1986年冬季热带西太平洋区域性大气总能量收支

本文采用中美海-气合作考察第一次航程(1986.1.9—15,2.1—14)和若干站点的海洋气象资料,计算了热带西太平洋不同区域的大气湿静力能量的水平输送和局地变化、大气非绝热加热诸分量以及各区域海面与大气的热交换项。分析指出,在考察期间热带西太平洋上空,西部区是大气能量水平输送的能汇区,而东、中部区则反之。同时,热带西太平洋上空大气和海洋下垫面是个热源区,尤以西部区最为明显。由此可知,热带西太平洋大气能量收支具有明显的区域性差异,其西部区是较强的大气和海洋下垫面的热源区域,是热量、能量积存最多的地区。     

北太平洋冬季西部发展型天气尺度涡旋对平均流的影响

在中纬度北太平洋大气强斜压区,存在频繁的天气尺度涡旋活动,通过水分、动量和能量输送维持大气环流。为了进一步研究天气尺度涡旋发生发展与大尺度环流之间的联系,利用1981—2013年再分析资料,筛选出西部发展型天气尺度涡旋114个偏强日和87个偏弱日,给出了西部发展型天气尺度涡旋异常导致的动力和热力强迫的变化,同时从能量转换的角度分析了西部发展型天气尺度涡旋与平均流之间的相互作用,并探讨了其与西太平洋遥相关型的关系。结果表明:西部发展型天气尺度涡旋通过动力强迫和热力强迫影响平均流,其中动力强迫主要造成北太平洋中纬度上空的西风气流加速并向北移动;热力强迫的作用则是减弱中纬度大气斜压性。同时,强西部发展型天气尺度涡旋有利于西北太平洋上空对流层低层斜压有效位能向扰动动能的转化增大和扰动动能向平均流的转化增大,有利于中纬度地区对流层高层平均流向扰动动能的转化增大。此外,西部发展型天气尺度涡旋通过与平均流的作用,对维持西太平洋遥相关型的负位相有一定影响。     

西太平洋热带地区大气能量收支分析——中美西太平洋海-气合作考察观测事实之二

依据1986年2月8—14日中美西太平洋海气合作考察资料,计算了西太平洋热带海域(140—160°E,18°N—14°S)内的大气能量收支。结果表明,该区域的能量是由外界向区域内输送的。在东、南、西、西北四个边界积上以能量输到为主,只有在东北边界上,以输出为主。该区内的能量输送是以平均输送为主,扰动输送的数量级较小。考察期间,该区域内大气有明显的增温现象。     

热带西太平洋海面的热量收支——中美西太平洋海-气合作考察观测事实之三

本文根据1986年2月8—14日中国“向阳红14号”考察船以及其它的船泊水文气象观测资料,计算了西太平洋热带海面(140—160°E、18°S—14°N)的能量收支各分量。计算结果表明,这个期间内该海面所获得的热量净收入的大小与赤道辐合带低值系统的增强或减弱有关;海面向大气输送的热量主要是以潜热通量输送方式进行的;考察海域内相当部分海面,供给大气能量大于它从大气接收的能量,其中最明显的地区出现在西太平洋热带地区(10°N附近),而不是在赤道地区。     

中-美联合海气考察期间热带西太平洋的海面热量平衡

根据1986年1—2月中美海气考察船所获得的气象资料和其它海洋气象报告,本文计算了热带西太平洋海面的热量平衡,指出该区域海面供给大气的热量大于它从大气接受到的能量。是一个重要的热源区。同时指出,海洋向大气输送热量最显著的地区是出现在西太平洋西部的热带地区,即在 10°N、130—150°E附近。此外,在该海域内,确定海面热量平衡特性的两个最重要的因素应属潜热通量和太阳辐射通量。      

1987年El Nino后期（9—11月）西太平洋大气静力能的收支

本文利用中科院1987年西太平洋考察资料和中央气象局出版的太平洋、大西洋资料反演出了一套利用温度和高度求算湿度的方法。通过该方法并利用美国国家气象中心的KWBC(5°N×5°S网格点资料)的温度和高度资料,计算了1987年厄尔尼诺期间9—11月西太平洋海域(0—30°N,120—170°E)大气静力能量的变化及其与周围的交换。结果表明,在这个时期,该区域上空大气是强的能源区,区域向周围输出能量。     

