Sounding-derived indices for neural network based short-term thunderstorm and rainfall forecasts   总被引：1，自引：0，他引：1  

Agostino Manzato   《Atmospheric Research》2007,83(2-4):349-365

A neural network-based scheme to do a multivariate analysis for forecasting the occurrence and intensity of a meteo event is presented. Many sounding-derived indices are combined together to build a short-term forecast of thunderstorm and rainfall events, in the plain of the Friuli Venezia Giulia region (hereafter FVG, NE Italy).For thunderstorm forecasting, sounding, lightning strikes and mesonet station data (rain and wind) from April to November of the years 1995–2002 have been used to train and validate the artificial neural network (hereafter ANN), while the 2003 and 2004 data have been used as an independent test sample. Two kind of ANNs have been developed: the first is a “classification model” ANN and is built for forecasting the thunderstorm occurrence. If this first ANN predicts convective activity, then a second ANN, built as a “regression model”, is used for forecasting the thunderstorm intensity, as defined in a previous article.The classification performances are evaluated with the ROC diagram and some indices derived from the Table of Contingency (like KSS, FAR, Odds Ratio). The regression performances are evaluated using the Mean Square Error and the linear cross correlation coefficient R.A similar approach is applied to the problem of 6 h rainfall forecast in the Friuli Venezia Giulia plain, but in this second case the data cover the period from 1992 to 2004. Also the forecasts of binary events (defined as the occurrence of 5, 20 or 40 mm of maximum rain), made by classification and regression ANN, were compared. Particular emphasis is given to the sounding-derived indices which are chosen in the first places by the predictor forward selection algorithm.  相似文献   

Relationships between air mass properties and mesoscale rainfall in New Zealand's Southern Alps     

D. S. Wratt  M. J. Revell  M. R. Sinclair  W. R. Gray  R. D. Henderson  A. M. Chater 《Atmospheric Research》2000,52(4)

This paper identifies relationships between air mass properties and mesoscale rainfall when moist air blows over New Zealand's Southern Alps from the Tasman Sea. Around 50% of the variance in six-hourly rain volumes summed across three separate cross-mountain raingauge transects and in six-hourly rain volume spilling across the alpine divide are statistically explained by the following properties of the approaching air mass: relative humidity, wind velocity normal to the mountains, air mass stability and synoptically induced upward motion. These factors also explain about 25% (r≈0.5) of the variance in the downwind distance reached by the spillover rainfall. For the highest 10% of six-hourly rainfalls, spillover distance and magnitude are negatively correlated with the 700 or 500 hPa temperature. Multiple linear regression equations suitable for predicting rainfall intensity and spillover are developed. A progression is described in the magnitude and depth of vertical motion and resulting condensation rates over the mountains as the properties of the incoming air mass evolve through a storm. These changes, together with greater downwind advection of ice particles compared to raindrops, explain the observed statistical relationships between the air mass properties and mountain rainfall.  相似文献   

前期夏季西太平洋暖池热含量对江南春雨的影响及其可能机理   总被引：4，自引：1，他引：3  

尚可  詹丰兴  何金海  祁莉 《海洋学报》2014,36(1):86-97

利用GODAS海洋温度资料、中国753站逐日降水资料以及NCEP/NCAR逐日再分析资料讨论了前期夏季西太平洋暖池热含量异常对江南春雨的影响,并通过高低层环流异常解释了其可能过程和机制。研究结果表明:(1)前期夏季暖池区热含量影响春雨的敏感海区位于9°~16°N,150°~166°E,与春雨强度呈显著反相关,前期夏季关键区热含量的显著偏低是春雨异常偏多的强信号。(2)多雨年和少雨年大气环流差值场与夏季暖池热含量(取反号)回归的次年春季大气环流形态基本一致。低层菲律宾海异常反气旋西北侧的暖湿西南气流输送及江南地区高层辐散抽吸运动是造成春雨偏多的直接原因。(3)关键区热含量在前期夏季的异常偏低使低层异常反气旋在其西北侧触发生成,并在菲律宾海附近持续存在(前夏至当年春季),春季引导强盛的西南气流向江南输送水汽;同时,热含量异常偏低在我国大陆东部激发出高层异常气旋并持续维持(前秋至当年春季),导致春季西风急流轴异常南压,高层形成异常辐散中心,形成强烈的抽吸作用,导致江南春雨显著偏多。前夏热含量显著偏高引起江南春雨偏少的过程则与之相反。  相似文献   

