequently measured by aerosol backscatter sondes during the campaign. The simultaneous measurements of water vapor indicated dehydration in the vortex in January 2010 related to the formation of the polar stratospheric clouds.