The Antarctic Oscillation-East Asian Summer Monsoon Connections in NCEP- and ERA-40     

ZHU Yali 《大气科学进展》2009,26(4)

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Variations in the summer monsoon rainbands across eastern China over the past 300 years     

郝志新  郑景云  葛全胜 《大气科学进展》2009,26(4):614-620

Based on reconstructions of precipitation events from the rain and snowfall archives of the Qing Dynasty (1736–1911),the drought/flood index data mainly derived from Chinese local gazettes from 1736–2000, and the observational data gathered since 1951,the spatial patterns of monsoon rainbands are analyzed at different time scales.Findings indicate that monsoon rainfall in northern China and the middle-lower reaches of the Yangtze River have significant inter-annual(e.g.,5–7-yr and 2–4-yr)as well as inter-de...  相似文献   

Improving multimodel weather forecast of monsoon rain over China using FSU superensemble   总被引：3，自引：0，他引：3  

T. N. KRISHNAMURTI  A. D. SAGADEVAN  A. CHAKRABORTY  A. K. MISHRA  A. SIMON 《大气科学进展》2009,26(5):813-839

In this paper we present the current capabilities for numerical weather prediction of precipitation over China using a suite of ten multimodels and our superensemble based forecasts. Our suite of models includes the operational suite selected by NCARs TIGGE archives for the THORPEX Program. These are: ECMWF, UKMO, JMA, NCEP, CMA, CMC, BOM, MF, KMA and the CPTEC models. The superensemble strategy includes a training and a forecasts phase, for these the periods chosen for this study include the months February through September for the years 2007 and 2008. This paper addresses precipitation forecasts for the medium range i.e. Days 1 to 3 and extending out to Day 10 of forecasts using this suite of global models. For training and forecasts validations we have made use of an advanced TRMM satellite based rainfall product. We make use of standard metrics for forecast validations that include the RMS errors, spatial correlations and the equitable threat scores. The results of skill forecasts of precipitation clearly demonstrate that it is possible to obtain higher skills for precipitation forecasts for Days 1 through 3 of forecasts from the use of the multimodel superensemble as compared to the best model of this suite. Between Days 4 to 10 it is possible to have very high skills from the multimodel superensemble for the RMS error of precipitation. Those skills are shown for a global belt and especially over China. Phenomenologically this product was also found very useful for precipitation forecasts for the Onset of the South China Sea monsoon, the life cycle of the mei-yu rains and post typhoon landfall heavy rains and flood events. The higher skills of the multimodel superensemble make it a very useful product for such real time events.  相似文献   

西北太平洋夏季风对中国长江流域夏季降水的影响   总被引：11，自引：5，他引：6  

刘芸芸  丁一汇 《大气科学》2009,33(6):1225-1237

利用1979～2005年NCEP/NCAR的环流场再分析资料和降水资料, 通过对季风期降水、 大气环流、 水汽输送及低频振荡等方面的分析, 分别从时间和空间上分析了西北太平洋夏季风与中国长江流域夏季降水的联系。结果表明:(1) 西北太平洋夏季风与中国长江流域夏季降水存在显著的负相关关系, 在西北太平洋夏季风强盛时, 副热带高压异常偏北, 其西侧的偏南气流异常偏弱, 使得我国长江流域形成低层异常环流及水汽输送的辐散区, 从而造成长江流域夏季降水偏少; 而在西北太平洋夏季风减弱的年份, 西太平洋副高异常偏南偏西, 在长江流域以南地区形成异常偏强的偏南风水汽输送, 使得长江流域成为南、 北距平风的汇合区, 其上空对流活动异常活跃, 非常有利于长江流域的降水。 (2) 东亚局地Hadley垂直环流在强、 弱季风年也显著不同, 在强季风年里, Hadley局地环流异常偏弱, 长江流域上空出现的下沉运动距平, 使得该地区降水减弱, 而弱季风年则正好相反。 (3) 西北太平洋夏季风存在显著的气候平均的大气季节内振荡 (CISO), 在西北太平洋夏季风减弱时期, 长江流域降水同时受到源自热带西北太平洋西传CISO和源自热带印度洋东传CISO的共同影响, 可能造成了某种锁相关系, 从而造成降水偏多; 而在强季风年里长江流域只受由西太平洋西传的CISO的影响, 不容易激发降水。  相似文献   