加密自动气象站雨量计资料的质量控制 及其相关关系的研究   总被引：3，自引：1，他引：2  

刘雨佳  陈洪滨  金德镇  齐彦斌  崔莲 《大气科学》2014,38(1):159-170

在长春—四平地区100 km×100 km的范围内,分布有平均间隔10 km左右的147个自动气象站。结合该区域雷达回波强度资料,对2007～2011年4～10月的气象站雨量计小时降水数据进行质量控制。多步骤质量控制结果显示,有141个自动站雨量计的数据通过了检查,删除了6个错误站点的数据,对有疑问时段的数据作了标记。 利用质量控制后的5年夏季半年自动站雨量计小时降水数据,进行相关关系统计分析表明：距离在10 km以内的雨量计测量,平均相关系数均能达到0.6以上;雨量计距离小于5 km,平均相关系数在0.7以上;而站点距离超过20 km,相关系数普遍降到0.4以下;随着统计时间的增长（从分钟到月降水量）,每个雨量计的测量值具有更高的空间代表性。  相似文献   

近50年云南省雨日及降水量的气候变化   总被引：3，自引：0，他引：3       下载免费PDF全文

符传博  吴涧  丹利 《高原气象》2011,30(4):1027-1033

利用1959-2009年云南省30个测站逐日降水资料,通过计算趋势系数、相关系数等现代统计诊断方法,分析了近50年来云南省年、季、月雨日和降水的时空变化特征。结果表明,云南省多年平均雨日空间分布和降水量空间分布基本一致。降水量最大值出现在滇西南地区,滇中到滇东南地区相对较少;年雨日最大值也出现在滇西南地区,滇中地区最少...  相似文献   

四川东部和重庆西部一次ＭＣＣ致洪暴雨过程综合分析     

井喜  艾丽华  廖瑞德 《陕西气象》2011,(1):1-7

吕梁山区出现局地大暴雨为小概率事件,在县局的订正预报中有很大的难度。2010年8月11日位于吕梁市东北端的岚县出现了106．2mm的大暴雨,而吕梁的其它县、市只出现中雨以下量级降水。本文分析了造成本次强降雨的高低空环流形势、主要影响系统、水汽条件、云图与雷达回波资料以及本县特殊的地形特征等结果表明：本次局地大暴雨天气是由高空短波槽、中层切变线、副热带高压边缘西南暖湿气流共同作用产生的;对流层低层强盛的偏南气流为大暴雨提供了源源不断的水汽;地面弱低压加强了辐合上升运动,特殊地形的抬升与阻挡作用,使强回波雨团长时间在迎风坡下的平坦地段停留,从而造成局地性的强降水。  相似文献   

Merging Massive Star Clusters as Building Blocks of Dwarf Galaxies?     

M. Fellhauer  P. Kroupa 《Astrophysics and Space Science》2002,281(1-2):355-358

Recent spectroscopic observations of galaxies in the Fornax-Cluster reveal nearly unresolved ‘star-like’ objects with red-shifts appropriate to the Fornax-Cluster. These objects have intrinsic sizes of ≈ 100 pc and absolute B-band magnitudes in the range - 14 < M_B < -11.5 mag and lower limits for the central surface brightness μ_B ≥ 23 mag/arcsec² (Phillipps et al., 2001, Hilker et al., 1999), and so appear to constitute a new population of ultra-compact dwarf galaxies (UCDs). Such compact dwarfs were predicted to form from the amalgamation of stellar super-clusters (= clusters of star clusters; not to confuse with super stellar clusters (SSC)) by P. Kroupa (1998), which are rich aggregates of young massive star clusters (YMCs) that can form in collisions between gas-rich galaxies. Here we present the evolution of super-clusters in a tidal field. The YMCs merge on a few super-cluster crossing times. Super-clusters that are initially as concentrated and massive as Knot S in the interacting Antennae galaxies (Whitmore et al., 1999) evolve to merger objects that are long-lived and show properties comparable to the newly discovered UCDs. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

