Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 4 2004 10.5194/acpd-4-4581-2004 http://www.atmos-chem-phys-discuss.net/4/4581/2004/ http://www.atmos-chem-phys-discuss.net/4/4581/2004/acpd-4-4581-2004.html http://www.atmos-chem-phys-discuss.net/4/4581/2004/acpd-4-4581-2004.pdf 4581 4609 2004-08-20 Influence of mountain waves and NAT nucleation mechanisms on Polar Stratospheric Cloud formation at local and synoptic scales during the 1999&ndash;2000 Arctic winter S. H. Svendsen shs@dmi.dk N. Larsen B. Knudsen S. D. Eckermann E. V. Browell Danish Meteorological Institute, Copenhagen, Denmark Naval Research Laboratory, Washington DC, USA NASA Langley Research Center, Hampton, Virginia, USA A scheme for introducing mountain wave-induced temperature pertubations in a microphysical PSC model has been developed. A data set of temperature fluctuations attributable to mountain waves as computed by the Mountain Wave Forecast Model (MWFM-2) has been used for the study. The PSC model has variable microphysics, enabling different nucleation mechanisms for nitric acid trihydrate, NAT, to be employed. In particular, the difference between the formation of NAT and ice particles in a scenario where NAT formation is not dependent on preexisting ice particles, allowing NAT to form at temperatures above the ice frost point, <i>T<sub>ice</sub></i>, and a scenario, where NAT nucleation is dependent on preexisting ice particles, is examined. The performance of the microphysical model in the different microphysical scenarios and a number of temperature scenarios with and without the influence of mountain waves is tested through comparisons with lidar measurements of PSCs made from the NASA DC-8 on 23 and 25 January during the SOLVE/THESEO 2000 campaign in the 1999&ndash;2000 winter and the effect of mountain waves on local PSC production is evaluated in the different microphysical scenarios. Mountain wave-induced temperature fluctuations are introduced in vortex-covering model runs, extending the full 1999&ndash;2000 winter season, and the effect of mountain waves on large-scale PSC production is estimated in the different microphysical scenarios.