华北产生雷暴大风的动力热力综合指标分析及应用   总被引：1，自引：0，他引：1  

严仕尧  李昀英  齐琳琳  安洁  刘君 《湖北气象》2013,(1):17-23

应用MICAPS重要天气报告数据,筛选出2005-2010年夏季华北地区26次典型雷暴大风过程。选取K指数、对流有效位能、大气可降水量、大风指数、中低层垂直速度、垂直螺旋度、垂直能量螺旋度等7个动力或热力指标,利用NCEP 1°×1°再分析资料计算和统计了槽前型和西北气流型雷暴大风发生时的指标阈值。基于统计结果,进一步设计了指标叠套技术,将其应用于2011年6月华北地区两次不同类型雷暴大风的潜势预报中。结果表明,雷暴大风实际发生区域与指标叠套区域一致性较好,验证了该方法对华北雷暴大风预报的有效性。  相似文献   

云南不同气候带极端气温变化趋势   总被引：3，自引：0，他引：3  

陈艳  段旭  董文杰  郭世昌 《气象科技》2013,41(1):126-130

利用1975-2008年云南6个气候代表站的最高气温、最低气温和平均气温资料,分析了气温序列的变化趋势,探讨了可能的形成原因.结果显示,各代表站的气温总体上呈上升趋势,但气温变化率的大小与其所处的气候带之间没有明显的规律性差异.代表高原气候的香格里拉站其气温增暖趋势最突出,代表北亚热带、中亚热带和南亚热带站点的气温与其有相似的变化趋势,主要表现为最低气温增温速率最大,平均气温次之,最高气温最小,而气温日较差(DTR:Differenceof Temperature Range)有明显减小趋势.温带和北热带代表站气温的变化则有不同的特征,温带的变化表现为最高气温显著上升,最低气温上升速率略小于平均气温的上升速率,DTR变化不显著;北热带的变化表现为平均气温增温速率最大,最低气温次之,最高气温最小,DTR变化不显著.对各站相对暖日、冷日、暖夜、冷夜和霜日的逐年统计分析表明,总体上云南的冷事件在减少,而暖事件增多.  相似文献   

实解析函数在极值点附近的凹凸性     

孙刘平  周展宏 《广东海洋大学学报》2006,26(3):64-67

讨论了一类实解析函数在极小（大）值点附近存在凸（凹）性区间的条件，得到了如下主要结果：若非常值函数y=f（x）在x0处取得极小（大）值，且在x0的某一邻域G内实解析的。则存在x0的一小邻域G^＊包含G，使得原函数在G^＊上为凸（凹）的。  相似文献   

Extreme Earthquake and Earthquake Perceptibility Study in Greece and its Surrounding Area   总被引：3，自引：0，他引：3  

Burton  Paul W.  Qin  Changyuan  Tselentis  G.-Akis  Sokos  Ethimios 《Natural Hazards》2004,32(3):277-312

The sample interval for the selection of extreme magnitudes plays an important part in the quality of Gumbel model fitting. A short sample interval can produce many observations, which is helpful in obtaining a reliably fitting model. However a short sample interval can bring many dummy ``observations', a condition which adversely biases the fitting. The short sample interval also increases the chance to introduce non-independent observations as well, which violates a basic requirement of the Gumbel model. On the other hand, a large time interval not only reduces the number of observations, but also enlarges the observation error. Thus, for Greece, the most suitable parameters of the third Gumbel extreme model are obtained by using a sample interval which produces minimum error. In consideration of the reliability of the seismic data, earthquakes with magnitude M 5.5 in Greece and its surrounding region after 1900 are used mainly in the present paper. In order to obtain well resolved contour maps with smooth changes a 2°× 2° cell with half-degree overlap strategy was used to scan the region. The most expected largest earthquake for the next fifty, one hundred and two hundred years are estimated for each cell. Likewise, the events with magnitude at a probability of 90\% of non-exceedance over the next fifty, one hundred and two hundred years are estimated for each cell. In parallel to this procedure we also analyze the 67 shallow seismic zones outlined by Papazachos and his colleagues and detail individual zone results where these are obtained. The most perceptible earthquake magnitude for the range of intensities I = {VI}, VII and VIII are also calculated. All results show that the areas around the Hellenic Arc and the Cephalonia Transform Fault for Greece have comparatively high frequency of destructive earthquakes accompanied by a high occurrence probability of moderate earthquakes (M 5.5).  相似文献   

