An Assessment of Precipitation Changes over Antarctica and the Southern Ocean since 1989 in Contemporary Global Reanalyses
An Assessment of Precipitation Changes over Antarctica and the Southern Ocean since 1989 in Contemporary Global Reanalyses
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DOI：
10.1175/2011jcli4074.1
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发表时间：
2011-08-01
影响因子：
4.9
通讯作者：
Monaghan, Andrew J.
中科院分区：
文献类型：
--
作者：
Bromwich, David H.;Nicolas, Julien P.;Monaghan, Andrew J.
本研究评估了 1989 年至 2009 年期间五次全球再分析中南极表面质量平衡（近似为降水量减去蒸发量 (P - E)）和南大洋降水量的时间变化。数据集包括 NCEP/U.S.能源部 (DOE) 大气模式比对项目 2 再分析 (NCEP-2)、日本气象厅 (JMA) 25 年再分析 (JRA-25)、ECMWF 中期再分析 (ERA-Interim)、NASA 现代时代回顾性研究和应用分析 (MERRA) 以及气候预报系统再分析 (CFSR)。众所周知，重新分析很容易出现由观测系统变化引起的虚假趋势和不均匀性，特别是在数据稀疏的南部高纬度地区。在研究期间，用于数据同化的卫星观测数量急剧增加。NCEP-2、JRA-25 和 MERRA 中南极洲平均 P-E 和南大洋平均降水量的大正趋势和统计显着趋势在很大程度上是虚假的。这些伪影的来源因重新分析而异。值得注意的是，20 世纪 90 年代末 MERRA 的降水量猛增，恰逢高级微波探测装置 (AMSU) 开始同化辐射。 ERA-Interim 和 CFSR 没有表现出任何显着趋势。然而，ERA-Interim 中受降雨影响的辐射同化的潜在影响以及南极洲 CFSR 压力场的不均匀性使人们对这两个数据集的可靠性产生了一些怀疑。作者得出的结论是，ERA-Interim 可能提供了 1989-2009 年期间南部高纬度地区降水变化的最真实描述。再分析中南极P-E的趋势范围相当于21年来海平面的1毫米，这凸显了再分析模拟中仍需要改进，以更好地评估南极洲对海平面上升的贡献。最后，这项工作主张继续谨慎使用再分析数据集进行气候变化评估。
This study evaluates the temporal variability of the Antarctic surface mass balance, approximated as precipitation minus evaporation (P - E), and Southern Ocean precipitation in five global reanalyses during 1989-2009. The datasets consist of the NCEP/U.S. Department of Energy (DOE) Atmospheric Model Intercomparison Project 2 reanalysis (NCEP-2), the Japan Meteorological Agency (JMA) 25-year Reanalysis (JRA-25), ECMWF Interim Re-Analysis (ERA-Interim), NASA Modern Era Retrospective-Analysis for Research and Application (MERRA), and the Climate Forecast System Reanalysis (CFSR). Reanalyses are known to be prone to spurious trends and inhomogeneities caused by changes in the observing system, especially in the data-sparse high southern latitudes. The period of study has seen a dramatic increase in the amount of satellite observations used for data assimilation.The large positive and statistically significant trends in mean Antarctic P - E and mean Southern Ocean precipitation in NCEP-2, JRA-25, and MERRA are found to be largely spurious. The origin of these artifacts varies between reanalyses. Notably, a precipitation jump in MERRA in the late 1990s coincides with the start of the assimilation of radiances from the Advanced Microwave Sounding Unit (AMSU). ERA-Interim and CFSR do not exhibit any significant trends. However, the potential impact of the assimilation of rain-affected radiances in ERA-Interim and inhomogeneities in CFSR pressure fields over Antarctica cast some doubt on the reliability of these two datasets.The authors conclude that ERA-Interim likely offers the most realistic depiction of precipitation changes in high southern latitudes during 1989-2009. The range of the trends in Antarctic P - E among the reanalyses is equivalent to 1 mm of sea level over 21 years, which highlights the improvements still needed in reanalysis simulations to better assess the contribution of Antarctica to sea level rise. Finally, this work argues for continuing cautious use of reanalysis datasets for climate change assessment.