Influence of monsoon over the warm pool on interannual variation on tropical cyclone activity over the western North Pacific   总被引：5，自引：0，他引：5  

陈光华  黄荣辉 《大气科学进展》2008,25(2):319-328

The relationship between the interannual variation in tropical cyclone （TC） activity over the western North Pacific （WNP） and the thermal state over the warm pool （WP） is examined in this paper. The results show that the subsurface temperature in the WP is well correlated with TC geographical distribution and track type. Their relation is linked by the East Asian monsoon trough. During the warm years, the westward-retreating monsoon trough creates convergence and vorticity fields that are favorable for tropical cyclogenesis in the northwest of the WNP, whereas more TCs concentrating in the southeast result from eastward penetration of the monsoon trough during the cold years. The steering flows at 500 hPa lead to a westward displacement track in the warm years and recurving prevailing track in the cold years.
The two types of distinct processes in the monsoon environment triggering tropical cyclogenesis are hypothesized by composites centered for TC genesis location corresponding to two kinds of thermal states of the WP. During the warm years, low-frequency intraseasonal oscillation is active in the west of the WNP such that eastward-propagating westerlies cluster TC genesis in that region. In contrast, during the cold years, the increased cyclogenesis in the southeast of the WNP is mainly associated with tropical depression type disturbances transiting from equatorially trapped mixed Rossby gravity waves. Both of the processes may be fundamental mechanisms for the inherent interannual variation in TC activity over the WNP.  相似文献   

南海夏季风爆发与热带海洋海温和大气环流异常变化关系的研究   总被引：12，自引：0，他引：12  

陈永利  白学志  赵永平 《气候与环境研究》2000,5(4):388-399

用合成和相关分析方法及SVD技术研究了南海夏季风爆发早、晚年份4～6月季风建立时期季风环流的异常及其与热带太平洋-印度洋海温的关系。结果表明,南海夏季风爆发与热带大气环流和海温变异密切相关。（1）当热带中、东太平洋—印度洋（主要在西南部）及南海海温低（高）,西太平洋—澳洲邻近海域海温高（低）时,南海夏季风爆发早（晚）。不同区域海温对季风的影响有明显的季节差异,印度洋主要为晚春至初夏（4～6月）,南海为5～6月,而热带太平洋从前冬一直持续到夏季。（2）不同的海温异常产生不同的季风环流型,南海夏季风爆发早、晚年大气环流的异常变化基本相反。南海夏季风的活动主要受印度季风环流变化的影响,与前期冬春季西太副高的强弱及位置变化密切相关。西太副高弱时,南海夏季风爆发早;反之,爆发晚。（3）热带太平洋—印度洋海温异常引起季风环流和Walker环流的异常变化可能是影响南海夏季风爆发早、晚的物理过程。  相似文献   

1998年南海夏季风的爆发与大气季节内振荡的活动   总被引：42，自引：1，他引：41  

穆明权  李崇银 《气候与环境研究》2000,5(4):375-387

利用NCEP再分析及TBB资料,系统地研究了1998年南海夏季风爆发与大气季节内振荡活动的关系,结果表明,1998年南海夏季风爆发与南海及其临近地区30～60天低频振荡的发展有着极为密切的关系。南海及临近地区30～60天低频纬向风及低频动能的时间-经（纬）度剖面明显地反映出该地区的大气季节内振荡的加强是由于其临近地区（菲律宾以东）30～60天低频气旋发展及其向西扩展的结果,与孟加拉湾地区低频气旋的活动关系不大;同时,我们也看到了夏季风爆发前后南海地区为850hPa低频动能的大值区,而200hPa上为一弱区,反映了1998年南海夏季风爆发期间该地区大气季节内振荡有上弱下强的垂直分布特征。进一步分析表明,南海及其临近地区大气季节内振荡的活动主要为局地振荡型,夏季风爆发后才有明显的向北传播,成为南海夏季风爆发影响东亚大气环流和天气的重要途径之一。另外,1980和1986年南海地区30～60天低频动能的发展特征与1998年的类似,说明了南海及其临近地区大气季节内振荡的局地振荡特征并不是1998年所特有的,它对南海夏季风爆发有普遍的重要作用。  相似文献   

