环渤海地区城市化对夏季极端暖夜的影响     

李庆祥  黄嘉佑 《气象学报》2013,71(4):668-676

城市化对人类生活息息相关的一些指标(如夏季极端暖夜等)的影响研究尚少.取环渤海地区气象观测站的夏季(6-8月)逐日最低气温资料(1958-2009年),使用广义极值(GEV)分布拟合夏季极端暖夜气温分布,并对拟合函数的3个分布特征参数的年际变化进行分析,根据特征参数变化特征进行城市化对极端暖夜的影响程度的分离.研究结果表明,环渤海地区,在极端暖夜气温分布的3个参数的年际变化中,以位置参数的代表性最好.在城市快速发展时期,城市偏高气温出现的可能性大,但极端气温变化幅度也较大.城市化对环渤海不同类型城市夏季极端暖夜气温的贡献均为上升作用,增温速度最大约为0.3℃/(10a).  相似文献   

Effects of Urbanization on Extreme Warmest Night Temperatures During Summer near Bohai   总被引：1，自引：0，他引：1  

LI Qingxiang  HUANG Jiayou 《Acta Meteorologica Sinica》2013,27(6):808-818

Many previous studies have focused on the impacts of urbanization on regional mean temperatures. Relatively few have analyzed changes in extreme temperatures. Here, we examine the impact of urbanization on extreme warmest night temperatures from 33 stations in the Bohai area between 1958 and 2009. We compute the Generalized Extreme Value（GEV） distribution of extreme warmest night temperatures and analyze long-term variations in its characteristic parameters. A new classification method based on the factor analysis of changes in extreme night temperatures is developed to detect the efects of urbanization in diferent cities. Of the three parameters that characterize the GEV distribution, the position parameter is the most representative of long-term changes in extreme warmest night temperatures. During the period of rapid urbanization（i.e., after 1978）, all three parameters of the GEV distribution are larger for the urban station group than for the reference station group, so are the magnitudes of their variations, and the urban areas have been experiencing higher extreme warmest night temperatures with larger variability. Diferent types of cities in the Bohai area have all experienced an urban heat island efect, with an average urbanization efect of approximately 0.3 per decade.  相似文献   

引发2011年8月宁夏持续高温天气的青藏高压结构分析   总被引：1，自引：0，他引：1  

陈豫英  陈楠  穆建华  朱海斌  何佳 《气象》2013,39(8):988-994

利用常规气象观测资料、中尺度区域自动站逐时地面资料及NCEP/NCAR 1°×1°再分析资料等,对引发2011年8月6-10日宁夏中北部连续5天出现≥35℃的高温天气的青藏高压水平和垂直结构进行了天气学分析.结果表明:青藏高压是一个深厚的暖性负涡度系统,它与西风带长波脊的同位相叠加使得高原上空的长波脊和暖高压稳定加强,受其影响,青藏高压外围586 dagpm线东移越过高原后稳定维持在85°～105°E附近,高压脊线北界伸展到40°～42°N,西北地区大范围长时间处在584 dagpm以上的青藏高压和1000 hPa以下的地面热低压控制区域内;高压上空在中纬度极锋急流的作用下,高原东部存在“高空辐合、低空辐散”的环流配置导致高原东部维持较强的下沉运动,处在下沉区的宁夏上空晴朗少云,湿度小,风力相对较大,地面增温和蒸发强烈,地面感热远远大于潜热,有利于出现以“干热”为主的持续高温天气.在此基础上,文章提出了宁夏夏季高温的概念模型.  相似文献   

