长江流域中下游梅雨时期500毫巴环流形势的分析

本文对1954—1962年5—7月500毫巴流型作了分析,确定了长江中下游各年的梅雨期,划分了梅雨期500毫巴环流型。分析指出,西太平洋副热带高压和东亚上空西风气流的变化,是决定入梅和出梅的重要因素,其中东经110°到125°之间的副热带高压脊线的变化更重要。当这个脊线从低纬度向北移动,越过北纬20°时,梅雨开始,再次北移越过北纬25°时,梅雨结束。500毫巴西风气流的变化是另一个指标。90°E上南支强西风消失,东风突然向北推进,是季节转换的标志,这以后,当115°—125°E上南支强西风北撤到北纬30°以北时,梅雨开始,再次北撤越过北纬35°时,梅雨就结束。     

夏季亚洲南部100毫巴流型的变化及其与西太平洋副热带高压进退的关系

通过对夏季亚洲南部100毫巴流型变化的研究,我们发现夏季我国西藏高原上空的反气旋是北半球副热带地区势力最强并稳定的大气活动中心。这个高空反气旋绕着其平均位置来回振动。在振动过程中,亚洲南部的100毫巴流型发生调整,并表现成两类基本的流型,其中第一类流型表现反气旋偏离高原,这时候在高原东西两侧(50°E和110°)各有新的反气旋建立,而在高原上则是低气压区;第二类流型表现在反气旋重新返回高原上空。在这两类流型转变期间,西太平洋副热带高压脊在中国大陆上出现一次进退过程,而且每年我国长江流域梅雨期的结束也与上述第一类流型的建立有联系。其次,我们对中国大陆上西太平洋副热带高压进退过程与100毫巴流型变化的关系进行了研究,发现两者关系甚密切。当100毫巴第一类流型出现时,西太平洋副热带高压北进西伸。而在第二类流型出现时,西太平洋副热带高压向东南撤退。根据这些关系并结合我国预报员有关副热带高压进退的预报经验,我们提出有关副热带高压进退预报的几个依据。     

夏季亚洲大陆上空大气环流的结构

作者分析了1951—55时期中850、700及500毫巴的7月平均气流场的构造,以及1956年7、8两月亚洲上空200毫巴平均等高线图.又作了1956年7、8两月东经75度、90度、105度和120度经线上平均风场和温度场的剖面.我们发现,在夏季有三种基本气流组成亚洲大陆上空三度空间的气流场:即,(1)中纬度的西风气流,(2)高空热带和副热带的东风气流,(3)位于高空热带和副热带东风气流下面的西南季风.此外,对于1956年从春季到夏季的过渡时期中,亚洲上空大气环流的转变,亦作了研究.我们发现,从春季到夏季的过渡时期中,亚洲上空的大气环流有着一个跳躍的转变.在这个时期中,喜马拉雅山南边的高空副热带西风急流向北撤退,在西藏高原的纬度上空,建立一个副热带高压脊线,并且在亚洲南部上空(北纬12度以南)建立一支高空东空急流.同时印度的西南季风和我国长江流域的梅雨时期开始出现.作者又发现,夏季在中国大陆上,雨带的北移和西风带北撤以及相应的西风带强度的削弱有着密切的联系.     

Interannual and interdecadal variations of the South Asian and western Pacific subtropical highs and their relationships with Asian-Pacific summer climate

In this study, interdecadal and interannual variations of the South Asian high (SAH) and the western Pacific subtropical high (WPSH), as well as their relationships with the summer climate over Asian and Pacific regions, are addressed. The variations of SAH and WPSH are objectively measured by the first singular value decomposition (SVD) mode of geopotential heights at the 100- and 500-hPa levels. The first SVD mode of summertime 100- and 500-hPa geopotential heights represents well the relationship between the variations of SAH and WPSH. Both SAH and WPSH exhibit large interannual variability and experienced an apparent long-term change in 1987. The WPSH intensifies and extends westward when SAH intensifies and extends eastward, and vice versa. The India?CBurma trough weakens when WPSH intensifies. The changes in SAH and WPSH at various levels are linked to broad-scale increases in tropical tropospheric temperature and geopotential height. When SAH and WPSH strengthen, monsoon flow becomes weaker over eastern Asia. In the meantime, precipitation decreases over eastern South China Sea, Philippines, the Philippine Sea and northeastern Asia, but increases over China, Korea, Japan and the ocean domain east of Japan. Similar features are mostly found on both interdecadal and interannual timescales, but are more evident on interannual timescale.     