南海夏季风活动的年际和年代际特征   总被引：41，自引：1，他引：40  

戴念军  谢安  张勇 《气候与环境研究》2000,5(4):363-374

利用NCEP风场资料和候平均向外长波辐射（OLR）资料分析了南海区域低层风场与对流活动的关系,在此基础上,采用南海中南部的纬向风平均值来定义南海夏季风的爆发,确定了长序列（1949～1998）的南海夏季风爆发日期和强度指数,并研究南海夏季风活动的年际和年代际变化特征。结果表明：南海夏季风爆发日期和强度指数呈显著的反相关;50年来的气候趋势是,爆发日期逐渐偏晚,强度指数逐渐减弱。二者都存在着明显的年际和年代际变化,它们在不同阶段上的波动是各种时间尺度振荡叠加的结果,而年代际尺度具有非常重要的作用。东印度洋海温异常在南海夏季风爆发前后,均与南海夏季风强度指数呈显著的反相关。东太平洋海温异常在南海夏季风爆发之前,与强度指数反相关,而爆发之后,与强度指数正相关。这体现了南海夏季风活动与ENSO事件的密切关系。  相似文献   

1998年夏季风爆发前后南海上混合层的特征及成因   总被引：8，自引：1，他引：7  

刘秦玉  贾旭晶  孙即霖  张秀芝 《气候与环境研究》2000,5(4):469-481

利用1998年“南海季风实验（SCSMEX）”南北部两个点的资料,采用J.Launianen和T.Vihma提出的方法,计算了潜热通量、感热通量和风应力,分析了南海上混合层动力、热力特征及其与南海夏季风爆发之间的关系。发现在西南季风爆发前后,南海北部、南部的两个观测点的海洋上混合层温度和深度随时间的变化具有不同的特点：北部混合层温度经历由高到低再变高,混合层深度经历由浅变深再变浅的3个时段;南部混合层温度经历由低到高再变低,混合层深度经历由深变浅再变深的3个时段。这与南海南、北部海面的风和海面热通量具备不同的特征有关。在5～6月南海上混合层动力、热力特征基本受局地风与短波辐射控制,海面潜热和感热的作用较小。在5月份,南海南部观测点海面附近存在浅薄的高盐高密度层,在60m以上的上层海洋内存在着许多高盐高密度核。在1998年“南海季风实验”期间南海南、北部两个观测点都存在较浅薄的障碍层,在西南季风爆发期间,南海北部观测点的障碍层较厚达到20m以上。  相似文献   

Simulations of the impact of orbital forcing and ocean on the Asian summer monsoon during the Holocene   总被引：3，自引：1，他引：2  

Yuefeng Li  Sandy P. Harrison   《Global and Planetary Change》2008,60(3-4):505-522

The importance of orbital forcing and ocean impact on the Asian summer monsoon in the Holocene is investigated by comparing simulations with a fully coupled ocean–atmosphere general circulation model (FOAM) and with the atmospheric component of this model (FSSTAM) forced with prescribed modern sea-surface temperatures (SSTs). The results show: (1) the ocean amplifies the orbitally-induced increase in African monsoon precipitation, makes somewhat increase in southern India and damps the increase over the southeastern China. (2) The ocean could change the spatial distribution and local intensity of the orbitally-induced latitudinal atmospheric oscillation over the southeastern China and the subtropical western Pacific Ocean. (3) The orbital forcing mostly enhances the Asian summer precipitation in the FOAM and FSSTAM simulations. However, the ocean reduces the orbitally-induced summer precipitation and postpones the time of summer monsoon onset over the Asian monsoon region. (4) The orbital forcing considerably enhances the intensity of upper divergence, which is amplified by ocean further, over the eastern hemisphere. But the divergence is weaker in the FOAM simulations than in the FSSTAM simulations when the orbital forcing is fixed. (5) The orbital forcing can enhance the amplitude of precipitation variability over the subtropical Africa, the southeastern China and northwestern China, inversely, reduce it over central India and North China in the FOAM and FSSTAM simulations. The ocean obviously reduces the amplitude of precipitation variability over most of the Asian monsoon regions in the fixed orbital forcing simulations. (6) The areas characterized by increased summer precipitation in the long-term mean are mostly characterized by increased amplitude of short-term variability, whereas regions characterized by decreased precipitation are primarily characterized by decreased amplitude of short-term variability. However, the influences of orbital forcing or dynamical ocean on regional climate depend on the model.  相似文献