A diagnostic study of heavy rainfall in karachi due to merging of a mesoscale low and a diffused tropical depression during South Asian summer monsoon   总被引：4，自引：0，他引：4  

Ghulam RASUL  Qamar-uz-Zaman CHAUDHRY  ZHAO Sixiong  ZENG Qingcun  QI Linlin  ZHANG Gaoying 《大气科学进展》2005,22(3):375-391

This paper presents the results of a diagnostic study of a typical case of very heavy rainfall during the South Asian summer monsoon when a mesoscale low in a desert climate merged with a diffused tropical depression. The former low was located over Pakistan‘s desert region and the latter depression originated over the Bay of Bengal. Surface and NCEP reanalysis data supported by satellite and radar images were incorporated in the diagnosis. The relationship between the heavy precipitation process and large-scale circulations such as monsoon trough, subtropical high, westerly jet, low level jet and water vapor transport were investigated to further understand the mechanism of this peculiar interaction. It was found that: (1) the mesoscale low developed as a result of cold air advection aloft from northern latitudes and strong convection over the region of humidity convergence on 24 July 2003 over the lndian Rajistan area. (2) On the same day, a low that formed over the Bay of Bengal was transformed into a monsoon depression and moved westward to the mesoscale low which existed over southwest India and the adjoining southeastern parts of Pakistan. (3) Initially, the mesoscale low received moisture supply from both the Bay of Bengal as well as the Arabian Sea, whereas the Bay of Bengal maintained the continuous supply of moisture to the monsoon depression. (4) After the depression crossed central India, the Bay‘s moisture supply was cut off and the Arabian Sea became the only source of moisture to both the closely located systems. On 27 July, both of the systems merged together and the merger resulted in a heavy downpour in the Karachi metropolitan and in its surroundings. (5) With the intensification as well as the southeastward extensionof the subtropical high and the shift of the monsoon trough axis from southwest-west to northeast-east,the monsoon depression moved southwestward. In this situation, there existed a very favourable condition for a merger of the two systems in the presence of cross-latitude influence. (6) A number of convective cloud clusters were developed and organized in the mesoscale low. Probably, interactions existed among the multi-scale systems.  相似文献   

On board measurement of black carbon aerosols over the Arctic Ocean in summer     

TANG Jie  BIAN Lingen  YAN Peng  LAI Xin  LU Changgui 《极地研究(英文版)》2011,(4):253-259

  相似文献   

“区际联系与区域协调发展、区域经济发展”训练     

贾松柏  鲁爱华 《地理教学》2011,(21):47-52

一、选择题（每小题只有一个正确答案） 下图是“我国某区域沿不同纬度所做的地形剖面组图”。读图回答1～3题。  相似文献   

“地球”冲刺新题专项训练     

陈继革 《地理教学》2011,(3):51-53,21

图1为某时刻全球部分经纬网图,图中相邻两条经线间距相等,AC为部分晨昏线,A是晨昏线纬度最高点,图示时刻地球公转速度在加速,回答1～3题。  相似文献   

高精度磁测正常场改正和高度改正精度     

简燕  李文尧  武中华 《物探与化探》2011,35(3):368-370,387

地球磁场强度存在沿纬度方向和高度方向上的变化,在开展高精度磁测工作时,必须进行高度改正和正常场改正。目前普遍使用的改正方法是根据高斯球谐表达式的13级近似式、十级近似式以及一级近似式进行改正的。经计算发现,与高斯球谐表达式的13级近似式相比,当测点与基点的南北方向距离为30 km时,使用十级近似式计算的正常场改正误差为-0.21 nT;使用一级近似式计算的正常场改正的误差随测点与基点的南北方向距离增大而增大,当测点与基点的南北方向的距离大于4 km时,正常场改正误差大于1 nT;使用一级近似式计算的高度改正的误差随测点与基点高度差增大而增大,当测点与基点高度差大于300 m时,误差大于1 nT。  相似文献   

低磁纬度区△T异常处理解释方法在老挝平然村铜镍多金属矿区的找矿应用     

杨建平 《华北地质》2011,34(2):146-149

老挝华潘省相柯县平然村铜镍多金属矿区处于地球低磁纬度区域,对该区以近似水平磁化为主的△T异常进行化极和向上延拓处理后,再结合地质资料对磁异常进行分析推断解疑,找到了成矿有利地区.经钻探验证,见到了铜镍矿体,取得了找矿突破.  相似文献   

中高纬大气30—60天低频振荡的一种动力学机制   总被引：7，自引：1，他引：7       下载免费PDF全文

杨大升  曹文忠 《大气科学》1995,19(2):209-218

本文着重考虑非均匀基本流的正压局地不稳定性，研究中高纬低频振荡产生的动力机制。基本流是取1980年冬、夏300 hPa的位势场。结果表明正压局地不稳定性能较好地解释中高纬大气30—60 d天振荡。这似乎表明，低频振荡是大尺度大气运动和扰动相互作用的一种固有特征，而不是外源强迫的结果。本文还讨论了适于激发季节内低频振荡的基本流场。初值问题的研究发现中高纬大气30—60 d振荡呈纬向三波模态发展，与初始扰动和基本气流的冬、夏差别无关。  相似文献   

东亚地区森林植被带的三维空间分布   总被引：10，自引：3，他引：10  

方精云 《地理学报》1995,50(2):160-167

东亚森林植被带主要由热带亚热带雨林（季雨林）、暖温带常绿阔叶林、冷温带落中阔叶林和亚寒带针叶林组成。这些植被带的垂直分布高度随纬度（温度梯度）和经度（干湿度梯度）的不同而变化，本文根据大量的地植物学资料，从生态气候学的角度研究了这种变化的规律性并给予了定理的表达。结果表明，在湿润气候区，各森林植被带的分布高度随纬度的增加而下降，下降趋势能用多级正弦函数来表达，随着经度的增加（由内陆向沿海变化），各  相似文献   

以空间直角坐标为参数的子午线弧长计算公式   总被引：2，自引：1，他引：2  

牛卓立 《测绘通报》2001,(11):14-15

以空间直角坐标为参数，推导出了子午线弧长的正反算公式。  相似文献   

高精度重力测量中的纬度效应问题     

李瑞浩 《地震》1989,(6):61-62

我们知道,高精度重力测量中必须顾及弹性地球的潮汐变形对重力场的影响,这种改正一般要采用固体潮理论值乘上潮汐因子δ来实现,它已被人们所熟悉和采用。但是地球在引潮力作用下,两极出现永恒低潮区,赤道附近则出现永恒高潮区。也就是说,弹性地球的潮汐变形存在一个非周期性的系统变化,它是纬度的函数。它满足下面两个等式:  相似文献