试论未来极端气候事件发展趋势的不确定性     

李志忠  刘秀铭  陈秀玲  姜修洋  雷国良  朱芸  靳建辉  胡凡根 《福建地理》2012,(1):12-20

极端气候事件是在一定时间尺度上发生的不同于气候系统平均状态的气候突变.早第三纪的最热事件（PETM）,第四纪中国黄土高原古土壤S4、S5记录的暖湿事件,砂黄土L9、L15记录的干冷事件等都是在轨道时间尺度上发生的极端气候事件.末次冰消期的YD冷事件、全新世9次冷事件是在千—百年尺度上发生的极端气候事件.这些极端气候事件出现于地球气候系统不同的冷暖背景下,它们的成因机制和表现形式有很多不确定性.20世纪以来发生的干旱、洪水、飓风、雪灾、沙尘暴等极端气候事件,无法用持续增加的温室气体的变化来解释.关于极端气候事件发生频率和强度随＂全球变暖＂而增加的结论也存在一定程度的不确定性.因此,简单地将现代极端气候事件统统归因于＂气候变暖＂既不科学也不合理.深入研究各个时间尺度上发生的极端气候事件的波动性、周期性和不确定性特征,有助于科学预测未来气候变化背景下极端气候事件的发展趋势.  相似文献   

近50年来淮河流域极端降水的时空变化及统计特征(英文)     

夏军  佘敦先  张永勇  杜鸿 《地理学报(英文版)》2012,22(2):195-208

Based on the daily precipitation data of 27 meteorological stations from 1960 to 2009 in the Huaihe River Basin, spatio-temporal trend and statistical distribution of extreme precipitation events in this area are analyzed. Annual maximum series (AM) and peak over threshold series (POT) are selected to simulate the probability distribution of extreme precipitation. The results show that positive trend of annual maximum precipitation is detected at most of used stations, only a small number of stations are found to depict a negative trend during the past five decades, and none of the positive or negative trend is significant. The maximum precipitation event almost occurred in the flooding period during the 1960s and 1970s. By the L-moments method, the parameters of three extreme distributions, i.e., Generalized extreme value distribution (GEV), Generalized Pareto distribution (GP) and Gamma distribution are estimated. From the results of goodness of fit test and Kolmogorov-Smirnov (K-S) test, AM series can be better fitted by GEV model and POT series can be better fitted by GP model. By the comparison of the precipitation amounts under different return levels, it can be found that the values obtained from POT series are a little larger than the values from AM series, and they can better simulate the observed values in the Huaihe River Basin.  相似文献   

A Simulation Study on the Extreme Temperature Events of the 20th Century by Using the BCC_AGCM   总被引：3，自引：1，他引：2       下载免费PDF全文

DONG Min  WU Tongwen  WANG Zaizhi  CHENG Yanjie  ZHANG Fang 《Acta Meteorologica Sinica》2012,26(4):489-506

Extreme temperature events are simulated by using the Beijing Climate Center Atmospheric General Circulation Model (BCC AGCM) in this paper. The model has been run for 136 yr with the observed external forcing data including solar insolation, greenhouse gases, and monthly sea surface temperature (SST). The daily maximum and minimum temperatures are simulated by the model, and 16 indices representing various extreme temperature events are calculated based on these two variables. The results show that the maximum of daily maximum temperature (TXX), maximum of daily minimum (TNX), minimum of daily maximum (TXN), minimum of daily minimum (TNN), warm days (TX90p), warm nights (TN90p), summer days (SU25), tropical nights (TR20), and warm spell duration index (WSDI) have increasing trends during the 20th century in most regions of the world, while the cold days (TX10p), cold nights (TN10p), and cold spell duration index (CSDI) have decreasing trends. The probability density function (PDF) of warm/cold days/nights for three periods of 1881-1950, 1951- 1978, and 1979-2003 is examined. It is found that before 1950, the cold day/night has the largest probability, while for the period of 1979-2003, it has the smallest probability. In contrast to the decreasing trend of cold days/nights, the PDF of warm days/nights exhibits an opposite trend. In addition, the frost days (FD) and ice days (ID) have decreasing trends, the growing season has lengthened, and the diurnal temperature range is getting smaller during the 20th century. A comparison of the above extreme temperature indices between the model output and NCEP data (taken as observation) for 1948-2000 indicates that the mean values and the trends of the simulated indices are close to the observations, and overall there is a high correlation between the simulated indices and the observations. But the simulated trends of FD, ID, growing season length, and diurnal temperature range are not consistent with the observations and their correlations are low or even negative. This indicates that the model is incapable to simulate these four indices although it has captured most indices of the extreme temperature events.  相似文献   

