长江中游和下游夏季降水季节内振荡特征

发布时间：2018-03-15 12:55

本文选题：全国夏季降水　切入点：长江中下游　出处：《中国气象科学研究院》2017年硕士论文　论文类型：学位论文

【摘要】：本文利用1979-2013年中国气象局提供的824站点逐日降水观测资料和NCEP/NCAR再分析资料,分析了全国夏季(5-10月)降水季节内振荡最显著周期的分布特征,着重探讨了长江中游和长江下游的夏季降水所具有的不同季节内振荡周期,以及与季节内降水相联系的环流场差异。通过对全国824个台站的35年夏季降水进行季节内尺度的诊断分析,发现全国夏季降水在季节内振荡的周期分布上存在一定的规律。季节内振荡最强的区域位于长江以南地区。使用10-90天Lanczos带通滤波提取降水的季节内振荡分量,并使用功率谱分析得到降水季节内振荡的最显著周期,发现全国大部分地区的季节内振荡周期集中在30天以内,长江中游地区的振荡周期为10-30天,长江下游振荡周期为30-60天,华南地区的振荡周期为20-30天。对长江流域的中游和下游夏季降水具有不同的显著振荡周期这一分布特征,进行了分析和诊断。利用位相合成等方法来揭示这两个区域在不同周期的季节内振荡降水、高低空风场和高度场以及垂直结构和水汽等循环过程的演变特征。在200 hPa环流场上,长江中游的季节内尺度降水主要受到高纬度自西向东传播的波列影响,而长江下游的季节内尺度降水与鄂霍次克海的高度场的变化存在密切关系。在风场的垂直涡度和散度的位相结构演变过程中,10-30天的垂直涡度和散度有自北向南的移动,而30-60天的垂直涡度和散度在长江以南地区有自南向北的传播。水汽输送的位相发展过程表明,长江中游的水汽分别来自于南海的向北输送和长江以北地区向南的水汽输送;而长江下游地区的水汽则主要来自于热带东印度洋经孟加拉湾的向东输送并在南海的北向输送,以及西太平洋水汽向西经南海再向长江下游的输送。另外从高层大尺度环流场和整层积分的水汽通量输送上解释了长江中游10-30天季节内尺度降水的自北向南移动,和长江下游30-60天季节内尺度降水自南向北传播的原因。
[Abstract]:Based on the daily precipitation observation data and NCEP/NCAR reanalysis data from 824 stations provided by China Meteorological Administration from 1979 to 2013, this paper analyzes the distribution characteristics of the most significant periods of precipitation intraseasonal oscillation in summer in China. The different intraseasonal oscillation periods of summer precipitation in the middle reaches of the Yangtze River and the lower reaches of the Yangtze River are emphatically discussed. And the difference of circulation field associated with seasonal precipitation. Through the diagnostic analysis of 35 years summer precipitation in 824 stations in China, It is found that there is a certain regularity in the periodic distribution of the intraseasonal oscillation of summer precipitation in China. The region with the strongest seasonal oscillation is located in the area south of the Yangtze River. The intraseasonal oscillation component of the precipitation is extracted by 10-90 days Lanczos bandpass filter. Using power spectrum analysis, the most significant periods of intraseasonal oscillation of precipitation are obtained. It is found that the period of intraseasonal oscillation is concentrated within 30 days in most areas of China, the period of oscillation is 10-30 days in the middle reaches of the Yangtze River, and the oscillation period of the lower reaches of the Yangtze River is 30-60 days. The oscillation period in South China is 20-30 days. The phase synthesis method is used to reveal the evolution characteristics of seasonal oscillating precipitation, high and low air wind field, height field, vertical structure and water vapor in the two regions. The seasonal internal scale precipitation in the middle reaches of the Yangtze River is mainly affected by wave trains propagating from west to east in high latitudes. The seasonal internal scale precipitation in the lower reaches of the Yangtze River is closely related to the variation of the height field in the Okhotsk Sea. During the evolution of the vertical vorticity and divergence of the wind field, the vertical vorticity and divergence of the wind field move from north to south in 10-30 days. The vertical vorticity and divergence of 30-60 days propagate from south to north in the south of the Yangtze River. The phase development process of water vapor transport indicates that the water vapor in the middle reaches of the Yangtze River comes from the northward transport of the South China Sea and the water vapor transport from the north of the Yangtze River to the south. The water vapor in the lower reaches of the Yangtze River is mainly transported eastward from the tropical eastern Indian Ocean through the Bay of Bengal and northward in the South China Sea. And the transport of water vapor from the western Pacific to the South China Sea and then to the lower reaches of the Yangtze River. In addition, from the large-scale circulation field at the upper level and the integrated water vapor flux transport in the whole layer, it is explained that the internal scale precipitation in the middle reaches of the Yangtze River moves from north to south during the 10-30 days of the season. And the causes of the internal scale precipitation propagating from south to north in 30-60 days in the lower reaches of the Yangtze River.
【学位授予单位】：中国气象科学研究院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P426.6

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