Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 4 4 2004 10.5194/acp-4-1149-2004 http://www.atmos-chem-phys.net/4/1149/2004/ http://www.atmos-chem-phys.net/4/1149/2004/acp-4-1149-2004.html http://www.atmos-chem-phys.net/4/1149/2004/acp-4-1149-2004.pdf 1149 1165 2004-07-30 Mountain wave PSC dynamics and microphysics from ground-based lidar measurements and meteorological modeling J. Reichardt A. Dörnbrack S. Reichardt P. Yang T. J. McGee Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, Maryland, USA Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR) Oberpfaffenhofen, Weßling, Germany Department of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA now at: Meteorologisches Observatorium Lindenberg, Deutscher Wetterdienst, Tauche, Germany The day-long observation of a polar stratospheric cloud (PSC) by two co-located ground-based lidars at the Swedish research facility Esrange (67.9° N, 21.1° E) on 16 January 1997 is analyzed in terms of PSC dynamics and microphysics. Mesoscale modeling is utilized to simulate the meteorological setting of the lidar measurements. Microphysical properties of the PSC particles are retrieved by comparing the measured particle depolarization ratio and the PSC-averaged lidar ratio with theoretical optical data derived for different particle shapes. In the morning, nitric acid trihydrate (NAT) particles and then increasingly coexisting liquid ternary aerosol (LTA) were detected as outflow from a mountain wave-induced ice PSC upwind Esrange. The NAT PSC is in good agreement with simulations for irregular-shaped particles with length-to-diameter ratios between 0.75 and 1.25, maximum dimensions from 0.7 to 0.9 µm, and a number density from 8 to 12 cm^-3 and the coexisting LTA droplets had diameters from 0.7 to 0.9 µm, a refractive index of 1.39 and a number density from 7 to 11 cm^-3. The total amount of condensed HNO₃ was in the range of 8–12 ppbv. The data provide further observational evidence that NAT forms via deposition nucleation on ice particles as a number of recently published papers suggest. By early afternoon the mountain-wave ice PSC expanded above the lidar site. Its optical data indicate a decrease in minimum particle size from 3 to 1.9 µm with time. Later on, following the weakening of the mountain wave, wave-induced LTA was observed only. Our study demonstrates that ground-based lidar measurements of PSCs can be comprehensively interpreted if combined with mesoscale meteorological data.