IMPACT OF ENSO ON THE PRECIPITATION OVER CHINA IN WINTER HALF-YEARS     

李天然  张人禾  温敏 《热带气象学报(英文版)》2015,21(2):161-170

In this paper, the impact of ENSO on the precipitation over China in the winter half-year is investigated diagnostically. The results show that positive precipitation anomalies with statistical significance appear over southern China in El Nio episodes, which are caused by the enhanced warm and humid southwesterlies along the East Asian coast in the lower troposphere. The enhanced southwesterlies transport more water vapor to southern China, and the convergence of water vapor over southern China increases the precipitable water and specific humidity. In La Nia episodes,although atmospheric elements change reversely, they are not statistically significant as those in El Nio periods. The possible physical mechanism of the different impact of ENSO cycle on the precipitation over southern China is investigated by analyzing the intraseasonal oscillations(ISOs) in El Nio and La Nia winter half-years, respectively. By comparing the characteristics of ISOs in El Nio and La Nia, a physical mechanism is proposed to explain the different responses of the precipitation over China to ENSO in the winter half-year. In El Nio episodes, over western North Pacific(WNP) and South China Sea(SCS) the ISOs are inactive and exert little effect on water vapor transport and convergence, inducing positive precipitation anomalies with statistical significance over southern China in El Nio episodes. In La Nia episodes, however, the ISOs are active, which weaken the interannual variation signals of ENSO over WNP and southern China and lead to the insignificance of the interannual signals related to ENSO. Therefore, the different responses of precipitation over China to ENSO in the winter half-year are possibly caused by the difference of intraseasonal oscillations over WNP and SCS between El Nio and La Nia.  相似文献   

Diagnostic analysis of the evolution mechanism for a vortex over the Tibetan Plateau in June 2008   总被引：2，自引：0，他引：2  

李论  张人禾  温敏 《大气科学进展》2011,28(4):797-808

Based on the final analyses data (FNL) of the Global Forecasting System of the NCEP and the obser- vational radiosonde data, the evolution mechanism of an eastward-moving low-level vortex over the Tibetan Plateau in June 2008 was analyzed. The results show that the formation of the vortex was related to the convergence between the northwesterly over the central Tibetan Plateau from the westerly zone and the southerly from the Bay of Bengal at 500 hPa, and also to the divergence associated with the entrance re- gion of the upper westerly jet at 200 hPa. Their dynamic effects were favorable for ascending motion and forming the vortex over the Tibetan Plateau. Furthermore, the effect of the atmospheric heat source (Q1) is discussed based on a transformed potential vorticity (PV) tendency equation. By calculating the PV budgets, we showed that Q1 had a great inffuence on the intensity and moving direction of the vortex. In the developing stage of the vortex, the heating of the vertically integrated Q1 was centered to the east of the vortex center at 500 hPa, increasing PV tendency to the east of the vortex. As a result, the vortex strengthened and moved eastward through the vertically uneven distribution of Q1. In the decaying stage, the horizontally uneven heating of Q1 at 500 hPa weakened the vortex through causing the vortex tubes around the vortex to slant and redistributing the vertical vorticity field.  相似文献   

基于CloudSat资料的冷涡对流云带垂直结构特征   总被引：3，自引：0，他引：3       下载免费PDF全文

钟水新  王东海  张人禾  刘英 《应用气象学报》2011,22(3):257-264

利用CloudSat卫星资料、NCEP再分析资料和FY-2C卫星可见光云图分析了2006年7月20—24日我国东北一次冷涡过程不同时期对流云的垂直结构以及云内中小尺度的结构,发现在冷涡发展阶段的初期,暖锋对流结构表现为孤立的回波系统多,强对流深厚,对流系统体现为孤立、深厚的特征。在冷涡发展成熟阶段,回波强度比冷涡发展初期的对流系统有所减弱,且为浅薄的对流系统。冷涡系统影响下发展的锢囚锋回波系统顶部呈现独特的结构特征:东南部为干冷空气侵入造成的回波区, 中部为锢囚锋主体对流区, 西北部为暖锋遇冷锋抬升作用形成的回波区。在锢囚锋尾部存在冰水含量与液态水含量分层现象,干冷空气侵入层在5 km高度左右,在干冷空气侵入层上部为冰水含量分布的弱回波区,下部为液态水分布的弱回波区。在冷涡成熟阶段,对流系统分布在冷涡外沿,表现为孤立的对流系统,冰水含量多的对流系统主要在冷涡的北面,而液态水主要分布在冷涡中心零度层以下。  相似文献   

安徽淮河流域洪涝灾害防灾减灾能力评估   总被引：13，自引：3，他引：10  

黄大鹏  郑伟  张人禾  霍治国  李加林  彭顺风 《地理研究》2011,30(3):523-530

采用层次分析法并融合专家意见,遵循客观性、数据获取便利性、指标量化可行性并突出主导因素等原则,构建综合防洪除涝能力、监测预警能力、抢险救灾与恢复重建能力以及灾害管理能力的洪涝灾害防灾减灾能力综合评估指标体系,对安徽淮河流域各县市洪涝灾害防灾减灾能力进行评估.评估表明:蚌埠市防灾减灾能力最高,其次为难南市、淮北市,再次为...  相似文献   