Intercomparison of the Summertime Subtropical High from the ERA-40 and over East Eurasia and the western North Pacific

An intercomparison of summertime (JJA)subtropical geopotential heights from the ERA-40 and NCEP/NCAR reanalysis is specifically conducted over East Eurasia and the western North Pacific. The NCEP/NCAR is obviously lower than the ERA-40 in the mid-to-lower troposphere in most regions of East Eurasia before the mid-1970s, but becomes higher than the ERA-40 after the mid-1970s and thus demonstrates stronger increased trends during the period of 1958-2001. Both reanalyses are lower than the observations in most regions of China. The NCEP/NCAR especially shows tremendously systematic lower values before the mid-1960s and displays abrupt changes before the 1970s. Several indices of the western North Pacific subtropical high (WNPSH), calculated from both reanalyzed summer geopotential heights, also reveal that the variation trend of the NCEP/NCAR is stronger than that of the ERA-40 in the mid-to-lower troposphere from 1958 to 2001. Through singular value decomposition (SVD) analysis, the summer geopotential heights at 500 hPa from the ERA-40 are better than the NCEP/NCAR counterparts at interacting with the precipitation over the East Asian monsoon region. The results indicate that the NCEP/NCAR in the mid-and-lower troposphere may overestimate interdecadal changes and should be used cautiously to study the relationship between the WNPSH and precipitation ove ther East Asia Monsoon region before the mid-1970s.     

全球越赤道气流的时空变化

本文首先通过850和200毫巴空间、时间剖面图讨论了全球越赤道气流的时空变化。在东半球夏季各月大气低层存在5条越赤道的偏南气流通道,冬季转为偏北气流,呈现了季节性的年变。在西半球,有3条偏南气流和2条偏北气流通道,它们都未呈现出季节性的年变。其次阐述了它们与环流系统的关联。索马里急流的建立与维持,看来与澳大利亚、西太平洋副高和西风的某些先期变化有关系。它们可能说明全球不同地区大气环流系统季节性变化过程存在一定的时间序列。      

Winter mean temperature variability in Turkey associated with the North Atlantic Oscillation

Changes and variability in seasonal average mean and monthly mean winter (DJF) air temperature series at 70 stations of Turkey and the circulation types at 500-hPa geopotential height level were investigated to explain atmospheric controls of temperature variations during the extreme (weak and strong) phases and normal (negative and positive) phases of the North Atlantic Oscillation (i.e., Ponta Delgada–Reykjavik and the Gibraltar–Reykjavik) indices. During the positive phases of the North Atlantic Oscillation indices (NAOIs), northeasterly circulation increased, and thus spatially coherent and significant cold signals dominate over the majority of Turkey. This pattern is closely linked to anomalously low 500-hPa heights over the region of the Icelandic Low, and anomalously high geopotential heights over the regions of the Azores High, the western Mediterranean basin and the Europe, in general including the Balkans and northwest Turkey. Contrarily, during the negative phases of the NAOIs, prevailing westerly winds that originate from the subtropical northeast Atlantic increase, and thus spatially coherent and significant warm signals over the Anatolian peninsula appear. This pattern is closely linked to the increased cyclonic activity and associated increased westerly and southwesterly circulation causing warm maritime air advection over the Mediterranean basin toward Turkey.     

