【作者】 廖荣伟；

【导师】 赵平；

【作者基本信息】 中国气象科学研究院 ， 气象学， 2011， 博士

【摘要】 本文利用NECP/NCAR1、NECP/NCAR2、ECMWF(ERA40)的再分析资料,以及中国160台站月平均降水资料和中国757台站夏季(6～8月)月平均降水资料,运用经验正交函数分解(EOF)、小波分析、奇异值分解(SVD)、M-K检验等统计方法以及相关、合成诊断方法,对中国东部季风湿润区大气水分收支的气候特征,水汽输送及降水的时空分布特征进行了较为系统的分析研究。其中着重分析了冬季、夏季大气水分收支高低值年(代)对应的水汽输送异常、大气环流异常、冬夏季风强弱、经向风异常和降水异常等问题。运用RegCM3模式对中国东部季风湿润区冬夏大气水分收支高低值年(代)对应的水汽输送、水汽通量散度及降水进行了模拟试验。全文主要结论归纳如下:⑴中国东部季风湿润区多年平均的大气水分收支,年总和与四季均为水分收入。水汽输送在春季和夏季最强,大气水分收入最多,对净收入的贡献最大;秋季和冬季的水汽输送较弱,大气水分收入较少。⑵多年平均的季风湿润区南边界为主要的水汽输入区;西边界全年水汽输入,东边界水汽输出。水汽输送计算得到的大气水分收支年循环在2～10月为水分收入,水汽通量散度和P? E计算得到的大气水分收支在2～9月为水分收入。⑶水汽输送和水汽通量散度计算的大气水分收支垂直分布情况较为接近。四季的大气水分收支垂直分布各不相同,在对流层低层,春季和夏季以水分收入为主,秋季和冬季以水分支出为主;在对流层中上层,四季均以水分收入为主。整个区域在850hPa为水分支出外,其余各层均为水分收入。四季大气水分收支的长期变化趋势明显,在几十年里表现出显著的线性趋势。⑷对年总和及四季大气水分收支时间序列进行M-K检验,揭示了存在的突变现象;通过小波分析,发现上述时间序列的周期表现为2～4年。⑸运用EOF方法对冬、夏季降水场,水汽输送场进行分解,揭示了冬、夏季水汽输送及降水的异常时空分布特征。运用SVD分解,发现冬、夏季经纬向水汽输送与降水的第一对奇异向量场具有同相变化关系。⑹冬季大气水分收支时间序列的高低指数年能够指示季风湿润区经向风的异常变化,还能够指示东亚冬季风的强弱和降水的异常变化。高值年,蒙古冷高压和阿留申低压偏弱,东亚大陆对流层低层盛行异常偏南风。季风湿润区30°N以南有强烈地上升运动,配合南海、孟加拉湾的暖湿水汽输送,可使大气水分收入增多,造成降水异常增加;而低值年则相反。合成的异常水汽输入集中在900～600hPa之间,其中西、南边界为水汽输入区,而东、北边界为水汽输出区。合成的大气水分收入的经向变化占净收入变化的91.3%。合成的异常降水中心量值可达40mm以上,而水分收支年代际变化合成的异常降水中心量值可达30mm以上。冬季的平均流造成季风湿润区水汽辐合,瞬变波造成水汽辐散。高值年季风湿润区的瞬变偏南水汽输送强,南海的瞬变偏南水汽输送弱;低值年则相反。⑺夏季大气水分收支时间序列的高低指数年能够指示中国东部季风湿润区经向风的异常变化,对季风湿润区的降水变率具有指示意义。合成的整层水汽输送在东亚–西太平洋区表现为经向三极子型。不同层次的大气环流异常有利于外部的异常水汽输入,可造成大气中的水分增多,降水增加。降水的差异由经向水分收入与支出的变化造成,纬向的收支变化对此差异贡献只有经向的1/4。⑻夏季高值年代,东亚夏季风偏弱,副热带高压偏西、偏强,亚洲热低压偏弱,对流层低层为异常气旋式辐合,异常偏南风盛行,外界有较多水汽输入,上升运动强烈,有利于降水的产生;低值年代则相反。合成的边界水汽异常输入输出主要集中在900～500hPa之间。高值年代,5月以前的降水偏少,对应经纬向水汽输送负异常,6～8月偏多,对应经纬向水汽输送正异常,10月以后经纬向水汽输送正异常,降水负异常;低值年代则相反。⑼夏季瞬变水汽通量高值区较冬季北抬,瞬变波造成水汽辐散。夏季高值年代季风湿润区的瞬变偏南水汽输送强,南海的偏西水汽输送强。根据NECP1、NECP2、ERA-40资料得出的大气水分收支时间序列具有相同的变化趋势,在水汽输送、水汽通量散度的合成场上分布形式较为一致。⑽RegCM3模式对于冬、夏季季风湿润区降水的分布具有较好的模拟能力。SWT2模拟结果的水汽输送场比SWT1与再分析资料结果相似性更好,揭示了夏季更大的海陆热力差异可能是影响大气环流发生异常的原因之一。更多还原