夏季黔东南州局地暴雨与西太副高环流的关系

通过对黔东南州1996-2005年夏季发生局地暴雨的主要影响系统、各种物理量场的特征、地形等的综合分析,得出9次局地暴雨都与西太平洋副热带高压位置变化密切相关,西太平洋副热带高压外围的SW气流均增强为急流,并输送大量水汽和不稳定能量,而且特别有利的地形的强化作用,造成黔东南暴雨的落区不同.根据暴雨的不同落区,将其归纳为四种类型,即西部型暴雨、南部型暴雨、中部型暴雨、东部型暴雨.但中、南部型暴雨还有中低层低涡切变线配合产生.     

中国南方春季大尺度大气水汽汇时空变化特征

用1958-2004年NCEP/NCAR再分析资料分析了中国南方春季大尺度大气水汽汇的时空变化特征。结果表明：华南中东部、广西北部-湖南西部-贵州东部地区是中国南方春季水汽汇的两个主要变异中心区。华南中东部春季水汽汇具有明显的年际和年代际变化特征,并以年代际方差占优;广西北部-湖南西部-贵州东部地区春季水汽汇以年际变化为主。华南中东部以及广西北部-湖南西部-贵州东部地区水汽汇的强度异常与东亚上空水汽输送异常导致上述地区垂直积分的水汽通量辐合的异常密切相关,当中国南方上空有西南（东北）风水汽通量距平,即西南风水汽输送增强（减弱）时,则上述地区上空的水汽汇偏强（偏弱）。     

东亚低纬地区局地Hadley环流特征及其与大气臭氧的关系

利用1975—2008年NCEP/NCAR的逐月平均风场资料及1975—2001年ECMWF的逐月多层臭氧质量混合比资料,用大气环流三维分解方法研究了东亚低纬度地区之局地Hadley环流的结构及年代际演变特征,分析了该区域局地Hadley环流异常时对应大气臭氧的空间距平分布。研究结果表明:(1)东亚低纬度地区局地Hadley环流既与纬圈平均Hadley环流具有明显的季节变化,但又具有明显区别于纬圈平均Hadley环流的自身结构特征:除冬季存在明显向南、向北输送的两闭合环流圈外,局地Hadley环流在其余季节均以向南输送为主;(2)该局地Hadley环流具有不同于纬圈平均Hadley环流的年代际演变特征,在整个研究时段上以振荡变化为主,并没有表现出象纬圈平均值那样明显的增强趋势;(3)区域赤道上空平流层20～50 hPa大气臭氧的正负距平异常中包含有局地Hadley环流的异常信息:当局地Hadley环流异常强时,区域赤道上空20～50 hPa大气臭氧有一显著负距平异常中心,反之亦然。     

河西走廊西部干旱区一次极端暴雨天气的水汽特征分析

利用高空、地面观测资料、加密区域站雨量资料、FY-2D云图、NCEP 1°×1°再分析资料,使用物理量诊断、后向轨迹模型等方法分析了 2011年6月15—16日河西走廊西部干旱区一次极端暴雨天气的环流形势、中尺度系统、水汽输送和收支特征。结果表明:河西走廊西部受内蒙古西部到河套地区西北—东南向暖性高压脊西部形成的高原低涡中心影响,200～400 km的低涡中心稳定维持在暴雨区上空超过12 h,形成了良好的动力条件;对流层低层湿度增大气温降低,中层冷空气从低涡南部侵入,大气处于弱不稳定状态,地面风速辐合、地形抬升进一步增强了低涡中心的上升运动,触发局地对流。主要存在随西风气流的西路和绕高原的东路两条水汽输送通道,以绕高原的东路水汽输送为主,其在暴雨期间的贡献率高达84.6%,以对流层中层输入最为显著。甘肃中部500和700 hPa异常偏东气流对东路水汽输送通道的形成十分重要,其能将已到达西北地区东部的暖湿空气继续向西北方向输送从而到达河西走廊西部。暴雨时段内水汽平均净输入强度是前期的2.73倍,对流层中层高原低涡中心、对流层低层风速风向辐合和地形辐合造成暴雨区550、700和800 hPa三层200～400 km的水汽辐合中心,大气可降水量高达34 mm,是夏季平均值的2倍多。     

