华南春季温度气候变化研究

利用我国华南3省24个站1951－1995年2－4月的平均气温资料分析该地区春季低温的气候特征，发现有6个严重低温年：1957、1968、1969、1984、1985和1988年。1968年最为严重。严重低温主要发生在3月和4月。福建的低温较频繁，广西的低温较严重。华南春季低温年际变化有明显的阶段性，809年代低温频繁，90年代低温最少，其它年代低温频数大体相当。春季低温和高温年份，亚洲中高纬度大气环流、西太平洋热带高压以及太平洋热带海洋状况都有显著的差异。华南春季低温与亚洲极涡、纬向环流指数、西太平洋副热带高压北界位置及太平洋暖池的海表温度等因子关系密切。     

山东省春季低温冷害特征及其成因分析

利用山东省26个站1961～2002年3～5月的月平均气温资料分析了山东春季低温冷害的气候特征,并从中高纬度环流、太阳黑子和赤道东太平洋海温等方面探讨春季低温冷害的成因。发现有1963,1969,1970,1976,1979,1980,1985和1991年共8个低温冷害年。山东春季气温变化具有明显的阶段性,80年代以前,低温冷害频繁,1991年以后再也没有出现过严重低温年份。春季低温和高温年份,亚洲中高纬度大气环流、太阳黑子活动和赤道东太平洋海温都有显著差异。在低温年,亚洲中高纬度盛行经向环流,太阳黑子相对数明显偏多,其前秋至前冬,赤道东太平洋海温为负距平,且海温逐渐升高,春季为正距平。     

下半年Nino3区海表升温对东亚春季大气环流及山东春季降水的影响

通过分析下半年Nino3区(150o~90oW，5oS~5oN)海表温度(SST)升高引起的次年春季500 hPa高度、850 hPa及200 hPa经向风的异常特征，发现下半年Nino3区显著升温，可导致次年春季热带和西北太平洋副热带地区的500 hPa高度场升高，即西太平洋副热带高压偏强、偏西、偏北，东亚大槽偏弱、偏东；巴尔喀什湖至贝加尔湖的高度场降低，即该地区经常有低槽维持；亚洲至西太平洋地区盛行纬向环流。我国东部沿海地区及邻近海域的偏南风加强，而我国东北和华北地区的偏北风偏弱。这种高度场与风场的异常恰与山东4月降水偏多年所对应的异常特征相吻合，即下半年Nino3区显著升温通过影响次年春季大气环流异常，进而影响山东春季降水。资料统计表明，下半年Nino3区显著升温，次年山东及我国中纬度东部地区春季尤其4月的降水往往偏多。     

广州春季降水的变化及其前兆信号

广州春季降水存在以准2年为主的年际变化和以30年为主的年代际变化，目前处于年代际尺度上的少雨时段。Nino3区的海温异常是广州春季降水最强的前兆信号，它与广州春季降水的显著正相关在前一年的11月份就已出现，并且一直稳定维持到4月份。前冬Nino3区海温异常对广州春季降水的影响是通过影响春季北太平洋副热带高压和低层风场异常实现的。前冬Nino3区海温正异常时，春季副热带高压偏强、位置偏西，华南处于副高边缘垂直运动的上升区，菲律宾以东的低层反气旋环流增加了向华南的水汽输送，从而使得广州春季降水偏多；前冬Nino3区海温负异常时，副热带高压偏弱、位置偏东，华南地区远离副高、处于垂直运动的下沉区，菲律宾以东低层为气旋环流控制，华南地区盛行偏北气流，不利于水汽的向北输送，从而使得广州春季降水偏少，造成春旱。     

1996年南宁地区春播期长低温过程分析

1996年的低温阴雨过程是南宁地区各县均持续9天以上的长低温过程。本文从长低温出现当月的500hPa环流特征及前期环流演变等方面，分析其特点．若对比分析了长低温出现年份（1957、1959、1964、1968、1969年）及编暖年份（1960、1966、1987、1989年）的环流特征及演变规律，得出以下结论：（1）同期环流对比：偏暧年2月欧洲暖性高压偏弱，西太平洋、中国中部、南海高度场为正距平，1996年2月（长低温阴雨年）则相反，欧洲暖快高压们强，南方暖空气势力偏弱，这有利于冷空气大学南侵。（2）前期环流对比：偏轻年三月阿拉斯加、大西洋、欧洲地…     

