Lidar temperature measurements during the SOLVE campaign and the absence of polar stratospheric clouds from regions of very cold air

Abstract

NASA Goddard Space Flight Center's Airborne Raman Ozone, Temperature, and Aerosol Lidar (AROTEL) measured extremely cold temperatures during all three deployments (1–16 December 1999, 14–29 January 2000, and 27 February to 15 March 2000) of the SAGE III Ozone Loss and Validation Experiment (SOLVE). Temperatures were significantly below values observed in previous years with large regions regularly below 191 K and frequent temperature retrievals yielding values at or below 187 K. Temperatures well below the saturation point of type I polar stratospheric clouds (PSCs) were regularly encountered, but their presence was not well correlated with PSC observations made by NASA Langley Research Center's aerosol lidar colocated with AROTEL. Temperature measurements by meteorological sondes launched within areas traversed by the DC‐8 showed minimum temperatures consistent in time and vertical extent with those derived from AROTEL data. Calculations to establish whether PSCs could exist at measured AROTEL temperatures and observed mixing ratios of nitric acid and water vapor showed large areas favorable to PSC formation but that were lacking PSCs. The flight on 12 December 1999 encountered large regions having temperatures up to 10 K below the NAT saturation temperature but only small, localized regions that might be identified as PSCs.