A case study in catchment hydrochemistry: Conflicting interpretations from hydrological and chemical observations     

Alan Jenkins  Robert C. Ferrier  Ron Harriman  Yinka O. Ogunkoya 《水文研究》1994,8(4):335-349

Soil water, stream water, groundwater and rain water were sampled through a storm event in a moorland catchment. Samples were analysed for major ions and deuterium. Chloride and deuterium are used as tracers to enable separation of the stream runoff hydrograph into three components: rain, soil and groundwater. The results indicate that rain water arrives in the stream quickly during the event and contributes a significant volume to the runoff peak. The chemical signal in the rain water is, however, significantly damped, apparently due to mixing with soil water held in the catchment before the event. This is further modified before reaching the stream, apparently through mixing with a deeper groundwater component. Interpretation of tracer, chemistry and hydrological data to present an integrated picture of catchment hydrochemical response is difficult due to problems in the chemical and conceptual definition of the flow components.  相似文献   

新疆阿什库勒盆地大黑山火山地质及地球化学特征   总被引：2，自引：1，他引：1  

赵波  许建东  肖旭  孙洪亮  张柳毅  陈正全 《岩石学报》2014,30(12):3531-3538

大黑山火山是新疆阿什库勒火山群最大的火山,通过野外地质调查和遥感解译,火山锥体由渣锥、溅落锥和寄生火山锥组成。大黑山岩石类型分别为玄武粗安岩、粗面安山岩和粗面岩,钾玄岩系列。岩浆分离结晶特征明显,斜长石晶体析出导致残余熔体中δEu形成明显负异常。大黑山锥体南侧发育一套长约1.3km的碎屑熔岩。该套岩石显微薄片上表现为发育玻晶交织结构和溶蚀结构等熔岩结构特征,少许凝灰结构。碎屑主要为5~6cm的角砾,含少量的火山弹。角砾可能来自于大黑山火山较强的爆发,生成岩屑以及少量凝灰质碎屑。后期熔岩喷泉式喷发形成熔岩流,在流动过程中裹带大量的岩屑以及少量凝灰质碎屑。该套碎屑熔岩的发现,加深了对整个地区火山活动类型的了解。  相似文献   

冬奥会张家口赛区一次降水相态特征分析     

马梁臣  马洪波  张曦丹  陈子健  李江波 《气象与环境学报》2022,38(1):1-7

利用冬奥会气象观测站网资料、ERA5的0.25°×0.25°高分辨率再分析资料、常规探空资料以及激光雷达和风廓线雷达资料,从环流形势、温湿度和微物理特征以及雷达特征等方面对2020年11月17-19日冬奥会张家口赛区一次明显的雨转雪天气过程进行分析。结果表明：低层前期的暖湿西南气流,为降水提供好的水汽和能量条件,后期强的干冷平流为相态转换提供有利条件。赛区出现雨转雪时,700 hPa温度低于-2℃,同时850 hPa温度低于2℃。零度层高度的快速下降是相态转换的重要温度判据,0℃线降到距地面400 m左右赛区降水相态已经转变为纯雪,低层风向的转向对赛场的雨雪相态转换有一定的指示意义。随着高空云冰和雪水含量逐渐增加,其出现最大值后,雨雪相态开始转换。降雪时激光雷达最大探测高度比降雨时有明显的降低,风廓线雷达低层风场的变化和雨雪相态关系密切,风廓线雷达探测的垂直速度变化也能反映雨雪相态的转换。  相似文献