我国西北地区春季旱涝气候特征研究

利用西北地区160个台站1950～2000年春季降水量资料,讨论了西北5个区域的旱涝气候特征,发现西北东部和北疆山前地带降水气候变化最为激烈,旱涝事件频繁.整个西北地区春季干旱虽较雨涝多见,但严重雨涝的发生多于严重干旱,且严重旱涝的发生自20世纪80年代以来有增加的趋势.西北各区的旱涝演变具有阶段性和群发性的特点,存在年代际的变化周期和5～6年的准周期振荡.西北东部春季严重雨涝和严重干旱发生时,中高纬度大尺度环流及副热带大气环流特征迥然不同,且分别对赤道中东太平洋海温和北太平洋西风漂流区海温异常表现出遥响应的关系.     

前秋雪盖和海温异常对2008年1月南方低温雨雪天气的影响

对1973—2008年1月全国160站的温度和降水资料进行联合EOF分析发现,2008年1月低温雨雪天气与第一模态和第三模态有关,两个模态组合能够解释2008年1月南方地区温度和降水异常的90%以上。与第一模态相关的环流场主要反映了西伯利亚高压偏强且位置偏西,其与前秋中亚-蒙古以北的雪盖面积异常偏大以及北太平洋冷海温异常与关。与第三模态相关环流场则主要反映了副热带高压的增强和南支槽的加深,前秋印度洋暖海温异常有利于次年1月副热带高压增强,而前秋北大西洋和黑潮延伸区暖海温异常与次年1月南支槽的加深有关。      

东北夏季低温冷害气候特征分析

本文利用１９５１年—１９９５年５月—９月平均气温资料分析东北地区６５个测站的夏季低温冷害和严重低温冷害频率,结果表明,低温冷害频率随纬度的增高而增大,严重低温冷害的频率却随纬度的增高而减少。山区的频率要比同纬度的平原地区大。整个东北地区夏季低温冷害的年份从５０年代到９０年代在逐渐减少,各省夏季低温冷害出现的次数大体相当,大约为３年—４年一遇,但出现的年份并不完全相同,东北地区夏季低温与“厄尔尼诺”的关系复杂     

川渝地区夏季高温干旱变化特征及其异常年环流形势分析

分析了川渝地区夏季高温日数时间演变特征及其异常年份的环流形势.结果表明,川渝地区高温日数在20世纪50年代到70年代总体偏多,1979年是由多到少的突变年,80年代高温日数明显偏少,90年代以后又有增多趋势.川渝地区夏季高温酷暑年和凉夏年的环流形势存在着明显的差异.酷暑年,我国南海北部对流增强,使得西太平洋副热带高压偏北,乌拉尔山和鄂霍次克海地区无持续性阻塞高压,同时东亚大槽变浅,青藏高原上升运动减弱.850 hPa距平风场上.川渝地区以南被东北距平风控制,以北被正南距平风控制,这种环流形势配合有利于川渝地区夏季高温干旱的发生、发展.前期春季OLR场变化特征可为川渝地区夏季高温干旱的预测提供一定的参考依据.     

2001年北半球大气环流特征及其对中国气候异常的影响

2001年受前期赤道东太平洋海温长期冷水位相的影响，北半球大气环流的主要特征表现为：500hPa西太平洋副热带高压冬春季偏强，夏季秋偏弱；欧亚地区夏季500hPa位势高度距平场上中高纬从西到东呈现为“－＋－”分布形式，贝加尔湖地区为正距平中心；东亚冬、夏季风偏弱；7月赤道辐合带异常偏强、偏北等。在上述大气环流的影响下，我国的天气气候发生了异常。     

