半球月平均位势高度场的若干环流指数及其变化特征

给出了表征半球月平均位势高度场性质的若干环流指数：气候场强度Ic、气候异常场平均强度Ia、气候场不稳定度Ius。用NCEP／NCAR40a再分析月平均位势高度场资料作了计算和分析，结果表明，这些环流指数存在清晰的时空结构和北、南半球差异，它们概括地给出了地球大气位势高度场气候及其异常的基本特点。     

2009/2010年北半球冬季异常低温分析

分析了2009/2010年冬季(2009年12月1日至2010年2月28日,简称09/10年冬季)北半球地面气温异常特征及同期的水平与垂直环流场的异常结构。结果表明地面气温的异常呈现出带状的分布,表现为在低纬度为正异常、中纬度负异常及高纬度正异常的"正负正"的分布特征,最大的降温区在欧亚大陆和美国东部,其中局部的降温超过了-4℃。09/10年冬季北半球中纬度的地面气温相比过去15年冬季的平均值下降了近1℃,而在欧亚大陆的局部地区降温超过了-8℃。水平环流场的异常特征为:海平面气压和位势高度均表现为高纬度正异常而中纬度负异常的"北高南低"的分布特征,与此同时,中纬度出现气旋式的异常环流而高纬出现反气旋式的异常环流,这种分布形势在高低层表现得较为一致。经圈环流异常特征为:费雷尔环流减弱,中纬度出现异常的上升运动而高纬度出现异常的下沉运动,与此同时,中纬度对流层气温降低,而低纬度和高纬度的对流层气温升高,副热带急流增强,而极地急流减弱。09/10年冬季北半球环流的异常特征与北半球环状模(NAM)负位相时的极为相似。对多年冬季北半球地面气温和NAM指数进行合成和相关分析,结果表明当NAM处于正(负)位相时,北半球中纬度地面气温出现正(负)异常带,并且在欧亚大陆和美国东部最为显著,局部升温(降温)的幅度达到2℃。在热带外地区,经向温度平流是控制温度局地变化的关键因子。NAM影响北半球地面气温的物理机制分析表明,NAM主要是通过影响经向温度平流来影响北半球中纬度气温的。当NAM为正位相时,北半球费雷尔环流加强,中纬度带和高纬度带发生大气质量的交换,海平面气压场表现为中纬度异常高压而高纬度异常低压的"南高北低"的分布特征,中纬度地表出现异常的南风,进而经向暖平流加强,最终导致中纬度地面气温升高,NAM负位相年时与之相反。这个结果揭示了NAM作为自然变率对中纬度地面气温的调控作用。     

NCEP/NCAR再分析资料中南北半球大气质量交换的特征研究

采用珠江流域1954～2003年51站的月降水资料,利用主分量分析方法,研究珠江流域4～9月降水的空间分布特征.分析结果表明:珠江流域4～9月平均降水量在600～1 900 mm之间,最大中心在广东阳江附近,自东南向西北逐渐减小;其标准差分布基本上是从东向西减小,最大变率中心仍然在广东阳江附近.珠江流域4～9月降水存在5种主要分布型态:全区涝(旱)型、南涝(旱)北旱(涝)型、东涝(旱)西旱(涝)型、东西涝(旱)中部旱(涝)型、南和北旱(涝)中部涝(旱).珠江流域出现全区性涝(旱)和南旱(涝)北涝(旱)的分布型态较多,占总年数的64%.珠江流域夏半年降水场在1983～1992年呈较显著的全区偏旱分布;在1967～1971年前后东涝西旱的分布较显著;在1979年前后中部涝东西旱分布较明显.在1985～1986年前后有南北部涝中部旱分布特征.南涝北旱和南旱北涝分布交错出现,没有明显的集中分布期.     

近百年北半球陆面降水资料的插补及初步分析

采用ＥＯＦｓ展开方法插补延长了一个北半球陆面月降水资料,并讨论了该资料插补工作的合理性。利用该资料初步分析了近百年北半球陆面降水的基本特点。     

南半球对流层大气对热带太平洋-印度洋海温异常综合模的响应及其机制解释

利用NOAA SST及NCEP/NCAR再分析资料, 研究了热带太平洋—印度洋海温异常综合模和南半球对流层大气之间的遥相关模态并对其进行了机制解释。首先通过相关和合成分析, 给出了遥相关的空间模态, 结果表明: 北半球秋、冬季, 在南半球对流层大气存在和热带太平洋—印度洋海温异常综合模密切联系的遥相关作用中心, 该中心的分布构成一列明显的从赤道中太平洋出发, 最终到达非洲中南部及赤道印度洋的Rossby波列, 将赤道太平洋、印度洋与南半球中高纬度大气连接起来, 起到了类似“大气桥” 的作用。而单纯IOD和单纯ENSO均难以在南半球对流层激发出遥相关波列, 进一步证实了两者共同作用的影响。其次, 利用行星波能量传播理论对两者之间的遥相关进行了机制分析, 发现纬向波数为1～3的大气行星波的能量传播是热带太平洋—印度洋海温异常综合模与南半球对流层大气之间遥相关的一种可能的联系方式。     

Seasonality of the Interaction between Convection over the Western Pacific and General Circulation in the Northern Hemisphere

The seasonality of the interaction between convection over the western Pacific and general circulation in the Northern Hemisphere (NH) is analyzed in the present paper with singular value decomposition (SVD) and empirical orthogonal function (EOF) analysis approaches, based on 500 hPa monthly mean geopotential height data and high-cloud amount data. The analyses demonstrate that coupled dominant patterns in the interaction between the convection over the western Pacific and the general circulation in NH are different in various seasons. In spring, the convection over the western Pacific is closely related with the western Atlantic (WA) and North Pacific (NP) like patterns of the general circulation in NH, and some associations between the WA and NP like pat?terns and the El Ni?o / Southern Oscillation (ENSO) cycle are also existed. The Pacific Japan (PJ) pattern is the dom?inant pattern in the interaction between the interannual variabilities of the convection over the western Pacific and the general circulation in NH summer. The WA like pattern and 3-4 year period oscillation are also relatively obvious for the summer case. In autumn, the convection over the western Pacific is closely linked with the Eurasian (EU) like pattern and the Atlantic oscillation in the general circulation in NH, it is suggested that in autumn the vitiation of convective activity over the western Pacific is largely affected by the general circulation anomaly (cold air from high latitudes) through EU like teleconnection pattern. Abrupt change happened by the end of 1980’s in the autumn interaction. The strong interaction between the western Pacific (WP) and EU like patterns in the general circulation in NH and the convection over the western Pacific and a linear trend of increasing of this interaction are also suggested in winter. It is also demonstrated that the interaction in summer and winter is stronger than in the transition seasons (spring and autumn).     

CLIMATIC ABRUPT CHANGE IN THE NORTHERN HEMISPHERE FOR 1920s AND 1950s

In recent years,a large number of papers on the climatic sudden change have been presented.From the viewpoint ofclimatic sudden change,two methods of studying climatic sudden change are applied in this paper.The Northern Hemi-sphere land temperature(NHLT)during 1851—1984,China temperature(CT)during 1873—1990 and the NorthernHemisphere sea-level pressure(NHSLP)at each grid point during 1899—1987 are analyzed by the moving T-test.Theresults show that there exist two climatic sudden changes in the 1920s and the 1950s during the past 100 years,and thenfeatures of circulation for the two sudden changes are discussed by the NHSLP data.