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利用1961～2005年中国565个台站的逐日降水量观测资料,运用线性回归等统计方法对我国夏季(6～8月)降水进行了日雨量分级研究.按日雨量大小依次分成痕量(无记录)、微量(≤1 mm/d)、小雨(1.1～9.9 mm/d)、大雨(10～49.9 mm/d)、暴雨(50～99.9 mm/d)和大暴雨(≥100 mm/d)6个等级,而把小雨～大暴雨4个等级的雨日量总和称为有效雨日.年平均痕量雨日东西差异以东亚夏季风气候北缘为分界线,该线以西地区痕量雨日数大于以东地区.有效雨日的分布表现为西北地区最少,东部地区从西南至华南地区依次向北递减,其中东北地区东部的雨日数要大于西部.近45年来有效雨日的趋势分布表现为长江流域中下游、西北地区的新疆等地雨日增加,而黄河中下游等地区雨日减少.痕量雨日在我国基本为负趋势.微量雨日除我国西北地区为正趋势以外,其他地区均为负趋势.西北地区有效雨日增多主要来自于小雨雨日的贡献,长江-江南的有效雨日增多来自于大雨和暴雨雨日的贡献.西南和环渤海地区的有效雨日减少来自于大雨雨日的减少. 相似文献
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本文利用测站降水观测资料分析过去一百多年中国东部华北、长江流域以及华南夏季降水的年代际变化特征发现,尽管这三个地区的夏季降水具有不同的年代际转折时期,但是均同时在1910年代初期、1920年代初期、1940年代中期、1960年代中期、1970年代末期以及1990年代初期发生了跃变。近一百年间不同年代际时期东部夏季降水的分布型主要以南正北负或者南负北正的偶极型为主,并且无论是偶极型分布还是三极型分布,两个相邻年代际时期中国东部降水分布型发生完全反向变化的概率较高(60%)。此外,夏季的PDO、冬季的AO以及春季的北极海冰也同时在1920年代末期、1940年代中期、1970年代末期以及1990年代中期左右发生了跃变,这几次跃变时期与中国东部三个不同地区夏季降水发生跃变的时期一致,表现出近百年来太平洋年代振荡(PDO)、北极涛动(AO)以及北极海冰这三个因子对中国东部夏季降水年代际变化的协同作用。在年代际时间尺度上,夏季的PDO与华北夏季降水显著负相关。PDO的年代际变化能够在500 hPa位势高度场中激发出太平洋—日本(PJ)型年代际遥相关波列;同时在850 hPa风场中激发出类似于影响华北夏季降水年代际变化的大气环流型,从而影响华北降水的年代际变化。冬半年的AO与长江流域夏季降水存在显著正相关关系。冬季到春季正位相的AO导致亚洲大陆南部处于湿冷状态,土壤湿度的记忆性可将这种状态延续到夏季。因此,夏季海陆热力对比减弱,东亚夏季风发生年代际减弱,相应地长江流域的降水年代际增多。春季北极海冰与华南夏季降水显著负相关,北极海冰的年代际异常能在500 hPa位势高度场中激发出与静止Rossby波异常传播相联系的欧亚—华南年代际遥相关波列,从而影响华南降水的年代际变化。 相似文献
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An overview of dry-wet climate variability among monsoon-westerly regions and the monsoon northernmost marginal active zone in China 总被引：4，自引：2，他引：2 
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下载免费PDF全文 Climate in mainland China can be divided into the monsoon region in the southeast and
the westerly region in the northwest as well as the intercross zone, i.e., the monsoon northernmost
marginal active zone that is oriented from Southwest China to the upper Yellow River, North China,
and Northeast China. In the three regions, dry-wet climate changes are directly linked to the
interaction of the southerly monsoon flow on the east side of the Tibetan Plateau and the westerly
flow on the north side of the Plateau from the inter-annual to inter-decadal timescales. Some basic
features of climate variability in the three regions for the last half century and the historical
hundreds of years are reviewed in this paper.
In the last half century, an increasing trend of summer precipitation associated with the enhancing
westerly flow is found in the westerly region from Xinjiang to northern parts of North China and
Northeast China. On the other hand, an increasing trend of summer precipitation along the Yangtze
River and a decreasing trend of summer precipitation along the monsoon northernmost marginal active
zone are associated with the weakening monsoon flow in East Asia.
Historical documents are widely distributed in the monsoon region for hundreds of years and natural
climate proxies are constructed in the non-monsoon region, while two types of climate proxies can be
commonly found over the monsoon northernmost marginal active zone. In the monsoon region, dry-wet
variation centers are altered among North China, the lower Yangtze River, and South China from one
century to another. Dry or wet anomalies are firstly observed along the monsoon northernmost marginal
active zone and shifted southward or southeastward to the Yangtze River valley and South China in
about a 70-year timescale. Severe drought events are experienced along the monsoon northernmost
marginal active zone during the last 5 centuries. Inter-decadal dry-wet variations are depicted by
natural proxies for the last 4--5 centuries in several areas over the non-monsoon region.
Some questions, such as the impact of global warming on dry-wet regime changes in China, complex
interactions between the monsoon and westerly flows in Northeast China, and the integrated multi-proxy
analysis throughout all of China, are proposed. 相似文献
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Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. The last four grades together constitute the so called effective precipitation （〉 1 mm d^-1）. The spatial distribution and temporal trend of the graded precipitation days are examined. A decreasing trend in trace precipitation days is observed for the whole of China, except at several sites in the south of the middle section of the Yangtze River, while a decreasing trend in slight precipitation days only appears in eastern China. The decreasing trend and interannual variability of trace precipitation days is consistent with the warming trend and corresponding temperature variability in China for the same period, indicating a possible role played by increased surface air temperature in cloud formation processes. For the effective precipitation days, a decreasing trend is observed along the Yellow River valley and for the middle reaches of the Yangtze River and Southwest China, while an increasing trend is found for Xinjiang, the eastern Tibetan Plateau, Northeast China and Southeast China. The decreasing trend of effective precipitation days for the middle- lower Yellow River valley and the increasing trend for the lower Yangtze River valley are most likely linked to anomalous monsoon circulation in East China. The most important contributor to the trend in effective precipitation depends upon the region concerned. 相似文献
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In this study,we defined an index of the Antarctic Circumploar Wave(ACW) and analyzed its variability for the period 1951-2010.A regime shift of the circumpolar westerly in the Southern Ocean and an interdecadal change of the ACW,which occurred around the mid-1970s,were identified.Associated with these changes,the variations of the ACW show three distinct sub-periods:1951-1973,1974-1980,and 1981-2010.They are characterized by different speeds,amplitudes,and wave structures.We briefly investigated possible mechanisms responsible for the different behaviors of the ACW during the three periods. 相似文献
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气象文化建设是我们整个气象事业的一个重要组成部分，是我们气象部门文明创建的一个重要体现，也是我们每一个单位不可缺少的形象工程。不过，如何搞好气象文化建设，如何选准每一个单位气象文化建设的载体，则不能一刀切，不能干篇一律，千家一面，应因地制宜，因时而异。黄山市气象局在这方面进行了一些初步的探索和尝试，现不揣浅陋简述如下，以就教于大家。 相似文献
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