Kinematic features of a bow echo in southern China observed with doppler radar     

彭新东  张人禾  王红艳 《大气科学进展》2013,30(6):1535-1548

A bow echo is a type of mesoscale convective phenomenon that often induces extreme weather and appears with strong reflectivity on radar images. A strong bow echo that developed from a supercell was observed over Foshan City in southern China on 17 April 2011. The intense gusty winds and showers caused huge losses of property and severely affected human lives. This paper presents an analysis of this strong meso- n-scale convective system based on Doppler radar observations. The isolated bow echo exhibited a horizontal scale of about 80 km in terms of reflectivity above 40 dBZ, and a life span of 8 hours. The system originated from the merging of a couple of weakly organized cells in a shear line, and developed into an arch shape as it moved through the shear zone. Sufficient surface moisture supply ensured the convective instability and development of the bow echo. The low-altitude winds retrieved from single Doppler radar observations showed an obvious rear-inflow jet along the notch area. Different from the conventional definition, no book- end anticyclone was observed throughout the life cycle. Very strong slantwise updrafts and downdrafts were recognizable from the retrieved winds, even though the spatial scale of the bow echo was small. Strong winds and induced damage on the surface are considered to have been caused by the mid-level rear-inflow jet and intense convective downdrafts.  相似文献   

中国科学院“八五”重大应用项目“灾害性气候的预测及其对农业年景和水资源调配的影响”1993年年会在湖南省召开     

张人禾 《大气科学》1994,(2)

中国科学院“八五”重大应用项目“灾害性气候的预测及其对农业年景和水资源调配的影响”1993年度学术年会，于1993年10月对日－26日在湖南省大庸市索溪峪召开。参加会议的有该项目顾问、中国科学院学部委员陶诗言，特邀代表王绍武教授，承担本项目的研究人员，有关部门负责人等共计95人。这次会议共收到学术论文摘要96篇，其中40篇论文在大会上作了交流。这些论文基本上反映了项目下属的5个课题所得到的研究成果。在第一课题的研究中，确定了研制“中国气候灾害图集”的方案，并完成了三年（1978、1979、1980）的样图初稿，对我国七种气候…  相似文献   

简单热带海气耦合模式中的耦合波及其不稳定性（Ⅰ）   总被引：3，自引：3，他引：3       下载免费PDF全文

张人禾 《大气科学》1995,19(4):455-464

西文建立了一处简单的热带海气耦合模式，模式大气和海洋中含了Ｋｅｌｉｖｎ波和长Ｒｏｓｓｂｙ波。在赤道β平面近似下，讨论了取耦合系统中最大径向模时，即大气和海洋中只存在Ｋｅｌｉｎ波时耦合波的性质。结果指出，向东传的耦合Ｋｅｌｖｉｎ波可以出现不稳定性，并且由于海气相互作用，在长波部分可以产生向西传的耦合Ｋｅｌｖｉｎ波。耦合Ｋｅｌｖｉｎ波的性质与模式中所选用的参数有很大关系，当大气与海洋中自由波的频率相差  相似文献   

ENSO动力学与预测   总被引：10，自引：2，他引：10       下载免费PDF全文

张人禾  周广庆  巢纪平 《大气科学》2003,27(4):674-688

发生在热带太平洋地区的ENSO现象是海气相互作用的集中表现,是年际气候变化中的最强信号.由于它的发生会在全球许多地区引起严重的气候异常,极大地影响着这些地区的工农业生产和人民生活,因此,对ENSO的机理及其预测的研究一直是大气海洋界的一个热点研究课题.中国科学院大气物理研究所在ENSO的机理及其预测等方面进行了大量的研究,取得了许多研究成果.作者将对中国科学院大气物理研究所在这方面的一些研究成果进行回顾和介绍.  相似文献   

热带海气相互作用波及其不稳定性   总被引：8，自引：1，他引：8  

巢纪平  张人禾 《气象学报》1990,48(1):46-54

本文利用一个简单的海气耦合模式,讨论了热带海洋和大气中Rossby波的相互作用。结果指出,海洋和大气中向西传播的Rossby波耦合后,不仅存在着向西传播的波动,而且还可以产生一类向东传的新波。这种向东传播的波动出现在波长较长的波段范围内,这个范围的大小受海气相互作用强度的制约。另外,波动可以出现不稳定性,向西和向东传的波均有不稳定现象发生,不稳定增长率也受海气相互作用强度的制约。最后,根据所得到的海气相互作用波,对ENSO现象作了一个可能的解释。  相似文献   

利用ARGO资料改进ENSO和我国夏季降水气候预测   总被引：7，自引：2，他引：7       下载免费PDF全文

张人禾殷永红  李清泉刘益民 牛涛 《应用气象学报》2006,17(5):538-547

全球海洋ARGO资料的获取为气候预测的研究提供了前所未有的海洋资料。该文首先利用ARGO资料改进次表层参数化方案后的Zebiak-Cane海洋模式, 与统计大气模式耦合, 建立了热带动力海洋-统计大气耦合模式。通过比较应用和未应用ARGO资料改进的海洋模式, 进行了耦合模式的长期回报试验。结果表明:ARGO资料的应用极大地改善了耦合模式对热带太平洋海面温度异常的预测能力, 提前3个月和6个月的回报结果都有很大的改进, 基本上回报出了Ni?o3.4区海面温度异常的演变特征, 对厄尔尼诺和拉尼娜都能够给出较准确的回报, 回报结果与观测之间的相关性在整个热带太平洋区域明显提高。该文还利用国家气候中心 (NCC) 全球海气耦合模式, 对我国夏季降水进行了个例和多年季度回报模拟试验, 探讨了包含和不包含ARGO观测资料的同化资料作为初始场对我国夏季降水预测的影响, 表明采用带有ARGO观测资料的海洋同化初始场, 回报的我国夏季降水分布形式与观测更一致, 回报结果与观测之间的正相关区域变大, 对我国夏季降水的回报水平比采用没有ARGO观测资料的海洋同化初始场时有明显提高。  相似文献