THE CLIMATIC JUMP OF THE WESTERN PACIFIC WARM POOL AND ITS CLIMATIC EFFECTS

1INTRODUCTIONTropicalwesternPacificOceanisanareathathasthehighestoceantemperatureacrosstheglobe.Asmostofthewarmwaterconcentratesintheregion,itisknownasthe搘esternPacificwarmpool?Asshowninsomestudies[1-5],thegeneralcirculationandshort-termclimaticchangeswillbeseriouslyaffectedifthermodynamicconditionchangesinthewaters,whichthenhaveanimportantroletoplayintheonsetofanyENSOepisodes.Therehasnotbeenanyunifieddefinitionoftheindexforthewarmpool.FollowingthecriterionofWyrtki[4],however,theareae…     

青藏高原夏季热力状态和南半球大气环流的可能联系

本文通过对观测和再分析数据采用最大协方差分析以及回归、合成等分析方法,研究了青藏高原夏季地表气温与南半球大气环流之间的遥相关关系。结果表明,前期(4月)南半球极地—中高纬度大气环流呈现负位势高度异常、较低纬度印度洋—西太平洋区域呈现正位势高度异常时,高原中部和东部大部分区域夏季出现暖异常。在上述遥相关中,印度洋—西太平洋海温异常可能起到了重要的中间桥梁作用。在高原夏季温度偏高的年份,前期跨赤道的印度洋—西太平洋海温也持续偏暖,带来的海陆热力对比减小、经向跨赤道气流减弱有利于削弱夏季的季风环流,使得高原夏季降水偏少,有利于形成高原夏季的暖异常。在这一高原气温—南半球大气环流的遥相关关系中,4月南半球的大气位势高度场异常和与印度洋—西太平洋海温异常相关的异常高度场分布也十分相似。这一前期的跨赤道区域海温异常与南半球中高纬度位势高度场异常的因果关系仍有待进一步揭示。     

The regional forcing of Northern hemisphere drought during recent warm tropical west Pacific Ocean La Niña events

Northern Hemisphere circulations differ considerably between individual El Niño-Southern Oscillation events due to internal atmospheric variability and variation in the zonal location of sea surface temperature forcing over the tropical Pacific Ocean. This study examines the similarities between recent Northern Hemisphere droughts associated with La Niña events and anomalously warm tropical west Pacific sea surface temperatures during 1988–1989, 1998–2000, 2007–2008 and 2010–2011 in terms of the hemispheric-scale circulations and the regional forcing of precipitation over North America and Asia during the cold season of November through April. The continental precipitation reductions associated with recent central Pacific La Niña events were most severe over North America, eastern Africa, the Middle East and southwest Asia. High pressure dominated the entire Northern Hemisphere mid-latitudes and weakened and displaced storm tracks northward over North America into central Canada. Regionally over North America and Asia, the position of anomalous circulations within the zonal band of mid-latitude high pressure varied between each La Niña event. Over the northwestern and southeastern United States and southern Asia, the interactions of anomalous circulations resulted in consistent regional temperature advection, which was subsequently balanced by similar precipitation-modifying vertical motions. Over the central and northeastern United States, the spatial variation of anomalous circulations resulted in modest inter-seasonal temperature advection variations, which were balanced by varying vertical motion and precipitation patterns. Over the Middle East and eastern Africa, the divergence of moisture and the advection of dry air due to anomalous circulations enhanced each of the droughts.     

MEAN SQUARE DEVIATION ANALYSIS OF INTERANNUAL SST VARIABILITY IN TROPICAL PACIFIC AND INDIAN OCEAN

Using the SST data series in tropical ocean(20°N-20°S,50°E-80°W)during 1951-1997 to calculate its monthly mean square deviation,the work obtains results showing that interannual SST variability of the Pacific is more significant than that of the Indian Ocean.Especially near the central and eastern equatorial Pacific(165°W-90°W,6°N-6°S）。where it ranges from 2℃ to 4℃.The interannual SST variability is obvious in November and December but small in March and April.The interannual variabiltiy of “warm pool“SST is not so obvious as that of the eastern equatorial Pacific,Howerver,interannual SST variability of the Indian Ocean ranges from 1℃to 2℃ or so,being smaller than that of the Pacific,In the Indian ocean.Interannual SST variability of the Southern Hemisphere is more obvious than that of the Northern Hemisphere,According to above characterstics of interannual SST variability,the key sectors are determined.     