南海高压的强度变异对长江中下游梅雨的影响及有无洪涝预报

用500毫巴月平均高度图,以100—120°E、≥10°N的范围内,≥588位势什米网格点数代表南海高压强度,则6—7月南海高压强度和6—7月长江中下游的梅雨量有较好的相关。由于南海高压强度有一定持续性,因而可根据前期南海高压强弱,预报6—7月长江中下游的梅雨量。用此思路得出的预报公式。能把有无梅雨洪涝反映出来,从1953—1980年,拟合率为28/28,1981—1983年试报也全正确。另外,文内还探讨了用11月环流特征,作下年初夏南海高压的强弱和长江中下游涝梅预报的可行性。      

Regional 500 mb heights and U.S. 1 000-500 mb thickness prior to the radiosonde era

Summary We developed a statistical model relating cyclone track eigenvectors over the U.S., southern Canada, and nearby oceans to a record of mean annual 500 mb heights. The length of the cyclone track record allowed us to calculate mean heights back to 1885. Use of mean annual surface pressure data allowed us to estimate the mean 1 000-500 mb thickness, which was related to mean annual temperature. This temperature calculation is unique in that it cannot suffer from urban or site bias. We find a warming of 1.5°C from the late 19th century to 1955, followed by a drop of 0.7° to 1980. By 1987, the calculated temperatures were 0.3° above the mean for 103 years of record.As an example of regional application, we examine results over the southwestern U.S.With 8 Figures     

Intercomparison of the Summertime Subtropical High from the ERA-40 and NCEP/NCAR Reanalysis over East Eurasia and the western North Pacific

An intercomparison of summertime (JJA) subtropical geopotential heights from the ERA-40 and NCEP/NCAR reanalysis is specifically conducted over East Eurasia and the western North Pacific. The NCEP/NCAR is obviously lower than the ERA-40 in the mid-to-lower troposphere in most regions of East Eurasia before the mid-1970s, but becomes higher than the ERA-40 after the mid-1970s and thus demonstrates stronger increased trends during the period of 1958--2001. Both reanalyses are lower than the observations in most regions of China. The NCEP/NCAR especially shows tremendously systematic lower values before the mid-1960s and displays abrupt changes before the 1970s. Several indices of the western North Pacific subtropical high (WNPSH), calculated from both reanalyzed summer geopotential heights, also reveal that the variation trend of the NCEP/NCAR is stronger than that of the ERA-40 in the mid-to-lower troposphere from 1958 to 2001. Through singular value decomposition (SVD) analysis, the summer geopotential heights at 500 hPa from the ERA-40 are better than the NCEP/NCAR counterparts at interacting with the precipitation over the East Asian monsoon region. The results indicate that the NCEP/NCAR in the mid-and-lower troposphere may overestimate interdecadal changes and should be used cautiously to study the relationship between the WNPSH and precipitation ove ther East Asia Monsoon region before the mid-1970s.     

对中国东部夏季降水有重要影响的一种东亚遥相关型

利用重建的1880-1950年500 hPa高度场资料和1951-2004年的NCEP/NCAR再分析资料,分析了年际尺度上东亚地区夏季大气环流变化特征。结果表明：夏季在东亚沿岸存在一个明显的自北向南的正-负-正环流模态,即鄂霍次克海阻塞高压与副热带高压存在一种同向变化、而它们之间区域的高度场为反向变化的遥相关关系;同时分析了这种大气环流模态与1880-2004年中国东部地区夏季降水的关系。在年际尺度上,正-负-正的环流模态与长江中下游地区和东北的降水有很好的正相关,当夏季的环流处在阻塞高压偏强,且副热带高压偏南偏强、日本及其以东地区上空高度场偏低时,中国长江中下游地区和东北降水偏多。     

对中国东部夏季降水有重要影响的一种东亚遥相关型

 利用重建的1880-1950年500 hPa高度场资料和1951-2004年的NCEP/NCAR再分析资料,分析了年际尺度上东亚地区夏季大气环流变化特征。结果表明：夏季在东亚沿岸存在一个明显的自北向南的正-负-正环流模态,即鄂霍次克海阻塞高压与副热带高压存在一种同向变化、而它们之间区域的高度场为反向变化的遥相关关系;同时分析了这种大气环流模态与1880-2004年中国东部地区夏季降水的关系。在年际尺度上,正-负-正的环流模态与长江中下游地区和东北的降水有很好的正相关,当夏季的环流处在阻塞高压偏强,且副热带高压偏南偏强、日本及其以东地区上空高度场偏低时,中国长江中下游地区和东北降水偏多。     

