Stratospheric water vapour in the vicinity of the Arctic polar vortex

• Main Authors: M. Maturilli, F. Fierli, V. Yushkov, A. Lukyanov, S. Khaykin, A. Hauchecorne
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.592.5436; http://hal.archives-ouvertes.fr/docs/00/33/00/69/PDF/angeo-24-1511-2006.pdf

Abstract. The stratospheric water vapour mixing ratio in-side, outside, and at the edge of the polar vortex has been accurately measured by the FLASH-B Lyman-Alpha hygro-meter during the LAUTLOS campaign in Sodankylä, Fin-land, in January and February 2004. The retrieved H2O pro-files reveal a detailed view on the Arctic lower stratospheric water vapour distribution, and provide a valuable dataset for the validation of model and satellite data. Analysing the mea-surements with the semi-lagrangian advection model MI-MOSA, water vapour profiles typical for the polar vortex’ interior and exterior have been identified, and laminae in the observed profiles have been correlated to filamentary struc-tures in the potential vorticity field. Applying the validated MIMOSA transport scheme to specific humidity fields from operational ECMWF analyses, large discrepancies from the observed profiles arise. Although MIMOSA is able to repro-duce weak water vapour filaments and improves the shape of the profiles compared to operational ECMWF analyses, both models reveal a dry bias of about 1 ppmv in the lower strato-sphere above 400 K, accounting for a relative difference from the measurements in the order of 20%. The large dry bias in the analysis representation of stratospheric water vapour in the Arctic implies the need for future regular measurements of water vapour in the polar stratosphere to allow the valida-tion and improvement of climate models.