Cloud and precipitation properties from ground-based remote-sensing instruments in East Antarctica

摘要

A new comprehensive cloud–precipitation–meteorological observatory has beenestablished at Princess Elisabeth base, located in the escarpment zone ofDronning Maud Land (DML), East Antarctica. The observatory consists of a set ofground-based remote-sensing instruments (ceilometer, infrared pyrometer andvertically profiling precipitation radar) combined with automatic weatherstation measurements of near-surface meteorology, radiative fluxes, and snowheight. In this paper, the observatory is presented and the potential forstudying the evolution of clouds and precipitating systems is illustrated bycase studies. It is shown that the synergetic use of the set of instrumentsallows for distinguishing ice, liquid-containing clouds and precipitating clouds,including some information on their vertical extent. In addition, wind-drivenblowing snow events can be distinguished from deeper precipitating systems.Cloud properties largely affect the surface radiative fluxes, withliquid-containing clouds dominating the radiative impact. A statisticalanalysis of all measurements (in total 14 months mainly during summer–beginning of winter)indicates that these liquid-containing clouds occur during as much as 20% ofthe cloudy periods. The cloud occurrence shows a strong bimodal distributionwith clear-sky conditions 51% of the time and complete overcast conditions35% of the time. Snowfall occurred during 17% of the cloudy periods with apredominance of light precipitation and only rare events with snowfall>1 mm h?1 water equivalent (w.e.). Three of such intensesnowfall events occurred during 2011 contributing to anomalously large annualsurface mass balance (SMB). Large accumulation events(>10 mm w.e. day?1) during the radar-measurement period of 26months were always associated with snowfall, but at the same time othersnowfall events did not always lead to accumulation. The multiyear deploymentof a precipitation radar in Antarctica allows for assessing the contribution ofthe snowfall to the local SMB and comparing it to the other SMB components.During 2012, snowfall rate was 110 ± 20 mm w.e. yr?1, fromwhich surface and drifting snow sublimation removed together 23%. Given themeasured yearly SMB of 52 ± 3 mm w.e., the residual term of33 ± 21 mm w.e. yr?1 was attributed to the wind-driven snowerosion. In general, this promising set of robust instrumentation allows forimproved insight into cloud and precipitation processes in Antarctica and canbe easily deployed at other Antarctic stations.