| 东亚中纬度干旱/半干旱区降水年际变化及其可能成因 |
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| 引用本文： | 王远皓,陈文,张井勇.东亚中纬度干旱/半干旱区降水年际变化及其可能成因[J].气候与环境研究,2012,17(4):444-456. |
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| 作者姓名： | 王远皓 陈文 张井勇 |
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| 作者单位： | 1. 中国科学院大气物理研究所季风系统研究中心,北京100190;中国科学院研究生院,北京 100049
2. 中国科学院大气物理研究所季风系统研究中心,北京,100190 |
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| 基金项目： | 国家重点基础研究发展规划项目2009CB421405;国家自然科学基金 41025017、40730952 |
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| 摘 要： | 基于NOAA的全球陆地降水资料(PREC/L)1948～2003年56年的月平均降水资料、NCEP/NCAR月平均再分析资料以及英国气象局哈德莱中心的海温(Sea Surface Temperature,SST)资料,并根据多年降水平均图选定了东亚中纬度干旱/半干旱区,对该区域夏季(6～8月)降水进行了经验正交分解(Empirical Orthogonal Function,EOF)。EOF第一模态呈现出全区一致的变化类型,第二模态则呈现出以100°E为界东西相反的分布类型。通过分析干旱/半干旱区以及以100°E为界的东西两部分降水异常年的环流形势和海温并加以对比,结果表明:在环流场上,对应于东亚中纬度干旱/半干旱区降水偏多年,对流层中下层环流异常在中高纬度呈现为一个东西向波列,乌拉尔山东侧为正的高度异常,贝加尔湖附近乃至以东地区为低压槽所控制;不同的是,对应于100°E以西的干旱/半干旱区夏季降水偏多年,波列有所东移,并且西太平洋副热带高压有显著北抬;而对应于100°E以东干旱/半干旱区夏季降水偏多年,环流形势异常基本与整个干旱/半干旱区降水偏多年一致,只是在里海附近有一高度负异常。在200hPa纬向风场上可以看到,当西亚副热带急流偏南加强时,对应于100°E以西的干旱/半干旱区降水偏多;而当东亚、西亚风急流都有显著北抬且加强时,对应于100°E以东干旱/半干旱区的夏季降水偏多,这可能与急流所激发的次级环流有关。进一步对SST的分析表明,海温与100°E以东或以西干旱/半干旱区降水异常的关系也不一样。当前冬、前春赤道中东太平洋都有正的海温异常,而到夏季转换为负的海温异常,且南太平洋在前冬和前春呈现显著负海温异常时,整个干旱/半干旱区夏季降水偏多;当赤道中东太平洋海温在前冬、前春有正的海温异常并一直减弱,但能维持到夏季,并且北印度洋海温也存在类似的海温异常时,100°E以西的干旱/半干旱区夏季降水偏多;而当前冬中东太平洋海温较暖但其南部海域偏冷,到了前春这些异常维持,并发展到同期为大范围弱的异常冷海温时,有利于100°E以东的干旱/半干旱区夏季降水偏多。比较的结果还揭示出,对应于干旱/半干旱区以及100°E以东干旱/半干旱区的降水异常年,海温异常分布大致是一致的;而对应于100°E以西干旱/半干旱区的降水异常年,海温异常分布及时间演变则有较大差异。
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| 关 键 词： | 干旱/半干旱区 夏季降水 西风急流 波列 海温异常 |
| 收稿时间： | 2010/12/16 0:00:00 |
| 修稿时间： | 2011/6/21 0:00:00 |
Interannual Variations of Summer Rainfall and Their Causes in the Mid-latitude Arid/Semi-Arid Areas of East Asia |
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| WANG Yuanhao,CHEN Wen and ZHANG Jingyong.Interannual Variations of Summer Rainfall and Their Causes in the Mid-latitude Arid/Semi-Arid Areas of East Asia[J].Climatic and Environmental Research,2012,17(4):444-456. |
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| Authors: | WANG Yuanhao CHEN Wen and ZHANG Jingyong |
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| Institution: | Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100190
;Graduate University, Chinese Academy of Sciences, Beijing 100049;Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100190
;;Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100190
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| Abstract: | Based on the precipitation data on land (PREC/L) from NOAA during 1948-2003 (56 years), the monthly mean NCEP/NCAR reanalysis data, and the sea surface temperature (SST) data from Meteorology Office Hadley Centre of the UK, the authors choose the arid/semi-arid areas from the climate average chart of precipitation. The regional characteristics of the mean rainfall from June to August are revealed by the empirical orthogonal function (EOF) analysis, the first EOF mode showing a consistent change in the region, while the second EOF mode showing an east-west contrast pattern. The authors divide the arid/semi-arid areas by the 100°E meridian. The circulation anomalous features associated with the three areas are then investigated through composite analyses. In the circulation field, corresponding to the more rainfall years of East Asian arid/semi-arid areas, at the lower troposphere the anomalous circulation showing a west-east wave train structure, a strong positive anomaly locates to the east of the Ural ridge of high, and a low pressure trough controls the region to the east of Lake Baikal. Differently, the wave train moves eastward and the western Pacific subtropical high moves northward and becomes stronger corresponding to the more rainfall years of the arid/semi-arid areas in the western part of 100°E. Corresponding to the more rainfall years of the arid/semi-arid areas in the eastern part of 100°E, the anomalous circulation is in essence the same as the wave train, except the negative anomalous located at the Caspian Sea. In the 200-hPa zonal wind field, when the West Asian westerly jet stream (ASWJS) axis moves southward than normal, there is more rainfall in the west part of arid/semi-arid areas. When the westerly jet stream strengthens significantly and moves northward, there is more rainfall in the east part of arid/semi-arid areas, which is related to the secondary circulation inspired by ASWJS. Further analyses on the SST shows that SST has different influences on the two regions. During preceding winter (December to next February) and preceding spring (March to May), the equatorial eastern Pacific SST anomalies are positive, while there are negative SST anomalies in summer, and meanwhile the south Pacific SST anomalies are negative, the entire arid/semi-arid region has more summer precipitation. When the central and eastern equatorial Pacific SST in preceding winter and preceding spring shows a warm anomaly and be weakened with the time goes on, but maintains to the summer, and the North Indian Ocean SST shows similar anomalies, the western part of arid/semi-arid area seems to have more rainfall in summer. When there is a warmer anomaly in central and eastern Pacific and a colder anomaly to the south, during the preceding spring the anomalies are weakened, a wide range of weak cold anomaly appeared in the eastern pacific, the eastern part of arid/semi-arid area seems to have more rainfall. Corresponding to the more summer rainfall years in the arid/semi-arid areas and the eastern part, the SST shows the same anomalous pattern except a small difference at the Southeast Pacific Ocean, but the anomalous pattern of the western part is quite different. |
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| Keywords: | arid/semi-arid area summer rainfall westerly jet stream wave train sea surface temprature anomaly |
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