doi:  10.3878/j.issn.1006-9895.1511.15257
夏季长江中下游地区降水持续性年(代)际变异及其与环流和Rossby波活动的联系

Interannual and Interdecadal Variations of Summer Rainfall Duration over the Middle and Lower Reaches of the Yangtze River in Association with Anomalous Circulation and Rossby Wave Activities
摘要点击 543  全文点击 498  投稿时间:2015-08-26  
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基金:  公益性行业(气象)科研专项GYHY201406024,国家自然科学基金项目41330425,江苏省研究生科研创新计划项目CXZZ12_0485,灾害天气国家重点实验室课题2015LASW-A03
中文关键词:  长江中下游地区  降水持续性  Rossby波活动
英文关键词:  Middle and lower reaches of the Yangtze River  Rainfall duration  Rossby wave activity
        
作者中文名作者英文名单位
李明刚LI Minggang南京信息工程大学江苏省气象灾害预报预警协同创新中心, 南京 210044;中国气象科学研究院灾害天气国家重点实验室, 北京 100081
管兆勇GUAN Zhaoyong南京信息工程大学江苏省气象灾害预报预警协同创新中心, 南京 210044;南京信息工程大学气象灾害省部共建教育部重点实验室, 南京 210044
梅士龙MEI Shilong嘉兴市气象局, 嘉兴 314050
引用:李明刚,管兆勇,梅士龙.2016.夏季长江中下游地区降水持续性年(代)际变异及其与环流和Rossby波活动的联系[J].大气科学,40(6):1199-1214,doi:10.3878/j.issn.1006-9895.1511.15257.
Citation:LI Minggang,GUAN Zhaoyong,MEI Shilong.2016.Interannual and Interdecadal Variations of Summer Rainfall Duration over the Middle and Lower Reaches of the Yangtze River in Association with Anomalous Circulation and Rossby Wave Activities[J].Chinese Journal of Atmospheric Sciences (in Chinese),40(6):1199-1214,doi:10.3878/j.issn.1006-9895.1511.15257.
中文摘要:
      旱涝异常不仅与降水的频次和强度有关,在多种时间尺度上,其与降水的持续性亦存在较好的对应关系。基于1979~2013年6~7月中国东部249站点逐日降水资料及ERA-interim逐月再分析资料,研究了长江中下游地区近35年降水持续性的长期变化及其相联系的大尺度环流型和Rossby波能量频散特征。结果表明:近35年长江中下游地区降水时段平均持续时间变短而无雨时段变长,体现出了降水持续性的减弱趋势。进一步研究发现,该趋势变化与长江中下游地区在1980和1990年代持续性降水事件偏多,而在2000年以后偏少的年代际变化有关。在年代际和年际尺度上,与长江中下游地区降水持续特征变异相联系的异常环流型在我国东南部及南海地区分布较为类似,而在偏高纬度和偏低纬度地区存在较大差异。相似之处在于:在两个时间尺度上,在对流层中高层均存在显著的反气旋性环流控制我国东南部地区,而在中低层均存在由海洋向长江中下游地区的气流辐合,并在高层由长江中下游地区向海洋辐合。不同之处是:年代际尺度上,自对流层低层到高层在乌拉尔山以东及蒙古地区分别存在反气旋性环流和气旋性环流,且赤道印度洋地区的对流层中低层存在显著的气旋性环流;而在年际尺度上,由低层到高层位于贝加尔湖东、西侧均为反气旋性环流异常,但海洋性大陆的东北部,低层出现向长江中下游地区辐合的气流的源,高层则为由长江中下游地区向低纬度地区辐合的气流的汇。Rossby波扰动能量频散特征在年代际和年际尺度上亦呈现出明显的差异。年代际尺度上,中纬度地区自大西洋至蒙古地区存在一个正—负—正—负的Rossby波列,波能东传,对长江中下游地区产生影响,而在中低层,自低纬地区向长江中下游地区的波能传播相对较弱;在年际尺度上,影响长江中下游地区降水的Rossby波活动的局地性特征更为明显。在低层,波扰能量经由南海向长江中下游地区传播更明显,而在对流层高层源于贝加尔湖西侧的波扰能量传播相对较强。这些结果有助于深刻认识长江中下游地区降水的异常持续及与之相联系的洪涝灾害的形成机理。
Abstract:
      Droughts and floods are not only related to abnormal rainfall frequency or intensity,but also associated with the duration of rainfall on multiple timescales.Based on daily rainfall data collected at 249 stations in eastern China and the ERA-interim reanalysis,the long term changes in rainfall duration over the middle and lower reaches of the Yangtze River (hereafter MLRYR) and associated large scale circulation patterns and Rossby wave energy dispersion have been investigated.In the recent 35 years,the average duration of summertime wet spells decreases while that of dry spells increases,indicating a decreasing (negative) trend of rainfall duration over the MLRYR.Further analysis shows that this trend is related to inter-decadal changes in the frequency of persistent rainfall extremes,which is obviously higher in the 1980s and 1990s and lower in the 2000s.The anomalous circulation patterns that describe the inter-decadal and inter-annual changes in rainfall duration over the MLRYR look similar in some regions including Southeast China and the South China Sea,but different between mid-to high-latitudes and lower-latitudes.On both inter-decadal and inter-annual timescales,southeastern China is under control of a notable anticyclonic circulation anomaly in the middle and upper troposphere.The airflow converges into the MLRYR in the middle and lower troposphere and diverges in the upper troposphere with air flowing away from the MLRYR to the ocean.However,associated with inter-decadal changes,an anomalous anticyclonic circulation is located to the east of the Urals while an anomalous cyclonic circulation is found over Mongolia in the lower and upper troposphere.Meanwhile,an anomalous cyclonic circulation can be found over the equatorial Indian Ocean in the middle and lower troposphere.In contrast,on the inter-annual timescale,anomalous anticyclonic circulation can be found on both the east and west sides of Lake Baikal in the lower and upper troposphere.Divergence occurs in the lower troposphere over northeastern Maritime Continent with the air moving towards the MLYRV,whereas convergence develops in the upper troposphere and the air flows away from the MLRYR to lower latitudes.Characteristic Rossby wave propagation and energy dispersion demonstrate significant differences between inter-decadal and inter-annual timescales.On the inter-decadal timescale,a Rossby wave train with alternatively positive-negative-positive-negative geopotential height anomaly can be found in the mid-latitude from the Atlantic to Mongolia.The eastward propagation of waver energy affects the MLRYR.In the mid-and lower troposphere,however,the wave energy dispersion from lower latitudes to MLRYR is relatively weak.On the inter-annual timescale,the Rossby wave activity flux demonstrates more distinct local features.In the lower troposphere,strong wave energy propagates from South China Sea in the lower latitudes to the MLRYR.In the upper troposphere,wave energy dispersion from regions to the west of Lake Baikal to MLRYR is more obvious.These results are helpful for our better understanding of the mechanism for the persistent rainfall anomaly and related droughts/floods over the MLRYR.
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