一种新的多通道GPS共视资料的处理算法   总被引：2，自引：0，他引：2  

卢晓春  杨旭海  李孝辉  胡永辉 《武汉大学学报(信息科学版)》2003,28(6):736-739

提出了一种按仰角加权的多通道GPS共视资料处理算法，充分利用了所有观测数据，同时抑制了多径等因素影响，从而可提高共视比对精度。对日本邮政省通讯研究所(CRL)和国家授时中心(NTSC)2002年5月～2003年3月的多通道共视比对的处理结果表明，新的处理算法结果更接近真实钟差。  相似文献   

Recent Precipitation Trends in Hungary in the Context of Larger Scale Climatic Changes   总被引：1，自引：0，他引：1  

Domonkos  Peter 《Natural Hazards》2003,29(2):255-271

The time series of monthly precipitation totals from 14 Hungarian observing stations (1901–1998) were analysed to reveal the long term changes in precipitation characteristics occurred in the 20th century. A particular attention was given to the changes in the recent decades and their links with the larger scale climatic and circulation changes over Europe and the Atlantic.The statistical significancesof systematic changes are controlled by linear trend analysis and the Mann–Kendall test. The long term fluctuations are illustrated applying a 15-point Gaussian filter on the time series. The Standardised Precipitation Index is used to evaluate the changes in the drought event frequency. The relationships with larger scale changes are mostly discussed relying on contemporary papers, and the Grosswetterlagen Catalogue is used as well.The annual precipitation total decreased by 15–20% in Hungary during the 20th century. The decline is substantial in both halves of the century, but the precipitation sums in the transition seasons declined in the first 50 years, and the winter precipitation decreased in the latest decades. The precipitation total of the period November–February declined significantly in the last 50 years. In the same time the mean winter value of the North Atlantic Oscillation Index (NAOI) increased, the positions of the main pressure patterns over the Atlantic are shifted northeastward, and lot of other coherent changes detected in the winter climate of the European–Atlantic region. The mean summer precipitation total has hardly changed, but the frequency of summer drought events increased. There are some signs of a shift of the Hungarian summer climate towards a Mediterranean like climate.  相似文献   

Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall     

Yehouda Enzel  Revital Bookman  David Sharon  Haim Gvirtzman  Uri Dayan  Baruch Ziv  Mordechai Stein 《Quaternary Research》2003,60(3):263-273

The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr⁻¹ average isohyet during 1940–1990 are largely synchronous and in phase (70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.  相似文献   

应用区域地基全球定位系统观测分析北京地区大气总水汽量   总被引：30，自引：2，他引：30       下载免费PDF全文

梁丰  李成才  王迎春  毛节泰  方宗义 《大气科学》2003,27(2):236-244

利用2000年6月1日～8月11日北京地区地基全球定位系统(Globe Positioning System)网遥感大气总水汽量试验的观测资料,分析了北京地区夏季大气总水汽量的时空变化,研究了大气总水汽量与日平均温度、地面水汽压和降水的关系.研究结果表明:大气总水汽量存在明显的时空变化,对于地理位置基本相近的台站,海拔高度的影响比较明显,一般情况下高山站的水汽总量低于平原站;在晴天,地面水汽压与大气总水汽量有较好的相关性,而在云雨日,由于高低层大气湿度的变化常常不同步,用地面水汽压估算的大气总水汽量具有较大的偏差;大气总水汽量短时间内的快速增加往往对应有降水过程出现,但总水汽量的大小与降水量之间并没有明显的相关,在降水预报中应综合考虑总水汽量的前期平均水平、短时的增幅和峰值大小等条件的影响.  相似文献   

冬季北极涛动和华北冬季气温变化关系研究   总被引：33，自引：6，他引：33  

何春  何金海 《南京气象学院学报》2003,26(1):1-7

利用北极涛动指数（AOI）、NCEP／NCAR40a再分析资料中的海平面气压（SLP）、850、500、200hPa等压面高度场资料及中国160站月平均气温资料，运用小波分析，经验正交函数（EOF）分析等方法，分析了华北冬季气温和冬季北极涛动指数的变化特征及其关系。结果表明它们之间存在有着显著相关，特别是在年代际尺度上关系尤其密切。华北在20世纪70年代初以前为持续冷冬，80年代中期之后变为持续暖冬，其间相对正常，而冬季北极涛运指数亦存在类似的3个阶段，冬季北极涛动高（低）低数年，华北地区为暖（冷）冬年。其原因在于，北极涛动在于对流层低层和高层都可激发类似EU遥相关型的异常，通过影响西伯利亚高压和东亚大槽影响华北地区气温。强（弱）涛运年大气环流具有弱（强）东亚冬季风特征，西伯利亚高压减弱（增强），亚洲大陆地面东北风减弱（增强），高空东亚大槽减弱（增强）。  相似文献   

2002年北半球大气环流特征及其对中国气候异常的影响   总被引：1，自引：0，他引：1       下载免费PDF全文

艾子 《气象》2003,29(4):24-27

2002年春末夏初一次新的厄尔尼诺事件形成；1～12月北半球大气环流的主要特征表现为：中纬度地区纬向环流盛行，西太平洋副热带高压持续偏强偏西，我国大部地区气温偏高，降水呈南多北少分布；欧亚地区夏季500hPa位势高度距平场上，中高纬从西到东呈现为“ - ”分布形式，贝加尔湖地区为正距平中心，7月在贝加尔湖地区出现典型阻高；东亚夏季风偏强，南亚夏季风及热带对流指数偏弱；夏季赤道辐合带偏弱等。在上述大气环流的影响下，我国的天气气候发生了异常。  相似文献   

南通地区暴雪的天气条件对比分析   总被引：11，自引：0，他引：11  

陈佩君  徐云 《气象》2003,29(12):45-47

通过对20世纪50年代以来南通地区的四次暴雪过程的分析，试从环流形势的配置、强度及物理量场特征上，找出具有共性的暴雪的指标，以供预报参考。  相似文献   

柴达木盆地沙尘暴气候特征及其预报   总被引：3，自引：2，他引：3       下载免费PDF全文

苟日多杰 《气象科技》2003,31(2):84-87

利用1961～2000年柴达木盆地11个气象站的沙尘暴观测资料，分析了柴达木盆地沙尘暴天气的时空分布特征。根据1980～2000年3月至5月的40次沙尘暴天气个例，从高空环流形势、地面冷空气路径、影响因子及其预报指标4个方面进行分析，总结出柴达木盆地春季沙尘暴天气的预报方法。  相似文献   

北京地区大气稳定度垂直分布特征   总被引：7，自引：3，他引：7  

毕雪岩  刘烽  陈辉  吴兑  邓雪娇  黄健 《热带气象学报》2003,19(Z1):173-179

基于北京325米气象铁塔观测资料,分析了北京地区大气稳定度垂直分布特征、日变化特征、季节变化特征.  相似文献   

新疆天山山区大气冰核浓度的测量及分析   总被引：5，自引：0，他引：5  

李艳伟  杜秉玉 《南京气象学院学报》2003,26(3):364-370

利用2001年6、7月份在新疆天山山区两个取样点取得的冰核资料，计算了山区中的冰核浓度，研究了冰核平均浓度日变化、日际变化的规律，并分析了天山山区冰核浓度与一些气象因子的关系及可能原因。得出以下结论：天山山区的大气冰核主要来源于地面土壤，比较缺乏；冰核浓度易受气象因子、地表状况的影响，日变化和日际变化明显．  相似文献