PROPAGATION OF 30—60 DAY LOW FREQUENCY OSCILLATIONS AND THEIR INFLUENCE UPON THE SUBTROPICAL WESTERLIES JET STREAM DURING NORTHERN HEMISPHERE WINTER

Based on daily ECMWF gridpoint data of two winters during 1981—1983 including an ENSOyear,propagation of low frequency oscillations(LFO)during Northern Hemisphere winters andtheir influences upon 30—60 day oscillations of the subtropical jet stream are studied with the sta-tistical methods as complex empirical orthogonal function(CEOF)and so on.Results show that inthe winter of a normal year(1981—1982),30—60 day oscillations in the subtropical zone aremainly in the northern and southern flanks of exit region of jet stream.In the ENSO year(1982—1983),they are mainly in the vicinity of entrance and exit regions of jet stream.Intraseasonalchanges of subtropical jet stream manifested themselves as latitudinal fluctuation or longitudinalprogression or regression of about 40 day period.There are marked differences between propagat-ing passages of low frequency modes responsible for changes of subtropical jet stream in the normalyear(1981—1982)and in the ENSO year(1982—1983).Changes of oscillation amplitude showobvious phases.In general,the one in late winter is stronger than that in early winter,strongestone occurs in February.     

A THREE-DIMENSIONAL ELASTIC NESTED-GRID MESO-(β-γ)SCALE ATMOSPHERIC MODEL——PARTI:MODEL DESCRIPTION

A three-dimensional elastic nonhydrostatic mesoscale(β-γ)model with nested-grid is presented.It uses a set of fullequations in terrain-following coordinates as its basic dynamic frame,which is solved with a time-splitting algorithmfor acoustic and gravity waves.The model physical parameterization includes a K-theory subgrid eddy mixing for cloudand free atmosphere,a bulk planetary boundary layer parameterization,and three types of sofisticated cloudmicrophysics schemes with double-parameters for hail-bearing clouds,warm clouds and snowing clouds respectively.The model is designed to be used flexibly for simulations of a variety of meso-and small-scale atmospheric processes,and can be improved as a regional and local operational NWP system in future.     

首都减灾圈的思考与建议

首都减灾圈,系首都减轻自然灾害预测防治圈。1991年12月20—21日在北京召开了《首都圈自然灾害及其减灾对策研讨会》。本文根据这次会议所提供的材料,在从整体上实现减灾的思想指导下,就首都减灾圈的“成灾背景”、“首都减灾圈的组成”、“首都减灾圈的灾害预测与防治状况”、“首都减灾圈的灾害关联性分析”、“首都减灾圈的减灾实效预估”和“首都减灾圈的减灾对策与实施”等六个带有共同性的问题,进行了讨论。供制定首都圈减灾方案时参考。     

贯彻党风廉政建设责任制重在抓落实

近年来,山西省气象局在上级部门的领导下,坚持以邓小平理论、党的基本路线和十五大、十六大精神为指导,认真坚持从严治党方针,按照党风廉政建设和反腐败三项任务一齐抓的工作格局,紧密结合气象部门实际,围绕全省气象工作会议提出的目标任务,以改革创新的精神,坚持标本兼治,狠抓任务落实,加大了从源头上预防和治理腐败的工作力度,取得了党风廉政建设和反腐败斗争的新成效,有力地促进了两个文明建设和各项工作任务的顺利完成。     

秦巴山区降水量分布综合模式

英、德两国都在欧洲；欧洲有４５个国家，面积１０１６万平方千米，７．９亿人口，是世界上发展最平衡、经济最发达、生活质量最高的地方。欧洲的气象现代化程度较高，尤其是英国具有辉煌气象历史，又是较先让气象部门走入市场运作的少数国家之一，对我们具有重要学习、借鉴意义。因此，我省气象局组成６人代表团，由霍成福局长率团对英、德两国的气象工作进行了认真的考察，收益匪浅，感悟甚多。１概况英国是一个美丽的岛国，坐落在欧洲西部茫茫大西洋中，碧波滚滚的大海将它与欧洲大陆隔开，人们称“英伦三岛”，实际上是由两个较大的岛屿…     

Adjoint Matching Condition for Parameterized Discontinuities—A Derivation Using Lagrangian-form Costfunction

ＡｄｊｏｉｎｔＭａｔｃｈｉｎｇＣｏｎｄｉｔｉｏｎｆｏｒＰａｒａｍｅｔｅｒｉｚｅｄＤｉｓｃｏｎｔｉｎｕｉｔｉｅｓ—ＡＤｅｒｉｖａｔｉｏｎＵｓｉｎｇＬａｇｒａｎｇｉａｎ－ｆｏｒｍＣｏｓｔｆｕｎｃｔｉｏｎＸｕＱｉｎ（许秦）ＣｏｏｐｅｒａｔｉｖｅＩｎｓｔｉｔ...     

STUDY ON MIXED MODEL OF NEURAL NETWORK FOR FARMLAND FLOOD/DROUGHT PREDICTION

The paper concerns a flood/drought prediction model involving the continuation of time seriesof a predictand and the physical factors influencing the change of predictand.Attempt is made toconstruct the model by the neural network scheme for the nonlinear mapping relation based onmulti-input and single output.The model is found of steadily higher predictive accuracy by testingthe output from one and multiple stepwise predictions against observations and comparing theresults to those from a traditional statistical model.     

一次龙卷过程的多普勒天气雷达和闪电定位资料分析

利用WSR-98D多普勒天气雷达和闪电定位资料分析了2003年7月8日发生在安徽省无为县境内的一次龙卷过程。此次龙卷产生于低空急流左侧，动力、热力条件均为较有利的大尺度环境，多普勒雷达回波分析发现，龙卷起源于中高层向低层发展的中-γ尺度气旋中。闪电定位资料分析表明，龙卷发生前10min闪电活动开始频繁。龙卷出现后负地闪明显加大，且龙卷闪电存在于雷暴的发展后期、成熟和消亡阶段。此次龙卷的一些基本特征与通常结论有所不同，(1)雷达反射率因子小于通常结论；(2)龙卷风暴发展高度不是很高，回波顶高仅6～9km，类似于普通雷暴；(3)闪电活动中以负地闪为主，正地闪较少，并未出现正地闪一度占主导地位的现象。     

Can Eddy Forcing be Responsible for the Spatial Structure of the Northern Hemisphere Annular Mode?

In order to study the origin of the spatial structure of the Northern Hemisphere Annular Mode (NAM),a linear stochastic model is constructed empirically from the output of a GCM run.Optimal stochastic forcing in terms of the maximum variance contribution,which may be potentially related to the maintenance of the NAM,is investigated.Theoretical analysis on the dominant non-modal response to the stochastic forcing shows that this dominance is jointly decided by the properties of forcing and the non-modal grow...