Radiosonde stratospheric temperatures at Dumont d'Urville (Antarctica): trends and link with polar stratospheric clouds

摘要

Temperature profiles measurements are performed daily (00:00 UT) in Dumontd'Urville (66°40' S, 140°01' E) by Météo-France, usingstandard radiosondes, since the International Geophysical Year in 1957. Yet,due to a 16 years data gap between 1963 and 1978, the entire dataset is onlyused for a qualitative overview. Only the most recent series, between 1979and 2008, is used to investigate the inter-annual stratospheric temperaturesvariability. Over Dumont d'Urville, at the edge of the vortex, the annualmean temperature cooling of about 1 K/decade at 20 km is the result of thecooling trends between 0.5 and 1.4 K/decade, in summer and autumn and awarming of about 1.1 K/decade in spring. These values are consistent withvalues obtained using data from inner vortex stations, but with smalleramplitude. No statistically significant trend is detected in winter. Wepropose here the first attempt to link stratospheric temperature trends toPolar Stratospheric Cloud (PSC) trends in Antarctica based on the onlycontinuous 20 years database of PSC lidar detection. Despite the absence ofmean temperature trend during winter, the occurrence of temperatures belowthe NAT threshold between 1989 and 2008 reveals a significant trend of about+6%/decade. The PSCs occurrences frequency exhibits a concomitant trendof about +3%/decade, although not statistically significant. Yet, thisis consistent with results obtained in the Northern Hemisphere. Such apossible positive trend in PSC occurrence has to be further explored to beconfirmed or invalidated. If confirmed, this PSC trend is likely to havestrong impacts, both on ozone recovery and climate evolution in Antarctica.The study also reveals the importance of trends on extreme temperatures, andnot only on mean temperatures.