How does the spaceborne radar blind zone affect derived surface snowfall statistics in polar regions?
How does the spaceborne radar blind zone affect derived surface snowfall statistics in polar regions?
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DOI：
10.1002/2014jd022079
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发表时间：
2014-12
期刊：
影响因子：
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通讯作者：
M. Maahn;C. Burgard;S. Crewell;I. Gorodetskaya;S. Kneifel;S. Lhermitte;K. Van Tricht;N. P. M. Lipzig
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文献类型：
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作者：
M. Maahn;C. Burgard;S. Crewell;I. Gorodetskaya;S. Kneifel;S. Lhermitte;K. Van Tricht;N. P. M. Lipzig
全球降雪量统计数据目前只能从CloudSat卫星获得。但是CloudSat无法提供所谓盲区内的云和降水观测，这是由CloudSat雷达的地面杂波污染造成的，覆盖了陆地/冰面以上的最后1200米。在这项研究中，CloudSat盲区对极地地区降雪量统计数据的影响通过分析三个12个月的数据集进行了研究，这些数据集是由地面微雨雷达（MRR）在南极洲东部的比利时伊丽莎白公主站和挪威斯瓦尔巴群岛的Ny‐ lewesund和Longyearbyen记录的。MRR雷达反射率廓线的频率分布的垂直变化，观测到的雪事件的数量的变化，和总降水的影响方面进行了研究。结果表明，盲区导致反射率被低估达1dB，事件数被改变±5%，降水量被低估9 ~ 11个百分点。除了研究1200 m的盲区外，还分析了600 m的缩小盲区的影响。这一分析将有助于评估未来具有较小盲区的任务。减少盲区导致平均反射率的改善，但并没有改善事件数和降水量的偏差的代表性。
Global statistics of snowfall are currently only available from the CloudSat satellite. But CloudSat cannot provide observations of clouds and precipitation within the so‐called blind zone, which is caused by ground‐clutter contamination of the CloudSat radar and covers the last 1200 m above land/ice surface. In this study, the impact of the blind zone of CloudSat on derived snowfall statistics in polar regions is investigated by analyzing three 12 month data sets recorded by ground‐based Micro Rain Radar (MRR) at the Belgian Princess Elisabeth station in East Antarctica and at Ny‐Ålesund and Longyearbyen in Svalbard, Norway. MRR radar reflectivity profiles are investigated in respect to vertical variability in the frequency distribution, changes in the number of observed snow events, and impacts on total precipitation. Results show that the blind zone leads to reflectivity being underestimated by up to 1 dB, the number of events being altered by ±5% and the precipitation amount being underestimated by 9 to 11 percentage points. Besides investigating a blind zone of 1200 m, the impacts of a reduced blind zone of 600 m are also analyzed. This analysis will help in assessing future missions with a smaller blind zone. The reduced blind zone leads to improved representation of mean reflectivity but does not improve the bias in event numbers and precipitation amount.