Variability of Convective Activity over the North Indian Ocean and its Associations with Monsoon Rainfall over India     

D. R. Pattanaik 《Pure and Applied Geophysics》2007,164(8-9):1527-1545

The present study is an attempt to examine the variability of convective activity over the north Indian Ocean (Bay of Bengal and Arabian Sea) on interannual and longer time scale and its association with the rainfall activity over the four different homogeneous regions of India (viz., northeast India, northwest India, central India and south peninsular India) during the monsoon season from June to September (JJAS) for the 26 year period (1979 to 2004). The monthly mean Outgoing Long-wave Radiation (OLR) data obtained from National Oceanic and Atmospheric Administration (NOAA) polar orbiting spacecraft are used in this study and the 26-year period has been divided into two periods of 13 years each with period-i from 1979 to 1991 and period -ii from 1992 to 2004. It is ascertained that the convective activity increases over the Arabian Sea and the Bay of Bengal in the recent period (period -ii; 1992 to 2004) compared to that of the former period (period -i; 1979 to 1991) during JJAS and is associated with a significantly increasing trend (at 95% level) of convective activity over the north Bay of Bengal (NBAY). On a monthly scale, July and August also show increase in convective activity over the Arabian Sea and the Bay of Bengal during the recent period and this is associated with slight changes in the monsoon activity cycle over India. The increase in convective activity particularly over the Arabian Sea during the recent period of June is basically associated with about three days early onset of the monsoon over Delhi and relatively faster progress of the monsoon northward from the southern tip of India. Over the homogeneous regions of India the correlation coefficient (CC) of OLR anomalies over the south Arabian Sea (SARA) is highly significant with the rainfall over central India, south peninsular India and northwest India, and for the north Arabian Sea (NARA), it is significant with northwest India rainfall and south peninsular rainfall. Similarly, the OLR anomalies over the south Bay of Bengal (SBAY) have significant CC with northwest India and south peninsular rainfall, whereas the most active convective region of the NBAY is not significantly correlated with rainfall over India. It is also found that the region over northeastern parts of India and its surroundings has a negative correlation with the OLR anomalies over the NARA and is associated with an anomalous sinking (rising) motion over the northeastern parts of India during the years of increase (decrease) of convective activity over the NARA.  相似文献   

Shear waves at a corrugated interface between anisotropic elastic and visco-elastic solid half-spaces     

S. K. Tomar  Jatinder Kaur 《Journal of Seismology》2007,11(3):235-258

Rayleigh’s method of approximation is employed to find out the reflection and transmission coefficients due to an incident plane SH wave at a corrugated interface between a laterally and vertically inhomogeneous anisotropic elastic solid half-space and a laterally and vertically inhomogeneous isotropic visco-elastic solid half-space. The lateral and vertical inhomogeneities are described by the exponential variations of elastic parameters. The formulae of reflection and transmission coefficients are derived in closed form for the first-order approximation of the corrugation. The effects of the corrugation of the interface, the inhomogeneity, the anisotropy, the visco-elasticity and the frequency of the incident wave on these coefficients are studied analytically and numerically for a specific model containing a periodic interface. The results of earlier workers have been reduced as particular cases from the present formulation.  相似文献   

南海夏季风爆发日期和强度的短期气候预测方法研究   总被引：7，自引：1，他引：7  

何敏  许力  宋文玲 《气象》2002,28(10):9-14

利用合成及相关统计方法，研究冬季南海季风指数与850hPa风场、500hPa高度、海表温度、OLR等环境场的相互关系及其影响南海夏季风活动的可能机制。指出冬季南海季风指数及环境场的异常特征可以作为预测南海夏季风活动的前兆信号。在此基础上建立了预测南海夏季风爆发日期和强度的概念模型，1998－2001年的预测试验取得了较好成绩。  相似文献   

黄河上游云凝结核观测研究   总被引：13，自引：1，他引：13  

黄庚  李淑日  德力格尔  李仑格  王黎俊 《气象》2002,28(10):45-49

分析了2001、2001年8月在黄河上游的玛曲－河南县利用美国Mee公司的130型云凝结核计数器观测的资料，讨论了凝结核的谱型，浓度随饱和度、天气状况及一些气象要素变化的关系，通过与其它地方观测结果的比较，可以看出在地表植被较好的黄河上游牧区，人类活动、污染较少，其自然凝结核少，浓度与青岛的测值相近，与海洋过饱和核谱型接近。  相似文献   

平坦地区转换GPS高程的混合转换方法   总被引：48，自引：0，他引：48  

胡伍生  华锡生  张志伟 《测绘学报》2002,31(2):128-133

简要介绍了转换GPS高程的二次曲面拟合法和神经网络方法。然而 ,这 2种方法都有缺点 ,介绍的CF&NNM方法充分利用了 2者的优点 ,通过 2个平坦地区的工程实例 ,证实该方法的有效性 ,并得到一些有工程应用价值的结论。  相似文献   

利用精密星历进行单点定位的数学模型和初步分析   总被引：14，自引：1，他引：14  

陈义 《测绘学报》2002,31(Z1):31-33

精密单点定位(Precise Point Positioning,简称PPP),是相对于一般的单点定位而言的,它是利用GPS的精密星历和钟差文件,以载波相位和伪距为观测资料,进行独立的单点精密定位.它的特点在于各站的解算相互独立,计算量远远小于一般的相对定位.尝试以伪距为观测值,利用JPL给出的精密星历(*.sp3)和钟差(*.clk),进行精密单点定位的试验,取得了初步的结果.  相似文献   

基于COM技术的地图符号库结构设计与实现   总被引：20，自引：1，他引：20  

王伟  张波  殷赣华  范业稳 《武汉大学学报(信息科学版)》2002,27(3):296-300

从符号库的结核设计入手，提出了一种新的符号库模型－双层地图符号库模型。该模型在速度，质量上继承了其他模型的优点。利用COM技术实现了地图符号库设计系统，该系统在符号库的易挂接性和符号的可扩展性上有了很大的提高。  相似文献   

地理空间数据共享机制研究   总被引：7，自引：0，他引：7  

宋国民  贾奋励 《测绘学院学报》2002,19(2):134-136

地理空间数据是地理信息系统的重要组成部分，是国家空间数据基础设施建设的主体，但地理空间数据的多样性导致了数据共享的困难。文中探讨了产生地理空间数据多样性的原因，分析总结了现有的地理空间数据共享的解决方案，并对地理空间数据共享的发展方向进行了展望。  相似文献   

测量监理工作的初步探讨   总被引：3，自引：1，他引：3  

李卫锋  周克勤 《北京测绘》2002,(1):26-28

本文介绍了测量监理工作的主要内容、方法，对道路、桥涵、隧道等工程测量监理工作要点进行了初步探讨。  相似文献   

再论拟准检定法的原理、实施和应用   总被引：2，自引：0，他引：2  

欧吉坤 《测绘工程》2002,11(4):3-6

综合阐述了拟准检定法的原理和特点、研究思路。拟准检定法的关键是如何正确选择拟准观测，文章介绍了初选的复选拟准观测的实施要点。列举了拟准检定法在图相关情况下的相差检测，形变分析中的异常探测以及GPS相位观测的周跳检测和修复等方面的应用例子。  相似文献