Impact of atmospheric and oceanic conditions on the frequency and genesis location of tropical cyclones over the western North Pacific in 2004 and 2010

This study examines the impact of atmospheric and oceanic conditions during May–August of 2004 and 2010 on the frequency and genesis location of tropical cyclones over the western North Pacific. Using the WRF model, four numerical experiments were carried out based on different atmospheric conditions and SST forcing. The numerical experiments indicated that changes in atmospheric and oceanic conditions greatly affect tropical cyclone activity, and the roles of atmospheric conditions are slightly greater than oceanic conditions. Specifically, the total number of tropical cyclones was found to be mostly affected by atmospheric conditions, while the distribution of tropical cyclone genesis locations was mainly related to oceanic conditions, especially the distribution of SST. In 2010, a warmer SST occurred west of 140°E, with a colder SST east of 140°E. On the one hand, the easterly flow was enhanced through the effect of the increase in the zonal SST gradient.The strengthened easterly flow led to an anomalous boundary layer divergence over the region to the east of 140°E, which suppressed the formation of tropical cyclones over this region. On the other hand, the colder SST over the region to the east of 140°E led to a colder low-level air temperature, which resulted in decreased CAPE and static instability energy. The decrease in thermodynamic energy restricted the generation of tropical cyclones over the same region.     

北半球冬季大气环流与热带太平洋海表温度二年振荡相互作用的若干事实

本文应用带通滤波统计方法,研究了热带不同地区准二年周期振荡的海表温度与冬季500hPa高度场之间的时滞相关。结果表明,不同热带太平洋地区(西、中、东太平洋)海温对中高纬度大气环流的影响,或严格地说,它们之间的相互影响是不同的。在不同纬圈上,相关系数可以有规则的向东或向西传播。同时在不同径圈上也可以向极地或赤道传播。传播的方向和位置依赖于热带海表温度所在的经度。由于传播的速度十分缓慢,平均约2年80—210个经度,或2年约60个纬度。因此可以认为不属于经典的Rossby波,而是一种新的海气相互作用波。     

1997年北半球大气环流特征及其影响

１９９７年北半球主要环流特征为：５００ｈＰａ西太平洋副热带高压盛夏由弱转强、西伸明显、脊线位置偏北;亚洲中纬度经、纬向环流交替出现,纬向环流盛行,春、秋季经向环流加强,冬、夏季冷空气异常偏弱;盛夏南海季风增强,印度季风偏弱;赤道辐合带偏弱。北半球１００ｈＰａ中低纬度位势高度持续偏高,南亚高压东扩明显;热带海洋出现异常,一次新的厄尔尼诺事件发生,强度大、发展快。在ＥＮＳＯ和大气环流的共同影响下我国天     

The atmospheric heat budget in summer over Asia monsoon area

For better understanding the mechanism of monsoon formation and designing the numerical simulation of the general atmospheric circulation, a new approach of calculating atmospheric radiation is proposed to investigate the distribution of the atmospheric heat source, and the budget of heat component is recalculated. The results show that there is a tremendous atmospheric heat source region over central India, northeast of the Bay of Bengal, east of the South China Sea and about 10 °N at the west Pacific, among which the heating center with a maximum heating rate of 8 ℃/day is located over the Bay of Bengal and the average rate in the Plateau is about 1 ℃/day.     

Observational evidences of Walker circulation change over the last 30 years contrasting with GCM results

In order to examine the changes in Walker circulation over the recent decades, we analyzed the sea surface temperature (SST), deep convective activities, upper tropospheric moistening, sea level pressure (SLP), and effective wind in the boundary layer over the 30-year period of 1979–2008. The analysis showed that the eastern tropical Pacific has undergone cooling while the western Pacific has undergone warming over the past three decades, causing an increase in the east–west SST gradient. It is indicated that the tropical atmosphere should have responded to these SST changes; increased deep convective activities and associated upper tropospheric moistening over the western Pacific ascending region, increased SLP over the eastern Pacific descending region in contrast to decreased SLP over the western Pacific ascending region, and enhanced easterly wind in the boundary layer in response to the SLP change. These variations, recognized from different data sets, occur in tandem with each other, strongly supporting the intensified Walker circulation over the tropical Pacific Ocean. Since the SST trend was attributed to more frequent occurrences of central Pacific-type El Niño in recent decades, it is suggested that the decadal variation of El Niño caused the intensified Walker circulation over the past 30 years. An analysis of current climate models shows that model results deviate greatly from the observed intensified Walker circulation. The uncertainties in the current climate models may be due to the natural variability dominating the forced signal over the tropical Pacific during the last three decades in the twentieth century climate scenario runs by CMIP3 CGCMs.     

