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A Statistical Analysis on the Effect of Vertical Wind Shear on Tropical Cyclone Development 总被引：6，自引：1，他引：6 
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下载免费PDF全文 Using tropical cyclone (TC) best track and intensity of the western North Pacific data from the Joint Typhoon Warning Center (JTWC) of the United States and the NCEP/NCAR reanalysis data for the period of 1992-2002, the effects of vertical wind shear on TC intensity are examined. The samples were limited to the westward or northwestward moving TCs between 5°N and 20°N in order to minimize thermodynamic effects. It is found that the effect of vertical wind shear between 200 and 500 hPa on TC intensity change is larger than that of the shear between 500 and 850 hPa, while similar to that of the shear between 200 and 850 hPa. Vertical wind shear may have a threshold value, which tends to decrease as TC intensifies. As the intensifying rate of TC weakens, the average shear increases. The large shear has the obvious trend of inhibiting TC development. The average shear of TC which can develop into typhoon (tropical depression or tropical storm) is below 7 m s-1 (above 8 m s-1). 相似文献
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Effect of The Atmosphere on UVB Radiation Reaching The Earth’s Surface:Dependence on Solar Zenith Angle 下载免费PDF全文
下载免费PDF全文 M.El-Nouby ADAM 《大气和海洋科学快报》2011,(3):139-145
The atmosphere protects humans,plants,animals,and microorganisms from damaging doses of ultraviolet-B(UVB) solar radiation(280-320 nm) because it modifies the UVB reaching the Earth’s surface.This modification is a function of the solar radiation’s path length through the atmosphere and the amount of each attenuator along the path length.The path length is determined by solar zenith angle(SZA).The present work explains the dependence of hemispherical transmittance of UVB on SZA.The database used consists of five years of hourly UVB and global solar radiation measurements.From 2001 to 2005,the South Valley University(SVU) meteorological research station(26.20°N,32.75°E) carried out these measurements on a horizontal surface.In addition,the corresponding extraterrestrial UVB(UVBext) and broadband solar radiation(Gext) were estimated.Consequently,the hemispherical transmittance of UVB(KtUVB) and the hemispherical transmittance of global solar radiation(Kt) were estimated.Furthermore,the UVB redaction due to the atmosphere was evaluated.An analysis of the dependence between KtUVB and SZA at different ranges of Kt was performed.A functional dependence between KtUVB and SZA(KtUVB=-a(SZA)+b) for very narrow Kt-ranges(width of ranges was 0.01) was developed.The results are discussed,and the sensitivity of △KtUVB to △SZA for very narrow Kt-ranges was studied.It was found that the sensitivity of △KtUVB to △SZA slightly increases with increased Kt,which means KtUVB is sensitive to SZA as Kt increases.The maximum correlation(R) between KtUVB and SZA was equal to-0.83 for Kt= 0.76. 相似文献
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Predicting the intensity of tropical cyclones(TCs)is challenging in operational weather prediction systems,partly due to the difficulty in defining the initial vortex.In an attempt to solve this problem,this study investigated the effect of initial vortex intensity correction on the prediction of the intensity of TCs by the operational numerical prediction system GRAPES_TYM(Global and Regional Assimilation and Prediction System_Typhoon Model)of the National Meteorological Center of the China Meteorological Administration.The statistical results based on experiments using data for major TCs in 2018 show that initial vortex intensity correction can reduce the errors in mean intensity for up to 120-h integration,with a noticeable decrease in the negative bias of intensity and a slight increase in the mean track error.The correction leads to an increase in the correlation coefficient of Vmax(maximum wind speed at 10-m height)for the severe typhoon and super typhoon stages.Analyses of the errors in intensity at different stages of intensity(including tropical storms,severe tropical storms,typhoons,severe typhoons,and super typhoons)show that vortex intensity correction has a remarkable positive influence on the prediction of super typhoons from 0 to 120h.Analyses of the errors in intensity for TCs with different initial intensities indicate that initial vortex correction can significantly improve the prediction of intensity from 24 to 96 h for weak TCs(including tropical storms and severe tropical storms at the initial time)and up to 24 h for strong TCs(including severe typhoons and super typhoons at the initial time).The effect of the initial vortex intensity correction is more important for developing TCs than for weakening TCs. 相似文献
