Abstract
Abstract. Climate models predict Antarctic precipitation to increase during the 21st century, but their present day Antarctic precipitation differs. A model-independent climatology of the Antarctic precipitation characteristics, such as snowfall rates and frequency, is needed to assess the models, but it is not yet available. Satellite observations of precipitation by active sensors has been possible in the polar regions since the launch of CloudSat in 2006. Here, we use two CloudSat products to generate the first multi-year, model-independent climatology of Antarctic precipitation. The first product is used to determine the frequency and the phase of precipitation, while the second product is used to assess the snowfall rate. The mean snowfall rate from August 2006 to April 2011 is 171 mm year−1 over the Antarctic ice sheet, north of 82° S. While uncertainties on individual precipitation retrievals from CloudSat data are potentially large, the mean uncertainty should be much smaller, but cannot be easily estimated. There are no in situ measurements of Antarctic precipitation to directly assess the new climatology. However, distributions of both precipitation occurrences and rates generally agree with the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim data set, the production of which is constrained by various in situ and satellite observations, but does not use any data from CloudSat. The new data set thus offers unprecedented capability to quantitatively assess Antarctic precipitation statistics and rates in climate models.
Highlights
Evaluating Antarctic snow accumulation, the sum of precipitation, sublimation/evaporation, meltwater run-off, and blowing snow (Eisen et al, 2008), is a major challenge with relevance to sea level rise
Distributions of both precipitation occurrences and rates generally agree with the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim data set, the production of which is constrained by various in situ and satellite observations, but does not use any data from CloudSat
While no significant change in the total Antarctic snow accumulation has been found in ice cores and reanalysis products over the last 50 years (Monaghan et al, 2006a; Frezzotti et al, 2013), future changes are likely to occur, with global consequences: a projected 25 % increase in accumulation over the 21st century would result in a drop of approximately 160 mm per century in global sea level (Gregory and Huybrechts, 2006)
Summary
Evaluating Antarctic snow accumulation, the sum of precipitation, sublimation/evaporation, meltwater run-off, and blowing snow (Eisen et al, 2008), is a major challenge with relevance to sea level rise. Climate models consistently predict Antarctic precipitation to increase in a warming climate (Church et al, 2013). The Antarctic precipitation rates have been evaluated from regional atmospheric models (Bromwich et al, 2004; Van de Berg et al, 2005; Monaghan et al, 2006b; Lenaerts et al, 2012). The mean solid precipitation rate over the grounded ice sheet reported by Van de Berg et al (2005) is 164 mm year−1 using the model RACMO2/ANT. That the mean precipitation rate on the grounded ice sheet varies from 145 to 203 mm year−1, depending on the reanalysis. With data available from August 2006 to April 2011, CloudSat directly observes snow precipitating through the atmosphere, rather than after it has been accumulated on the surface. We used two CloudSat products to make the first multiyear climatology of Antarctic precipitation north of 82◦ S from spaceborne observations
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