冬季各月北太平洋涛动的年际变化及其与我国降水异常的联系

利用ERA-Interim的海平面气压(Sea Level Pressure,SLP)再分析资料和中国160站的降水观测资料,分析了冬季各月(当年12月、次年1月和2月)北太平洋涛动(North Pacific Oscillation,NPO)的年际变化特征,及其与我国同期降水异常之间的联系。结果表明:1)冬季各月NPO指数的年际变化较为显著,但各月NPO指数年际变化之间的相关性较差,1979—2012年冬季12月与1月NPO指数年际变化之间的相关系数为0.09,而1月与2月NPO指数的相关系数仅为-0.003,均没有通过信度检验。2)1月和12月NPO指数年际变化与同期我国黄淮流域降水异常之间存在明显的正相关,而2月NPO指数年际变化与同期我国华北降水异常之间为明显的负相关。3)当1月(12月)NPO指数增加1个标准差时,我国黄淮流域降水量比多年平均值增加约50%(40%);而当2月NPO指数增加1个标准差时,我国华北降水量比多年平均值减少约30%。     

1958年8月4—12日西太平洋副热带高压减退过程的研究

本文对1958年8月4—12日中国大陆上西太平洋副热带高压减退过程作了分析。结果指出:它的减退是从200—400毫巴层次中开始,然后向上向下传递,最大变化发生在200毫巴层上,500毫巴以下高度场的变化是很小的,这是由于对流层顶附近的动力因子所决定的。文中还指出,大型环流发展所引起的经圈环流和东风急流显著的变动,是造成高压减退很主要的因素。本文还进一步分析了东风急流减退的物理机制和高压本身结构的演变特点,以及这种变化对高压减退所起的作用。     

北京冷暖冬年环流特征及其与前期北太平洋海温的关系

利用1951～2005年北京气温资料和北半球500 hPa高度及北太平洋海温资料,分析了北京冬季气温的异常变化及其环流特征以及与前期北太平洋海温的关系.20世纪50年代以来北京冬季气温变化具有50、60年代低,自70年代开始逐年代升高的趋势,90年代至今处于高温时期.北京冷暖冬年,其同期和前期500 hPa环流特征具有明显不同;前期北半球副高及有关副高单体其强弱变化,对北京冬季气温有很好的指示性.前期春季西风漂流区海温和南赤道海流区海温异常变化可作为北京冬季异常冷暖的前兆信号.前期春季南赤道海流区海温异常偏高时,有利于北京暖冬年环流形势的形成.前期春季西风漂流区海温异常偏低时,有利于北京冷冬年环流形势的形成.     

西太平洋副热带高压强度和东亚地表热通量的年代际变化特征及关系

利用NCEP/NCAR的月平均再分析资料以及中国国家气候中心的西太平洋副热带高压(副高)强度资料,分析了西太平洋副高强度、500hPa环流场以及东亚地表感热、潜热通量场的年代际变化特征,发现各个季节的西太平洋副高强度及其环流形势均存在一定的年代际变化,变化发生的时间为1978年前后,20世纪70年代中期以后副高强度有所增强。副高强度在季节间的延续性也发生了一定的年代际变化,1978年以后季节间的延续性增强,全时段的延续性受后一时段的影响较大。东亚地表感热、潜热通量场也存在明显的年代际变化,感热通量的变化关键区在大陆上,主要为青藏高原东、西部,其发生年代际变化要早于西太平洋副高强度变化的时间(20世纪60年代中后期),但它们发生差异变化的时间则接近西太平洋副高强度发生年代际变化的时间,在20世纪60年代中后期以前,高原感热通量体现为稳定的西高东低,而20世纪70年代中期以后则转为稳定的东高西低,其中,近10年时间为调整过渡期,因此,它们各自的年代际变化所造成的影响会有所滞后。潜热通量的变化关键区则位于海洋上,主要是西太平洋地区,1978年以前春季地表潜热通量距平为南正北负,之后转为南负北正,而夏季潜热通量距平则...     