“09.4.15”渤海和山东强风过程的动力学诊断分析   总被引：2，自引：0，他引：2  

盛春岩  杨晓霞 《气象》2012,38(3):266-273

2009年4月15日,渤海和山东大部出现了一次强风天气过程。本次过程具有强度大、持续时间短、强风在渤海及山东附近显著加强等特点。为探讨强风的成因,根据常规观测资料以及NCEP分析资料进行了诊断分析。结果表明,本次强风过程是在低层冷锋、高层低涡横槽影响下产生的。冷空气向南推进过程中,冷平流中心由高层向低层传播,850 hPa以下冷平流不断加强,使冷锋不断增强。冷空气到达渤海湾后,锋前的强暖平流与锋后的强冷平流造成低空锋区进一步增强。冷锋次级环流的下沉运动与地面正变压中心对应,变压梯度风与大尺度气压梯度风共同造成强风过程,而强风中的阵风可能与次级环流的强烈脉动有关。  相似文献   

2011年4月17日广东强对流天气过程分析   总被引：6，自引：1，他引：5  

张涛  方翀  朱文剑  章国材  周庆亮 《气象》2012,38(7):814-818

利用地面和高空观测、卫星、雷达和闪电及自动站资料对2011年4月1 7日出现在广东省的强对流天气的背景和演变进行了分析和总结,本次强对流过程出现了短时强降水、雷雨大风和冰雹等强对流天气,具有风力强、中尺度强风暴系统明显、局地性强和灾情严重等特点。分析表明,地面锋面抬升是本次强对流天气发生的主要触发机制,珠三角地区的地形平坦、广东中层的干急流以及较大的垂直风切变可能是强风暴系统发展和维持的主要因素。最后,本文也分析了当时的主观预报思路并提出了一些思考和总结。  相似文献   

北京721特大暴雨极端性分析及思考（二）极端性降水成因初探及思考   总被引：22，自引：10，他引：12  

孙军  谌芸  杨舒楠  代刊  陈涛  姚蓉  徐珺 《气象》2012,38(10):1267-1277

本文是“北京7.21特大暴雨极端性分析及思考”的第二部分,第一部分“观测分析及思考”对此次过程的降水特点、水汽特点、中尺度对流系统（MCS）的环境场条件和发生发展过程进行了分析,指出这是一次极端降水过程。本文进一步从影响降水的因子：降水效率、水汽、上升运动、持续时间等方面进一步探讨极端性降水的成因,所用资料为业务中常用的模式分析和各种观测资料。分析表明,本次过程为典型华北暴雨环流形势,其中高层气流辐散区与低层低涡切变线的耦合是直接诱因;较高的环境相对湿度和湿层较厚,较低的抬升凝结高度和自由对流高度以及热带降水性质提高了本次过程的降水效率;异常大的水汽含量（可降水量达60－80mm）及与其相关的物理量异常,可作为判断极端降水的重要因子;环境大气具有中下层条件性不稳定,上层湿中性层结特性,CAPE值中等,同时上层干侵入增加了对流不稳定,有利于上升运动发展;低涡切变线及华北地形共同触发了MCS的在暖区生成发展;低涡北跳、MCS后向传播特性使暖区MCS东移速度慢,形成“列车效应”,造成降雨持续时间长。本文最后探讨了极端降水的预报思路。  相似文献