【作者】 陈晓燕；

【导师】 王式功；

【作者基本信息】 兰州大学 ， 气象学， 2012， 硕士

【摘要】 由极端降水事件导致的洪涝和泥石流是重大的气象灾害,给社会、经济和人民生活带来的影响严重、损失巨大。进一步加强对极端降水事件的研究,揭示极端降水事件的成因和变化规律,可为极端降水事件的预测和防洪减灾提供科学依据。本文利用中国北方293个气象站1959-2008年逐日降水资料和NCEP/NCAR逐日再分析资料,提出了适合北方干旱与半干旱区相关台站的极端降水阈值,研究了中国北方降水日数和极端降水事件的时空特征,分析了发生极端降水时的大气环流特征以及极端降水事件与气候因子的关系,结果表明：1)中国北方总降水日数和不同等级降水日数在空间上都是由东向西递减；年降水量、总降水日数和不同等级降水日数,在西部地区呈增加趋势,特别是西北西部的小雨日数增加明显,其它地区则表现为减少趋势。2)北方地区极端降水日数和年极端降水量由西向东逐渐增大,且呈带状分布；极端降水日数占总降水日数比重、极端降水量占年降水量比重也由西向东逐渐增大。3)四个气候区极端降水日数与降水量的时间变化特征存在明显差异,极端降水日数和极端降水量主要集中在夏季；极端降水日数与降水量在西北西部表现为增加趋势,而在西北东部、华北和东北三个气候区则表现为减少趋势。4)四个气候区出现极端降水的环流形势如下：西北西部,巴尔喀什湖-帕米尔高原之间的低槽延伸到40°N以南,印度洋季风较强；西北东部,西北东部受低槽控制,深厚槽可向南延伸到30°N附近,30°N以南的地区则受高压控制,孟加拉湾上空西风和偏南风盛行,与西太平洋副高西北部的东南气流汇合北上；华北气候区,中国境内环流形势西低东高,低槽从东北伸向四川,槽前西南风的风力较强,副高脊线位于30°N附近；东北气候区,东北地区处在低压控制下,孟加拉湾上南支槽存在,与副热带高压西侧的偏南气流汇合北上,将大量的水汽输送到东北地区。5)四个气候区极端降水站日数与西太平洋副高和南海副高的强度指数及北界位置呈正相关；西北西部气候区与Nino4区的海表温度正遥相关最好,其它三个气候区与Nino34区的海表温度正遥相关最好。更多还原

【Abstract】 The flood and mud-rock flow caused by extremely precipitation events influences a lot and cause large lost and damages to the society, economy and our lives. Further researches for investigating the variability and mechanism of the extremely precipitation events is helpful and important for forecasting the extremely precipitation events and can support us to reduce the lost and damages caused by flood and other subsequent destructions. By using the rainfall data of293stations in northern China from1959to2008and NCEP/NCAR daily circulation reanalysis data, the extreme precipitation threshold which was suitable for related stations in Arid and Semi-arid Areas in Northern China was put forward, the temporal and spatial characteristics of precipitation days and extreme precipitation events in recent50years were researched, the atmospheric circulation features were analyzed when extreme precipitation event occurred and analyzed the correlation between extreme precipitation event and climate factors, results show that:1) the total precipitation days and different intensity precipitation days in space are decreasing from east to west in northern China, and show increasing trend in West China, but have an decreasing tendency in other places,the light rain days have increased mutation in Northwest Western.2) the extreme precipitation threshold, extreme precipitation days and yearly extreme rainfall are gradually increasing from the northwest to the southeast in northern regions, and distributes in belts; the proportion of extreme precipitation days to total rain days, and the proportion of extreme rainfall to annual rainfall are also increased gradually from west to east in four climatic regions.3) the temporal changes of extreme precipitation days and yearly rainfall have the obvious differences in four climatic regions, the days of extreme precipitation and extreme rainfall mainly concentrates in summer; the extreme precipitation days and yearly rainfall show increasing trend in Northwest Western, but have an decreasing tendency in the east part of northwest, North and northeast three climate zones. 4) the circulation characteristics of extreme precipitation event when it appears in Northwest Western:the low trough Lake between Balkhash-Pamirs plateau extends to south of40°N, the India monsoon is stronger; the circulation characteristics of extreme precipitation event when it appears in Eastern Part of Northwest China:the low trough covers on the Eastern part of Northwest China, the deep low trough could extend south to30°N, the south of35°N area is controlled by high pressure,westerly and southerly wind prevails over the bay of Bengal, which is formed by combining the southeast air current from north part of Northwest Pacific subtropical high, and northward moving, the circulation characteristics of extreme precipitation event when it appears in the North China:the circulation situation is lower in west and higher in east over China, the low trough is extending from the northeast to Sichuan, the southwestly wind ahead of it is more stronger, Subtropical High Ridge Locates at30°N; the circulation characteristics of extreme precipitation event when it appears in Northeast China:the low pressure covers on the Northeast China, there is a southern trough over the bay of Bengal, the southwest air current front of the southern trough,which is formed by combining the southeast air current from west part of Northwest Pacific subtropical high, and northward moving,the amount of water vapor is transported to the Northeast China by them.5) there is a positive correlation between the extreme precipitation events of four climatic regions and subtropical high pressure intension index, South China Sea intensity index,and the position of the northern boundary; Western Northwest China climate zone and Nino4zone of the sea surface temperature is related to the best, the other three climate zone correlated best with Nino34zone of the sea surface temperature.更多还原