The Southern Oscillation / Northern Oscillation Cycle Associated with Sea Surface Temperature in the Equatorial Pacific

This paper analyzed the time evolution of the global 1000 hPa height anomalies related to the sea surface temperature (SST) in the eastern equatorial Pacific by using ECMWF data in the period 1979-1988, in which two Pacific warm events, 1982/83 and 1986/787, are included. It is found that there are distinct evidences of eastward propagation of alternate positive / negative height anomalies not only in the tropical South Pacific but also in the tropical North Pacific. The former is associated with the Southern Oscillation (SO) and the latter is associated with the so-called Northern Oscillation (NO).It is noteworthy that the alternate positive / negative anomaly centers associated with SO and NO can be traced back to the middle and higher latitudes of the South Indian Ocean and the East Asian continent respectively, which may be significant for the understanding of the causes and mechanism of SO and NO and for the monitoring of ENSO.Furthermore, these evolution processes have a strong symmetry about the     

福建低温阴雨时空分布及异常偏多成因分析

选取1960～2010年福建春播期平均气温资料、日照资料、NCAR/NCEP逐日高度场、风场及逐月海温资料,使用统计方法分析近51a来福建省北部和南部低温阴雨日数的时空分布及异常偏多成因。结果表明:福建省低温阴雨日数的空间分布与福建省的地形及纬度密切相关。近51a来福建低温阴雨日数呈弱减少趋势,福建北部和南部地区年际变化特征相似。未来一段时间福建北部地区低温阴雨日数偏多可能性较大,南部地区低温阴雨日数可能继续偏少。福建低温阴雨日数与乌拉尔山脊强弱、亚洲高纬地区经向环流强弱关系密切。亚洲高纬地区的环流经向度偏强,冷空气不断南下和较强的西南风配合,湿度条件较好,是造成福建低温阴雨日数明显偏多的直接原因。福建北部地区低温阴雨异常偏多年前冬北太平洋(55°N～60°N,155°W～180°W)区域海温明显偏暖;福建南部地区低温阴雨异常偏多年前冬太平洋中东部海域海温明显偏暖。     

ON WESTERLY WIND BURSTS IN EQUATORIAL WESTERN PACIFIC BEFORE AND DURING THE ONSET AND INITIAL DEVELOPMENT PHASES OF ENSO*

By means of NCEP/NCAR reanalysis dataset,the origins of westerly wind anomalies at low level over equatorial western Pacific Ocean before and during the onset and initial development phase of ENSO are explored.Evidences show that westerly anomalies in the equatorial western Pacific(140-180°E) are characterized by two remarkable enhancements in the spring and summer of the year when El Nine emerges.The enhancements are not only.to some extem.due to the eastward propagation of low-level westerlies in equatorial Indian Ocean.but also predominantly resulting from Ihe intense convergence of the meridional wind from both hemispheres.The latitudinal convergence leads to the local intensification of zonal pressure gradient so as to cause the reinforcement and bursts of westerly wind over warm pool.Besides,by virtue of the effect of earth rotation,the northeasterlies(southeasterlies) from the Northern(Southern) Hemisphere turn into northwesterlies(southwesterlies) progressively in the near-equatorial zone.which directly strengthens the westerly velocity.Comparing the contributions of the meridional wind from both hemispheres to westerly wind bursts,is seems that southeasterlies from the Southern Hemisphere are much stronger and more stable than northwesterlies of Northern Hemisphere.It is evident that the southeasterlies to the east of Australia originate from the southern mid-and high latitudes and are in close association with the Southern Oscillation.     

Spatial and interannual variations of spring rainfall over eastern China in association with PDO–ENSO events

