【作者】 韩艳凤；

【导师】 江志红；

【作者基本信息】 南京气象学院 ， 气象学， 2003， 硕士

【摘要】 利用东北地区99个测站的1960—2000年夏季逐日降水资料，以及NCEP再分析资料，采用旋转经验正交函数、Morlet小波分析、合成分析等方法分析了东北地区夏季降水的演变特征和降水异常的环流背景，得出主要结论如下：1 东北地区夏季降水存在着减少趋势，并且有14年和2～4年的周期存在，降水发生过两次突变现象，分别发生在1964年和1984／85年之间。2 东北地区夏季降水的季内演变特征为：东北地区夏季降水量的近24％集中在7月末期到8月上旬即主要集中在夏季第12、13、14候。6月到7月中旬降水主要集中在内蒙古地区，7月末期到8月中旬降水主要集中在辽宁地区。3 东北地区夏季降水变化可分为5种空间分布型：内蒙古东南部型，辽宁东部型，黑龙江东北部型，黑龙江西部型，和东北中部型。各区域降水的变化趋势不一致，其中辽宁东部地区降水减少最明显，内蒙古东南部降水增加趋势最明显。各区降水变化周期不同，黑龙江东北部存在16～18年的周期变化，其它地区存在10～14年的周期变化。各区域夏季降水出现突变的时间主要在60年代和80年代。东北地区不同区域大雨日数和大雨强度的长期变化趋势为辽宁地区大雨日数和强度变化趋势是减少趋势，东北中部大雨日数呈减少趋势，强度呈增加趋势。各不同区域大雨日数与夏季降水呈显著的正相关关系。4 东北地区夏季降水异常与大气环流背景有密切的关系，东北地区夏季多雨年在对流层中、高层冷空气比较活跃，高纬和极区主要由位势高度的正距平所控制，贝加尔湖以北的地区长波脊较为活跃，在东北地区和蒙古地区有异常的长波槽发展，极涡位置偏北、偏东；而在东北地区夏季少雨年则容易出现与上述相反的异常环流形式。5 东北地区夏季降水同Nino3区海温场有较好的正相关关系。多雨年发生在ENSO年和NO-ENSO年大气环流形式的不同主要表现在：ENSO年副热带高压较强，贝加尔湖地区南部低压槽容易加深；在NO-ENSO年副热带高压强度减弱，在西北太平洋和南海地区多热带系统活动。6 东北地区不同区域极端降水的时间分布存在月季差异，辽宁东部和黑龙江东北部地区主要出现在8月份，其它3个地区则出现在6月份。各区域产生极端降水的天气背景也不相同：内蒙古东南部的降水是前倾槽引起的强对流降水天气，辽宁和黑龙江东北部的降水是由于副热带高压和西风槽的共同作用引起的。黑龙江西部的降水是由于高空涡的直接作用引起的。更多还原

【Abstract】 Summer precipitation in Northeast China ranging from 1960a to 2000a and NCEP reanalysis data is applied to study the temporal and spatial features of summer rainfall and extreme precipitation in Northeast China. The results show:1 Summer rainfall in Northeast China exhibits upward trend with the cycle variation of 14 years and 2 to 4 years. Two abrupt changes occurs in summer rainfall with its happening time on 1964 and 1988/89.2 The intraseasonal variation features of summer precipitation in Northeast China are that the 24 percent of summer precipitation concentrate on late-July and first dek of August, i.e. the 12th, 13th and 14th pen of summertime. The summer precipitation in Northeast China mainly distribute in Inner-mogolio from Jjune to the middle of July and Liaoning from the end of July to the middle of Auguest.3 The change of summer rainfall in Northeast China falls into 5 types: The southeast of Inner-mogolio type, The east of Liaoning type, The northeast of Heilongjiang type, The west of Heilongjiang type and The centra] of Northeast China type. Different areas present different variation tendency of summer rainfall, among which the rainfall significantly decreases in the east of Liaoning and increases in southeast of Inner-mogolio. Meanwhile, the precipitation of different areas exhibits different cycle periods and different time of abrupt change. In the long-term variation trend of heavy rain days and its intensity, most areas present increase tendency with the exception of the area of Liaoning. There are positive correlation between heavy rain days and summer precipitation.4, The summer rainfall anomaly in Northeast China bears close correlation with the atmospheric circulation backgroud. While cold air in middle and high levels of troposphere is active in wet year with the positive anomalies over high-latitude and polar area, the active longwave ridge, the anomalous long-wave ridge in Northeast China and Inner-mogolia as well as the northward and eastward of the polar vortex, the contrary is in the dry year in Northeast China.5 The positive correlation exists between the summer rainfall in Northeast China and NINO3 SST. The atmospheric circulation of the wet year deviate from ENSO year to NO-ENSO year. In ENSO year, the Subtropical High is strong with the deepening of trough over south of Baikal Lake while in NO-ENSO year, the Subtropical High is weak with the high incidence of typhoons over northwest of Pacific and South China Sea.6, The intraseasonal discrepancy exists in the temporal distribution of extreme rainfall in Northeast China. While extreme rainfall appears in August in the east of Liaoning and the northeast of Heilongjiang, so does June in other three areas. Moreover, the weatherbackgrounds under which the extreme precipitation occurs are also different. While theprecipitation of southeast of Inner-mogolio is attributed as the strong convective precipitation,the rainfall of Liaoning and northeast of Heilongjiang is induced by Subtropical High andwesterly trough, and that of west of Heilongjiang is influenced directly by vortex in upperair.更多还原