影响北京的一例沙尘天气过程的起沙沉降及输送路径分析   总被引：5，自引：1，他引：4  

张亚妮  张碧辉  宗志平  吴英 《气象》2013,39(7):911-922

本文选取2012年4月27-28日影响北京的一次沙尘天气过程进行分析,发现在本次过程中,沙源地区的沙尘暴主要发生在地面冷锋和500 hPa槽后,在近地层强烈的感热加热与中低层冷平流的共同作用下,形成了不稳定层结及深厚的混合层,最高可达600 hPa,是沙尘天气能够影响下游地区的重要条件。本文还通过分析等熵混合层厚度变化及其平流过程来追踪沙尘天气的输送路径和定位沉降地,发现本次过程有两种传输路径,一种是沿辽宁北部向东而后转向东北方向,主要沿等熵混合层平流向下游移动,之后随着等熵混合层的接地沉降到近地层,该路径影响高度较高;另一种是沿辽宁南部向东南方向移动,混合层平流较清楚,但沉降时与东北路径明显不同,在辽东半岛东部地面辐散气流及下沉运动的作用下发生沉降,并随冷锋后冷高压南侧的东风回流向西输送影响北京地区。另外,由于混合层之上的稳定层明显下压,使沙尘输送高度偏低。运用HYSPLIT模式模拟的前、后向轨迹证实了上述两种输送路径,表明北京的扬沙天气是由东风回流造成的。  相似文献   

CHARACTERISTICS OF UT/LS CARBON MONOXIDE INTRASEASONAL OSCILLATIONS AND THEIR IMPACT FACTORS OVER THE TIBETAN PLATEAU AND ITS ADJACENT AREAS IN SUMMER     

陈斌  徐祥德  杨帅  施晓晖  张胜军 《热带气象学报(英文版)》2013,19(2):109-119

The study presented herein investigated the main characteristics of carbon monoxideintraseasonal variability and evaluated its possible impact factors using the upper troposphere and lowerstratosphere (UT/LS) Aura Microwave Limb Sounder (MLS) observations over Tibetan Plateau and itsadjacent areas in summer (June to August) of 2005 and 2006. Observations show a persistent constituentextreme extending up into the UT/LS throughout summer, as well as a temporally reversed phase variationbetween the carbon monoxide and ozone in UT/LS. The intraseasonal oscillations (ISOs) of carbonmonoxide during summer are investigated by using methods of wavelet and band pass filter analysis. It isfound that ISOs over the Tibetan Plateau have periods of 10 to 20 days and 30 to 60 days. The formermainly appeared in upper troposphere while the latter in lower stratosphere. Further analysis shows thatthese two periods of ISOs in UT/LS are mainly in phase to the activities of convection over the south of theplateau and the variation of South Asia High, respectively. The above two factors and their dynamicalcoupling may be responsible for the tracer ISOs at different levels.  相似文献   

VARIATIONS OF CLOUD FRACTION OVER EAST ASIA UNDER GLOBAL WARMING CONDITIONS IN THE PAST 20 YEARS   总被引：1，自引：1，他引：0  

吴涧  刘佳 《热带气象学报(英文版)》2013,19(2):171-180

Based on the variation of cloud fraction revealed by D2 Cloud Climatic Data of the International Satellite Cloud Climatology Project and trend analysis methods, the trend of different types of cloud fraction over East Asia during 1984-2006 is obtained. The analysis focuses on the relationship between temperature and different cloud fraction under the background of globe warming. The result shows a fluctuating decreasing tendency in the total cloud fraction, high-level cloud and low-level cloud over East Asia with the decrement being 2.24%, 1.65% and 1.68%, respectively, while the mid-level cloud increases by 1.07%. In addition, there are great regional differences in cloud fraction. Temperature and water-vapor content variation caused by the greenhouse effects over East Asia is the primary reason for the variation of cloud fraction. Over the Tibetan Plateau, the Bay of Bengal and the Intertropical Convergence Zone, the temperature is negatively correlated with high-level cloud, but positively correlated with mid- and low-level cloud. However, over the West Pacific and the ocean east and north of Japan, the temperature is negatively correlated with low-level cloud but positively correlated with high-level cloud.  相似文献   

