Interdecadal Variability in Summer Precipitation over East China during the Past 100 Years and Its Possible Causes
Interdecadal Variability in Summer Precipitation over East China during the Past 100 Years and Its Possible Causes
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发表时间：
2014
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通讯作者：
Zhu Congwe
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作者：
Zhu Congwe
本文利用气象站资料分析了近百年来华北、长江流域和华南地区降水的年代际变化。结果表明：3个地区的降水在20世纪90年代初、20世纪20年代初、40年代中期、60年代中期、70年代末和90年代初发生了同步的年代际变化，但存在不同的年代际变化周期。近100年来，中国东部夏季降水在不同年代际的分布格局主要表现为“正南负北”或“正北负南”的偶极子。此外，无论是双极还是三极，在相邻的两个年代际周期中，完全相反的分布模式的概率更高（60%）。此外，夏季太平洋年代际涛动（PDO）、冬季北极年代际涛动（AO）和春季北极海冰也在20世纪20年代末、40年代中期、70年代末和90年代中期前后出现了同步变化，与中国东部3个地区夏季降水的转移周期一致，表明PDO、AO和北极海冰在过去100年中国东部夏季降水的年代际变化中发挥了协同作用。在年代际时间尺度上，华北夏季PDO与夏季降水呈显著负相关。PDO的年代际变率可能在500-hPa位势高度和850-hPa风场大气环流中产生太平洋-日本（PJ）互联型的年代际波列，这与影响华北夏季降水的年代际变化相似。因此，华北夏季降水呈现年代际变化。冬季AO与夏季降水呈显著正相关。当AO进入冬至春的正年代际期时，引起欧亚大陆南部降水增加和气温下降。由于土壤湿度的记忆，欧亚大陆南部的寒冷和潮湿状态从冬天持续到夏天。造成夏季海陆对比减弱。因此，东亚夏季风经历了年代际减弱。相应的，长江流域降水呈现年代际增加的趋势。春季北极海冰与夏季华南降水呈显著负相关。北极海冰的年代际变化可以产生欧亚大陆-华南互联型的年代际波列，与500 hpa位势高度的静止rosby波的异常传播有关，从而影响华南降水的年代际变化。
In this paper,the interdecadal variations of rainfall over North China,the Yangtze River valley,and South China during the past 100 years are examined using weather station data.The results show that the rainfall over these three regions underwent simultaneous shifts in the early 1910 s,the early 1920 s,the middle 1940 s,the middle 1960 s,the late 1970 s,and the early 1990 s,although there are different interdecadal shifting periods.During the past 100 years the distribution patterns of summer rainfall over eastern China are primarily characterized by dipoles,such as "positive south and negative north" or "positive north and negative south" in different interdecadal periods.Furthermore,the probability of the totally reverse distribution patterns during two adjacent interdecadal periods is higher(60%) whether they are dipolar or tripolar.In addition,summer Pacific Decadal Oscillation(PDO),winter Arctic Oscillation(AO),and spring arctic sea ice also showed synchronous shifts around the late 1920 s,the middle 1940 s,the late 1970 s,and the middle 1990 s,consistent with the shifting periods of summer precipitation over three regions of eastern China,suggesting that PDO,AO,and arctic sea ice have played a synergetic role in the interdecadal variation of summer rainfall over eastern China during the past 100 years.At interdecadal time scales,PDO in summer is significantly negatively correlated with summer rainfall in North China.The interdecadal variability of PDO may generate interdecadal wave trains of Pacific-Japan(PJ) interconnection pattern at 500-hPa geopotential height and atmospheric circulation in the 850-hPa wind field,which is similar to that affecting the interdecadal variation of summer rainfall over North China.Consequently,summer rainfall over North China showed interdecadal variation.The AO in wintertime is significantly positively correlated with summer rainfall over the Yangtze River valley.When AO enters its positive interdecadal phase from winter to spring,it causes an increase of precipitation and a decrease in temperature over the southern Eurasian continent.The cold and wet state over the southern Eurasian continent persists from winter to summer because of the memory of soil humidity.It causes the weakening of sea–land contrast in summer.As a result,the East Asian summer monsoon experiences interdecadal weakening.Correspondingly,the rainfall over the Yangtze River valley shows interdecadal increase.Spring Arctic sea ice is significantly negatively correlated with summer rainfall over South China.Interdecadal variation in Arctic sea ice can generate interdecadal wave trains of the Eurasia–South China interconnection pattern associated with the anomalous propagation of stationary Rossby waves at 500-hPa geopotential height,which affects the interdecadal variation in rainfall over South China.