A re-examination of precipitation activity in the subtropics and the mid-latitudes based on satellite-derived data
A re-examination of precipitation activity in the subtropics and the mid-latitudes based on satellite-derived data
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DOI：
10.2151/jmsj.80.1261
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发表时间：
2002-10
影响因子：
3.1
通讯作者：
Yasu-masa Kodama;Atsushi Tamaoki
中科院分区：
文献类型：
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作者：
Yasu-masa Kodama;Atsushi Tamaoki
利用新的气候降水数据集：GPCP雨量计-卫星组合数据和TRMM- pr观测衍生的TRMM三级数据，研究了亚热带和中纬度地区的大尺度降水活动及其季节变化。在本研究中，我们发现在亚热带和中纬度之间存在显著的大尺度降水带，称为亚热带中纬度降水带（smpz）。smpz的大部分存在于海洋之上。纬向平均降水的经向变化在陆地和海洋之间存在较大差异。纬向平均降水中@40的中纬度峰值仅在海洋上空观测到，因为这40个峰值是由海洋上空的smpz形成的。中纬度峰值在秋冬两季显著增强，中纬度区域纬向延伸，降水与夏季相当。夏季，从热带季风活跃区向副热带斜向延伸。亚热带海洋的降水因此在夏季增加。在陆地上，没有发现中纬度的山峰。夏季降水增强，在亚热带和中纬度地区都是如此。中纬度地区的中纬度部分延伸到高斜压波活动所定义的风暴路径附近。然而，在秋冬季节，许多区域从风暴路径转移到低纬度地区。夏季，副热带部分斜压波活动较弱，以辐合和锋面区为特征，斜压性较弱。PR观测到的降水垂直结构表明，深（浅）层降水和对流降水对夏季（秋季和冬季）中高海拔区域的活跃降水有很大贡献。讨论了秋冬两季浅层降水与中压区偏离风暴路径的可能关系。
Large-scale precipitation activity in the subtropics and the mid-latitudes, in addition to seasonal variation, were studied using new climatological precipitation datasets: GPCP rain gauge-satellite combined data, and TRMM level-3 data derived from TRMM-PR observations. We found significant large-scale precipitation zones extending between the subtropics and the midlatitudes, referred to as SMPZs (Subtropical Mid-latitude Precipitation Zones) in this study. Most portions of the SMPZs existed over the oceans. Meridional variation of zonal averaged precipitation was quite different between land and the oceans. Mid-latitude peaks at @40 in zonal averaged precipitation were observed only over the oceans, because the SMPZs over the ocean formed the 40 peaks. The midlatitude peaks significantly intensified in the fall and winter when the SMPZs zonally extended in the mid-latitudes and kept precipitation as substantial as in summer. In summer, the SMPZs extended diagonally across the subtropics from the active tropical monsoon rainfall areas. Precipitation over the subtropical oceans thus increased in summer. Over land, mid-latitude peaks were not found. Precipitation intensified in summer, both in the subtropics and in the mid-latitudes. The mid-latitude portions of the SMPZs extended near the storm tracks defined by high baroclinic wave activity. However, many portions of the SMPZs shifted to the lower latitudes from the storm tracks in fall and winter. In summer, baroclinic wave activity was weak for the subtropical portions of the SMPZs, which were characterized by convergence and frontal zones with weak baroclinicity. Vertical structure of precipitation observed by PR suggested that deep (shallow) stratiform and convective precipitation largely contributed to the active rainfall along the SMPZs in summer (fall and winter). A possible relationship between the shallow precipitation and the displacement of the SMPZs from the storm tracks in fall and winter was discussed.