【Abstract】 Using daily and monthly means of the reanalysis datasets from the NCAR/NCEP1、NECP/NCAR2、ECMWF(ERA40),rainfall data from 160 and 757(June～August)surface stations in China for the period 1958 to 2007 and referring to atmospheric circulations in eastern China monsoon wetness region. We use the empirical orthogonal function decomposition (EOF), wavelet analysis, singular value decomposition (SVD), Mann-Kendall test and other statistical methods and related synthetic、composite diagnosis methods, systematic analyzing the climatic character of moisture budgets in Eastern China monsoon wetness region and the spatial temporal distribution of precipitation and water vapor transport. We analyze the winter and summer moisture balance in high and low values years(decadal years) which corresponding to water vapor transport anomaly, atmospheric circulation anomalies, winter and summer monsoon strength, the meridional wind anomalies, precipitation anomalies and so on. At the same time, we use the RegCM3 mode to simulation the winter and summer anomaly of water vapor transport、moisture flux divergence and precipitation in high and low values years(decadal years) in Eastern China monsoon wetness region.The major conclusions can be summarized as follows:⑴For yearly moisture budgets in this area, moisture has incoming, and the same results for spring, summer, autumn, winter. Based on different method to calculate moisture balance, we have got that water vapor transport and moisture budgets are stronger in spring and summer, while in winter and autumn are relative weak.⑵For the meridional water wapor transport, water vapor enters this area mainly in south boundary, and enters through west boundary and departs from east boundary all the year For the zonal. For whole area, the moisture budget which is calculated by water wapor transport method is positive from February to October. Meanwhile, moisture budgets which are calculated by moisture flux divergence method or P ? Emethod, the results are positive in February to September in the same time.⑶Based on water wapor transport and moisture flux divergence methods which calculate the vertical distribution of moisture budgets under climatically, the values manifest positive anomaly between 800～500hPa. We have got that moisture output at 850hPa, other layers input under climatically. The vertical distribution of moisture budgets is different for seasons, the values manifest positive in the lower troposphere in spring and summer, while manifesting negative in autumn and winter. The values manifest positive in the upper troposphere for seasons. The interannual variability of four seasons is explicitly and shows a significant linear trend in the decades.⑷Using M-K tests to analyze the the time series of moisture budgets for annual and four seasons, revealed the existence of abrupt change from each time series; Using wavelet analysis, revealed the period of each time series mainly in 2 to 4 years.⑸Using EOF method in winter and summer to analyze precipitation and water vapor transport field, revealed the character of the temporal and spatial distribution. Using SVD method in winter and summer to analyze precipitation and water vapor transport field, found out that there have a relationship with the phase change.⑹The high values of moisture budgets are not only reflecte the variations of the anomaly of meridional winds but also indicate an intensity of winter monsoon and an anomaly of rainfall along the valleys in the Eastern China monsoon wetness region. Corresponding to the higher value years, the high and cold pressure centering in Mongolia and the low pressure centering in Aleutian are weaker. Meanwhile, the southerly wind anomalies prevail in the lower troposphere and anomaly cyclone circulation in the vertical troposphere over the mainland of China, therefore intensifying the convergence and upward motion in south of 30°N and coordinating with the water vapor transport of Bay of Bengal and South China Sea. It causes the moisture budgets and anomaly rainfall to increase, but the lower value years are oppositely. The difference in composites for water vapor transport importes between 900 to 600 hPa, western or southern boundary is the major input region, the remains are the contrary. The larger difference in composites for moisture budgets is in meridional, accounting for 91.3% for net incoming change, the difference in composites for the zonal moisture budgets is smaller. The difference in composites for rainfall is above 40mm in center. The difference in composites for decadal rainfall is above 30mm in center. The mean flow brings about moisture convergence, and transient eddy brings about divergence. In higher value years, the southerly transient eddy of water vapour transport is weaker in the South China Sea, and stronger in the eastern China.⑺The moisture budgets sequence display the significant interannual variations in summer, Not only reflecte the variations of the anomaly of meridional winds but also indicate an intensity of summer monsoon and an anomaly of rainfall along the valleys in the Eastern China monsoon wetness region. The difference between high and low values of integrated water vapor transport to East Asia-Western Pacific Region shows the three-pole type. Different levels of atmospheric circulation anomalies in composite are conducive to water vapor input, increaseing the moisture and precipitation. Differences between high and low values of precipitation in composite mainly causes to the change of income and expenditure meridional moisture budgets, but the change of zonal budget contributes to this difference only by 1/4.⑻The interdecadal variations of summer moisture budgets, in high value era, the summer monsoon is weak, subtropical high is wester and stronger; Asian thermal low pressure is weak, the lower troposphere appears anomalous cyclonic circulation, and prevails anomalous southerly wind, as more water vapor enter from the outside, accompanies with the strong upward motion, so it is easy to the generation of precipitation. The difference in composite for water vapor transport importes between 900 to 500 hPa, Accompanying with the difference and significant anomaly for rainfall, the main reason is changes by the incoming and expenditure in meridional moisture budgets. Before May, the precipitation is less than normal, corresponding to the negative anomaly of water vapor transport in meridional and zonal; between June to August, the precipitation is more than normal, corresponding to the positive anomaly of water vapor transport; after October, the precipitation is negative and water vapor transport is positive. But the low value era is oppositely.⑼The high values region of water vapor flux by transient eddy northerly in summer than winter. In higher value era, the southerly and westerly transient eddy of water vapour transport is stronger in the eastern China and the South China Sea. The interdecadal variability of moisture budgets can reflect from NECP1、NECP2、ERA-40 reanalysis datasets, and the same difference of distribution in composite for water vapor transport and moisture flux divergence.⑽RegCM3 model has a good ability to simulate the interdecadal variation of precipitation, the difference in composite for SWT2 is better than SWT1, it can reveal one of the reasons that land-sea thermal difference will affect the atmospheric circulation anomalies in summer.更多还原