The spatio-temporal variations of eastern China spring rainfall are identified via empirical orthogonal function (EOF) analysis of rain-gauge (gridded) precipitation datasets for the period 1958–2013 (1920–2013). The interannual variations of the first two leading EOF modes are linked with the El Niño–Southern Oscillation (ENSO), with this linkage being modulated by the Pacific Decadal Oscillation (PDO). The EOF1 mode, characterized by predominant rainfall anomalies from the Yangtze River to North China (YNC), is more likely associated with out-of-phase PDO–ENSO events [i.e., El Niño during cold PDO (EN_CPDO) and La Niña during warm PDO (LN_WPDO)]. The sea surface temperature anomaly (SSTA) distributions of EN_CPDO (LN_WPDO) events induce a significant anomalous anticyclone (cyclone) over the western North Pacific stretching northward to the Korean Peninsula and southern Japan, resulting in anomalous southwesterlies (northeasterlies) prevailing over eastern China and above-normal (below-normal) rainfall over YNC. In contrast, EOF2 exhibits a dipole pattern with predominantly positive rainfall anomalies over southern China along with negative anomalies over YNC, which is more likely connected to in-phase PDO–ENSO events [i.e., El Niño during warm PDO (EN_WPDO) and La Niña during cold PDO (LN_CPDO)]. EN_WPDO (LN_CPDO) events force a southwest–northeast oriented dipole-like circulation pattern leading to significant anomalous southwesterlies (northeasterlies) and above-normal (below-normal) rainfall over southern China. Numerical experiments with the CAM5 model forced by the SSTA patterns of EN_WPDO and EN_CPDO events reproduce reasonably well the corresponding anomalous atmospheric circulation patterns and spring rainfall modes over eastern China, validating the related mechanisms.     

Delayed impacts of the El Niño episodes in the central Pacific on the summertime climate anomalies of eastern China in 2003 and 2007

In the summers of 2003 and 2007, eastern China suffered similar climate disasters with severe flooding in the Huaihe River valley and heat waves in the southern Yangtze River delta and South China. Using SST data and outgoing longwave radiation (OLR) data from NOAA along with reanalysis data from NCEP/NCAR, the 2002/03 and 2006/07 El Nino episodes in the central Pacific and their delayed impacts on the following early summertime climate anomalies of eastern China were analyzed. The possible physical progresses behaved as follows: Both of the moderate El Nino episodes matured in the central equatorial Pacific during the early winter. The zonal wind anomalies near the sea surface of the west-central equatorial Pacific excited equatorial Kelvin waves propagating eastward and affected the evolution of the El Ni\~no episodes. From spring to early summer, the concurring anomalous easterly winds in the central equatorial Pacific and the end of upwelling Kelvin waves propagating eastward in the western equatorial Pacific, favored the equatorial warm water both of the SST and the subsurface temperature in the western Pacific. These conditions favored the warm state of the western equatorial Pacific in the early summer for both cases of 2003 and 2007. Due to the active convection in the western equatorial Pacific in the early summer and the weak warm SST anomalies in the tropical western Pacific from spring to early summer, the convective activities in the western Pacific warm pool showed the pattern in which the anomalous strong convection only appeared over the southern regions of the tropical western Pacific warm pool, which effects the meridional shift of the western Pacific subtropical high in the summer. The physical progress of the delayed impacts of the El Ni\~no episodes in the central equatorial Pacific and their decaying evolution on the climate anomalies in eastern China were interpreted through the key role of special pattern for the heat convection in the tropical western Pacific warm pool and the response of the western North Pacific anomalous anticyclone.     

前期春季西北太平洋潜热通量与中国南方秋季降水的联系及其可能的物理机制

利用中国科学院海洋研究所提供的印度洋—太平洋海洋热通量资料,研究了1989—2010年中国南方地区秋季降水与前期春季西北太平洋潜热通量年际变化的联系,并讨论了其可能的物理机制。结果表明,前期春季4月西北太平洋(15°—30°N,150°—170°E)潜热通量与中国南方秋季降水有显著的正相关,当前期关键区潜热通量偏高(低)时,则中国南方秋季降水偏多(少)。分析发现前期关键区潜热通量强弱主要由西北太平洋上空气旋性风切变造成,当前期4月关键区潜热通量偏大时,该关键区正处于西北太平洋上空气旋性风切变北侧大风区中,而在其南侧的赤道强西风使得日界线附近出现海温偏高。随后,次表层高海温伴随开尔文波东传,相应地其北侧的低海温伴随罗斯贝波西传,于秋季西传至热带西太平洋地区,并激发出菲律宾反气旋,从而有利于热带洋面暖湿水汽向中国南方输送,使得南方地区降水偏多,反之亦然。