全球变化背景下北半球冬季MJO传播的年代际变化

利用1979~2013年实时多要素MJO（Madden-Julian Oscillation）监测（RMM）指数,美国NOAA逐日长波辐射资料和NCEP/NCAR再分析资料等,分析了全球变化背景下北半球冬季MJO传播的年代际变化特征。从全球平均气温快速增暖期（1985~1997）到变暖趋缓期（2000~2012）,MJO 2~4位相频次减少,5~7位相频次增多,即MJO对流活跃区在热带印度洋地区停留时间缩短、传播速度加快,而在热带西太平洋停留时间加长、传播明显减缓。进一步分析发现,以上MJO的年代际变化特征与全球变化年代际波动有关。当太平洋年代际涛动（PDO）处于负位相时,全球变暖趋缓,热带东印度洋—西太平洋海温异常偏暖,使其上空对流加强,垂直上升运动加强,对流层低层辐合,大气中的水汽含量增多,该区域的湿静力能（MSE）为正异常。当MJO对流活跃区位于热带印度洋地区时,MJO异常环流对季节平均MSE的输送在强对流中心东侧为正、西侧为负,有利于东侧MSE扰动增加,使得MJO对流扰动东移加快;而当MJO对流活跃区在热带西太平洋地区,MJO异常环流对平均MSE的输送形成东负西正的形势,东侧MSE扰动减小,不利于MJO快速东传。因此,全球变化背景下PDO引起的大气中水汽含量及MSE的变化可能是MJO传播年代际变化的重要原因。     

Synoptic aspects of the catastrophic flood formation in the northeast of Australia during extreme La Niña 2010–2011

A synoptic mechanism of the formation of atmospheric circulation anomalies over the tropics of the Indian and Pacific oceans observed during the La Niña 2010–2011 culmination is considered using the daily data of the NCEP/NCAR reanalysis. It was established that the most destructive flood during the whole modern history of Australia was caused by the unprecedented activity of the tropical cyclogenesis in the circulation system of the Australian summer monsoon. The tropical cyclones affected in turn the monsoon regions of Australia both from the Indian Ocean through the system of the equatorial zone of westerlies and from the Pacific Ocean through the system of the eastern trade wind. The Pacific trade wind during the Australian flood was maximally developed and the South Pacific high was shifted considerably from the coast of Peru and Chile to the center of the ocean. It is demonstrated that the maximum values of negative SST anomalies were observed not in the east of the Pacific Ocean as in the case of the “canonical” La Niña but they were shifted significantly to the west to the line of the date change. All this enables to refer the extreme La Niña 2010–2011 to La Niña of Modoki type.     

Association between Tropical Convection and Boreal Wintertime Extratropical Circulation in 1982／83 and 1988／89

Boreal wintertime extratropical circulation is studied in relation to the tropical convection during the 1982/83 El Nino and 1988/89 La Nina. The anomaly structure of 1982/83 and 1988/89 over the extratropics reveals remarkably different features as the longitudinal tropical forcing region changes. The Rossby wave source (Positive) shows the largest maximum over East Asia in both years due to the persistent heating from the western Pacific warm pool area. However, the sink term shows contrasting features over the subtropics and extratropics between the two years. In the El Nino year, enhanced tropical convection over the eastern Pacific produces the Rossby wave sink at 10?N and shifted eastward over the North Pacific, while in the La Nina year, the sink area is shifted westward over the North Pacific. The contrasting features between the two events in mean-eddy interaction appears especially over the downstream area of the East Asian Jet. The extension (retraction) of the meanflow eastward (westward) to