东亚对流层上部和平流层中下部大气环流的初步研究

根据1957—1961平东亚九十余个探空站的记录,对东亚对流层中上部和平流层中下部的大气环流特点作了初步的分析,得到如下几点结果: 1.在冬季,对流层中上部的气压场和风场特点和过去研究的结论基本一致。在夏季,高原部分的环流特征却和过去的结论不同,夏季在高原上对流层中部出现微弱的气旋性环流,但在300毫巴已在反气旋的控制之下,而且反气旋的势力愈往上去愈强,在100毫巴处高原上空的反气旋达到最大强度,这是与青藏高原的热力性质有关系的。此外,从1月到7月东亚对流层上部的气压场和风场变化甚大,在中高纬度气压场有相反的趋势,并且副热带高压脊线从冬季的北纬15°位置移到夏季的北纬28°。 2.在东亚沿海,中纬度的几个测站在平流层中部的温度年变程呈双峰型,最高温度出现在1月和6—7月。在低纬度温度的年变程也呈双峰,但位相与中纬度相反。低纬温度年变化特点与辐射有关;中纬度的温度年变化,经过计算表明,1月的高峰与温度平流有密切关系。 3.东亚对流层中上部和平流层中下部风场的季节变化,与对流层中下部一样显著。从夏到冬的环流季节变化过程,高低空有一致性,而从冬到夏的环流季节变化过程,高低空变化并不一致。     

中国东部地区夏季极端高温的特征分析

利用中国东部地区449个气象站的日最高气温资料,应用趋势分析法等,分析了1960-2012年夏季极端高温日数、持续高温日数的时空变化特征。分析发现:北方地区、华南地区和杭州湾周围地区两个高温指数都呈现增加趋势,长江与黄河之间的中部地区都减小。而在长江下游南部地区极端高温日数显著增加,但持续高温日数却明显减少。从季节特征上看,淮河以北的地区两个高温指数主要集中在6、7月;而以南的区域主要集中在7、8月。各个地区的这两个高温指数与降水日数均呈现显著的负相关,但南北有明显的差异,北方地区负相关的在年际变率以及5 a尺度都很显著,而中部地区则只在年际尺度上显著。杭州湾与华南地区持续高温日数与降水日数的相关体现在5 a尺度上。北方极端高温的显著增加与该地区降水日数与降水量明显减少密切相关。西北太平洋副热带高压显著的西伸,与东南地区的两个高温指数的变化有关。     

Recent variations in 700 hPa geopotential heights in summer over Europe and the Middle East,and their influence on other Meteorological factors

Summary Recent variations in atmospheric circulation in the eastern Mediterranean are analyzed and discussed. Interdecadal differences in mean monthly 700 hPa geopotential heights for June, July, and August in the period 1951–1980 show a trend of decreasing pressure of the subtropical high pressure belt over the Sahara Desert. The decrease is observed in the magnitude of the high pressure, in its areal extent, and in its northward position. Broader variations in other meteorological variables, such as rainfall regimes, temperature fields, wind variability, and evapotranspiration rates, are discussed in relation to variations in pressure fields and in indices of circulation such as the North Atlantic Oscillation. The trend from the 1950s through the 1970s was towards more temperate summer climate in the region.With 5 Figures     

南疆夏季异常高温的气候背景分析

利用1951-2005年若羌、且末及和田3个代表站55 a气温和北半球500 hPa高度及北太平洋海温资料,分析了南疆地区夏季高温年的气候变化,并对其形成进行海温场背景分析。发现南疆地区夏季高温的形成与北半球大气环流和北太平洋海温异常变化相联系。前期10月和2月相关的北半球副高特征指数对南疆地区夏季温度有很好的指示性;南疆地区夏季高温年发生的前期1月份开始,即在北太平洋建立西南海区高东北海区低的海温距平分布型,这种分布型持续到5月份结束。但这2个海区前期海温的异常变化不同,表现为:1-2月份西南海区海温变化幅度小,东北海区海温变化幅度大。3-5月份则西南海区海温变化幅度大,东北海区海温变化幅度小。