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To examine the effect of radar data assimilation and increasing horizontal resolution on the short-term numerical weather prediction, comparative numerical experiments are conducted for a Huabei (North China) torrential rainfall event by using the Advanced Regional Prediction System (ARPS) and ARPS Data Analysis System (ADAS). The experiments use five different horizontal grid spacings, i.e., 18, 15, 9, 6, and 3 km,respectively, under the two different types of analyses: one with radar data, the other without. Results show that, when radar data are not used in the analysis (i.e., only using the conventional observation data), increasing horizontal resolution can improve the short-term prediction of 6 h with better representation of the frontal structure and higher scores of the rainfall prediction, particularly for heavy rain situations. When radar data are assimilated, it significantly improves the rainfall prediction for the first 6 h, especially the locality and intensity of precipitation. Moreover, using radar data in the analysis is more effective in improving the short-term prediction than increasing horizontal resolution of the model alone, which is demonstrated by the fact that by using radar data in the analysis and a coarser resolution of the 18-km grid spacing, the predicted results are as good as that by using a higher resolution of the 3-km grid spacing without radar data. Further study of the results under the radar data assimilation with grid spacing of 18-3 km reveals that the rainfall prediction is more sensitive to the grid spacing in heavy rain situations (more than 40 mm) than in ordinary rain situations (less than 40 mm). When the horizontal grid spacing reduces from 6 to 3 km, there is no obvious improvement to the prediction results. This suggests that there is a limit to how far increasing horizontal resolution can do for the improvement of the prediction. Therefore, an effective approach to improve the short-term numerical prediction is to combine the radar data assimilation with an optimal horizontal resolution. 相似文献
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1.IntroductionInthecompanionPaper(hereafterreferredtoas299),wecombinedthemosaicapproachandtheanalyticaltypeofstatistical--dynamicalapproach,andproPOsedaacombinedapProach",whichcouldrepresentbothinterpatchvariabilityandintrapatchvariabilityaswellascomputationallycostless.Aftertheheterogeneityoftheroughnesslengthic(or/andzeroplanedisplacementheightd,)isconsideredbythecombinedapproachinBiosphere/AtmosphereTransferSchemeVersionie(BATSie)(Dickinsonetal.,1993),expressions,suchasdragcoefficienta… 相似文献
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《中国气象科学研究院年报》2001,(1)
The Study of the Continent Atmospheric Baseline (SCAB) is one of Fundamental Research Projects of the PRC Ministry of Science and Technology. It was formally started at the beginning of 2000. Scientists from the Chinese Academy of Meteorological Sciences, Mt. Wa Liguan GAW/ WMO baseline observatory (Qinghai Province), atmospheric background stations in Lin'an (Zhejiang Province), Shangdianzi (Beijing) and Longfengshan (Heilongjiang Province) participated in the project. The main stipulated tasks are fulfilled, and the final summery report is being prepared. The main advances and achievements in the SCAB are as follows: 相似文献
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《中国气象科学研究院年报》2000,(1)
TheprojectResearchonTechniquesforPreventingAgrometeorologicalDisasters(96-020)wassetupbytheChineseMinistryofScienceandTechnologyduringthe"9thFive-YearPlan.TheprojectwasauthorizedtoputinpracticeinOctober1996.ThechiefscientistsareProfessorXuXiangdeandProfessorWangFutang(ChineseAcademyofMeteorologicalSciences).TheprojectwastakenonjointlybytheChineseMeteorologicalAdministration,theMinistryofWaterResource,theMinistryofForestry,theMinistryofAgricultureandtheChineseAcademyofSciences.Si… 相似文献