青藏高原大地形对华南持续性暴雨影响的数值试验   总被引：2，自引：0，他引：2  

何钰  李国平 《大气科学》2013,37(4):933-944

利用新一代中尺度数值预报模式WRF3.2及NCEP/NCAR 逐日4次1°×1°的FNL再分析资料,通过有、无青藏高原以及将高原高度降低到临界高度的数值试验,研究了青藏高原大地形对我国华南地区2010 年5 月一次持续性暴雨过程的影响。试验结果表明:高原大地形对降水的影响显著,随着高原高度的升高,降水增多,高原以东地区的雨带也由北向南移动;高原地形的机械阻挡作用使迎风坡一侧的近地面层附近为强上升运动,背风坡为下沉运动,并分别对应降水的峰值和谷值区;高原对西风气流的爬流、绕流作用明显,高原升高后爬坡作用减弱,以绕流作用为主;高原的加热作用使气流过高原时南支减弱,北支加强,并加强了高原及其东部地区低层的正涡度和高层的负涡度,使高原上空为强烈的上升运动;高原的热力作用使西太平洋副热带高压位置偏南、偏西并稳定维持;高原大地形对形成稳定的高原季风环流圈有重要作用;高原地形高度的作用有利于定常波的形成,波动中心对应强上升运动,形成降水的大值区,稳定维持的定常波使得降水持续集中在同一地区,造成持续性暴雨。  相似文献   

近30余年来盛夏东亚东南季风和西南季风频率的年代际变化及其与青藏高原积雪的关系   总被引：3，自引：0，他引：3  

程龙  刘海文  周天军  朱玉祥 《大气科学》2013,37(6):1326-1336

利用地面观测资料和NCEP/NCAR再分析资料集,使用相关分析、合成分析等方法,在将地面风分为东南季风和西南季风的基础上,分析了近30余年来盛夏东亚季风频率的年代际变化特征。结果表明:盛夏东南季风、西南季风频率和前期春季青藏高原积雪均在21世纪初期发生了显著的年代际变化;东南季风、西南季风频率由较少改变为较多,春季青藏高原积雪则由深变浅。由于青藏高原积雪厚度发生了年代际变浅,说明青藏高原发生了年代际变暖和南亚高压变强,南亚高压的年代际变强,使得其下游对流层低层(18°~28°N,108°~118°E)的反气旋性环流异常增强,有利于东亚西南季风频率的增加;同时,由于高原发生湿反馈作用,使得淮河地区降水发生年代际变多,由Sverdrup涡度平衡关系,降水的异常增多通过潜热释放,使得东亚副热带高压异常加强,而副热带高压异常变强则有利于盛夏东亚东南季风频率发生年代际增加。  相似文献   

Analytical studies of the cloud droplet spectral dispersion influence on the first indirect aerosol effect   总被引：1，自引：0，他引：1  

解小宁  刘晓东 《大气科学进展》2013,30(5):1313-1319

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Cross-equatorial structures of equatorially trapped nonlinear Rossby waves     

《Dynamics of Atmospheres and Oceans》2013

Analysis of the Sea Surface Height (SSH) from satellite altimeters has shown that equatorially trapped Rossby waves exhibit asymmetric cross-equatorial structures; their northern extrema are much larger in magnitude than their southern counterparts. Such asymmetry is inconsistent with the classical theory for the first baroclinic, first meridional equatorially trapped Rossby mode, which predicts that SSH and zonal velocity are symmetric in latitude and the meridional velocity is latitudinally antisymmetric (Matsuno, 1966). Chelton et al. (2003) attributed the observed asymmetry to the mean-shear-induced modifications of first meridional mode Rossby waves. The present paper examines nonlinear rectification of cross-equatorial wave structures in the presence of different zonal mean currents. Nonlinear traveling Rossby waves embedded in shears are calculated numerically in a 1.5-layer model. Nonlinearity is shown to increase the cross-equatorial asymmetry substantially making the northern extrema even more pronounced. However, nonlinearity only slightly increases the magnitude of the westward phase speed.  相似文献