Statistical study of polar stratospheric clouds observations by ground- and satellite based lidars and relevance for chemistry climate models

Abstract:

A statistical comparison of polar stratospheric clouds (PSCs) occurrence from 2006 to 2010 is presented, as observed from the ground based station McMurdo (Antarctica), included as a primary station in the NDACC (Network for Detection of Atmospheric Climate Change) and by the satellite borne CALIOP lidar measuring over McMurdo, in order to assess possible biases arising from different classification methods deriving from the specific geometry and sampling. Point-to-point comparison between ground based and satellite based lidar measurements is practically impossible due to the intrinsic differences in the observation geometries and the imperfect overlap of the observed areas. Therefore a statistical approach has been used to compare ground based and satellite based observations. The distribution of PSCs over Antarctica, calculated by several CCMVAL-2 and CCMI chemistry climate models has been compared with the PSC cover observed by the satellite based CALIOP lidar. The use of relatively straightforward diagnostic tools, including the temperature dependence of the PSC occurrences, evidences the merits and flaws of the different models. In particular, a significant temperature bias of most models has been observed as well as a limited ability to reproduce the longitudinal variations in PSC occurrences observed by CALIOP.