The vertical structure of precipitation at two stations in East Antarctica derived from micro rain radars

Abstract

Abstract. Precipitation over Antarctica is the main term in the surface mass\nbalance of the Antarctic ice sheet, which is crucial for the future evolution\nof the sea level worldwide. Precipitation, however, remains poorly documented\nand understood mainly because of a lack of observations in this extreme\nenvironment. Two observatories dedicated to precipitation have been set up at\nthe Belgian station Princess Elisabeth (PE) and at the French station Dumont\nd Urville (DDU) in East Antarctica. Among other instruments, both sites\nhave a vertically pointing micro rain radar (MRR) working at the K\xa0band.\nMeasurements have been continuously collected at DDU since the austral summer\nof\n2015–2016, while they have been collected mostly during summer seasons at PE\nsince 2010, with a full year of observation during 2012. In this study, the\nstatistics of the vertical profiles of reflectivity, vertical velocity, and\nspectral width are analyzed for all seasons. Vertical profiles were separated\ninto surface precipitation and virga to evaluate the impact of virga on the\nstructure of the vertical profiles. The climatology of the study area plays\nan important role in the structure of the precipitation: warmer and moister\natmospheric conditions at DDU favor the occurrence of more intense\nprecipitation compared with PE, with a difference of 8\u2009dBZ between both\nstations. The strong katabatic winds blowing at DDU induce a decrease in\nreflectivity close to the ground due to the sublimation of the snowfall\nparticles. The vertical profiles of precipitation velocity show significant\ndifferences between the two stations. In general, at DDU the vertical\nvelocity increases as the height decreases, while at PE the vertical velocity\ndecreases as the height decreases. These features of the vertical profiles of\nreflectivity and vertical velocity could be explained by the more frequent\noccurrence of aggregation and riming at DDU compared to PE because of the\nlower temperature and relative humidity at the latter, located further in the\ninterior. Robust and reliable statistics about the vertical profile of\nprecipitation in Antarctica, as derived from MRRs for instance,\nare necessary and valuable for the evaluation of precipitation estimates\nderived from satellite measurements and from numerical atmospheric models.