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Aerodynamic parameters including the zero-plane displacement (d), roughness length (20), and friction velocity (u*) on the different underlying surfaces of heavy-grazing site, medium-grazing site, light-grazing site, no-grazing site, dune, inter-dune, grassland, rice paddy site, wheat site, soybean site, and maize site have been computed based on the Monin-Obukhov similarity theory by utilizing the micrometeorologically observed data of dune and vegetation in the semi-arid area at Naiman, Inner Mongolia of China, conducted jointly by the Institute of Desert Research, Chinese Academy of Sciences and the National Institute of Agro-Environmental Sciences of Japan in 1990-1994. And their relationships between wind speed and Richardson number are analyzed. The aerodynamic characteristics of different man-made disturbed grassland ecosystems are also compared. Result shows that the vegetation coverage and the above-ground biomass decrease with the increase in man-made stress of the grassland. The roughness length for different underlying surfaces is closely related to vegetation height, above-ground biomass, and ground surface undulation, and Richardson number Ri is also its influencing factor. The friction velocity varies largely on different underlying surfaces, and it is positively proportional to wind speed and roughness length. The aerodynamic parameters of various times on the same underlying surface are different, too. Above results indicate that grassland and vegetation are of significance in preventing desertification, especially in the arid and semi-arid land ecosystems. And the results of this paper are also important for constructing the land surface physical process as well as regional climate model. 相似文献
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1. IntroductionThe adjustment of mass and velocity fields tosome imposed state of imbalance, constitutes a clas-sical problem in meteorology and oceanography. Tak-ing into account of the earth's rotation, the process isusually referred to as 'geostrophic adjustment', and isconcerned with the wind and density fields that persistafter gravity waves have radiated excess energy away(Rossby, 1937), and with the form of the gravity-waveenergy itself. Since the pioneer work of Rossby (1937),the stud… 相似文献
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台风"派比安"分析 总被引：4，自引：1，他引：3
利用1°×1°NCEP/NCAR再分析资料计算了0606号台风“派比安”的物理量场,结合常规气象资料对“派比安”台风的运动路径、长时间大风以及暴雨特点进行诊断分析,结果表明:1台风过程后期华北大槽减弱北收,副高迅速加强西伸,同时“派比安”旋转风结构中始终存在向西北偏西方向偏转的倾向,副高与台风之间的气压梯度增大,引导了“派比安”向偏西北方向移动;2强散度柱与强涡度柱形成耦合机制,促成了强的垂直上升运动,使台风登陆后中心气压填塞缓慢。台风环流没有出现某一部位突然衰减或增强,是造成大风持续时间长的主要原因;3“派比安”生成于热带辐合带中,台风结构对称,登陆后,一直处在小于10m·s-1的风垂直切变环境之中,水汽源源不断的输入台风环流中,是造成暴雨持续时间长、强度大的主要成因。 相似文献
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“西马仑”与“海贝思”台风特大暴雨对比分析 总被引：1，自引：0，他引：1
利用常规气象观测资料、NCEP再分析资料、卫星云图和雷达回波等资料,采用多种物理量诊断分析方法,对路径相似、在闽南地区产生特大暴雨的1308号台风"西马仑"和1407号台风"海贝思"的环流形势特征、云系结构特征及水汽、动力、热力条件进行了对比分析。结果表明:"西马仑"的过程特点是雨强大、降水时间集中,而"海贝思"的特点则是雨强小、降水时间长;"西马仑"云系结构紧密,属中尺度对流云团降水,而"海贝思"云系结构松散,其外围的螺旋云带产生的列车效应是产生特大暴雨的重要原因;两个台风都具有低空急流、风速辐合、低层辐合高层辐散流场等有利于产生特大暴雨的环流形势特征;两个台风都存在低空偏东风和偏南风急流,两支急流为暴雨区提供了充足的水汽条件,低空急流较强的时段与强降水时段相对应;台风中心附近强辐合辐散区的建立和维持是产生特大暴雨重要的动力条件,水汽辐合区的面积和强度与暴雨区范围和降水强度相吻合;垂直速度大值区的维持时间与强降水的维持时间相一致;垂直速度、假相当位温和水汽通量散度的增大和减小,可作为降水增大和减弱的重要依据之一;暴雨区主要落在700 h Pa螺旋度场大值区内,所以螺旋度分析可为台风暴雨落区预报提供参考依据。 相似文献
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热带风暴“北冕”登陆前4小时加强为强热带风暴，并于2002年8月5日06时15分在陆丰沿海地区登陆，从4日08时到8日08时，全市普遍出现了连续性暴雨，市区和普宁降了特大暴雨。本文从热带气旋路径及强度变化、高低层环流、云图演变等几方面对这次强降水过程进行了分析。 相似文献
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利用常规观测资料、地面加密资料、卫星云图资料和雷达资料,对造成济南市"7·18"大暴雨过程的中尺度系统演变情况进行了分析。结果表明,高、低空急流耦合区内中尺度辐合线的形成和维持是造成此次大暴雨的直接原因;济南处于200hPa高空急流出口区的右侧、低空急流出口区的左侧位置正是暴雨、大暴雨产生的关键部位;在减弱的云团右后方不断有新的云团生成,从中-γ尺度发展到中-β尺度,水汽条件充足时发展成中-α尺度,是造成此次大暴雨的主要原因;大暴雨中心与云顶亮温TBB的最低值中心及强度有密切关系;在有利的大尺度背景条件下,带状回波移动的前方不断有新单体生成汇合到主体,使回波增强,降雨增幅,是造成强降水的原因之一。 相似文献
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台湾岛地形对“麦德姆”台风的影响 总被引：2，自引：0，他引：2
采用WRF模式,以2014年10号台风"麦德姆"为例,针对台湾岛中央山脉的局部地形,设计精细化地形试验,数值模拟了"麦德姆"台风登陆台湾岛前后地形对其路径、强度及风雨分布的影响。研究结果表明:真实的地形能更好的模拟和再现"麦德姆"台风发生发展的过程;台湾岛中央山脉地形对登岛"麦德姆"台风的路径有实质性的影响,降低台湾地形高度试验导致台风路径向西南偏转,而提高台湾岛地形高度则导致台风路径向东北偏转,地形高度改变的程度与路径偏转程度成正相关,地形高度改变所导致阻挡效应及台风环流与大尺度环流的相互作用是导致路径偏转的主要原因;台湾岛地形高度的改变对台风强度有明显的影响,增加或减少台湾岛地形高度,都会使台风强度有所减弱,这与地形变化引起的动力狭管效应、云水物质分布及外围云带的对流运动有关;台湾岛地形影响"麦德姆"台风降水的机制更为复杂,其不仅与地形引发的台风强度及结构变化有关,更与地形引起的眼区对流活动和螺旋云带及外围云系的时空分布有关。 相似文献
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1998年7月19日深夜-21日凌晨在川中、东部产生了突发性大暴雨过程,本文在对中尺度雨团、地面中尺度低压系统进行了较深入分析的基础上,利用T106的客观分析场对此过程进行分析,发现:过程发生前后,大气的能量、水汽及辐合上升运动等条件有一个急速突变的过程,致使强降水产生.在这次大暴雨过程中,中尺度特征明显,雨团活动频繁. 相似文献