河北省中南部一次大雾天气过程分析

对2003年11月河北省中南部大雾天气进行了分析,结果表明与稳定度有关的物理量场的变化不仅是强对流等灾害性天气的预报指标,对大雾天气也有一定的指示意义：雾是在稳定的大气层结下出现的天气现象,根据大气稳定层结的状况及变化,可以判断大雾天气的有无及其生消时间。另外,前期湿度条件的积累也是影响大雾生成的主要原因。     

高光谱大气红外探测仪(AIRS)反演大气不稳定度指数在强对流天气个例中的应用试验

使用探空、NCEP-FNL,数据和高光谱分辨率大气垂直探测仪(AIRS)标准反演数据计算大气不稳定度指数,对2011年6月23日北京强对流天气发生前的本地及上游大气中不稳定能量进行分析研究。分析发现:利用08、14和20时探空数据计算的北京站不稳定度指数显示了在"6·23暴雨"过程发生前后北京上空不稳定能量变化,上游关键区无探空数据;利用NCEP和AIRS数据计算的不稳定度指数显示,强对流天气发生前,在北京的上游关键区大气处于极端不稳定状态(K指数大于40,SI指数小于一5),有利于强对流天气发生。文章的研究结果表明,探空数据时空分辨率较低,不利于监测强对流天气的发生;质量控制后AIRS数据计算的不稳定度指数可以监测对流天气的发生;空间分辨率较低的NCEP数据监测小范围大气不稳定层结能力较低。综上所述,AIRS反演产品具有弥补探空资料时空分辨率不足的优势,利用AIRS L2反演产品计算晴空大气不稳定度指数产品可以监测到"6·23暴雨"天气发生前上游关键区大气层结稳定度状态,为预报员决策提供有效的辅助信息。     

塔中秋冬季大气稳定度频率分布特征

采用温度梯度法、理查逊数法、总体理查逊数法分别分析塔中地区秋、冬季的大气稳定度的差异以及大气稳定度的分布频率特征。结果表明:不同的方法对大气稳定度的计算结果有很大影响,采用Ri法和BRi法能够较好的反映塔中秋冬季大气稳定度的变化;塔中秋、冬季大气层结以稳定层结为主,不稳定层结出现频率次之,中性层结出现的频率最小;秋季、冬季稳定度频率有一定差异,秋季中性层结、稳定层结频率小于冬季,不稳定层结大于冬季。     

塔中秋冬季大气稳定度频率分布

采用温度梯度法、理查逊数法、总体理查逊数法分别分析塔中地区秋、冬季的大气稳定度的差异以及大气稳定度的分布频率特征.结果表明:不同的方法对大气稳定度的计算结果有很大影响,采用Ri法和BRi法能够较好的反映塔中秋冬季大气稳定度的变化;塔中秋、冬季大气层结以稳定层结为主,不稳定层结出现频率次之,中性层结出现的频率最小;秋季、冬季稳定度频率有一定差异,秋季中性层结、稳定层结频率小于冬季,不稳定层结大于冬季.     

强对流降水前大气层结因子的分析

显著性检验方法筛选了14个在强对流降水前大气垂直层结中有明显指示作用的因子，其中K指数、γ与γm在各层中差值的绝对最大值等7个因子的指示作用最明显。这些因子表示了大气层结的对流不稳定、条件不稳定、水汽含量和整层大气的垂直均匀性，可用于短时强对流降水的分析和预报。     

珠三角地区前后汛期强对流过程物理量指数对比分析及阈值选取

珠江三角洲（简称珠三角）地区前汛期强对流是由锋面系统引起,后汛期强对流则多由热力系统引起。利用2004—2006年探空资料计算的物理量,选取与强对流天气相关性好的大气温湿类（整层比湿积分IQ）、层结稳定度类（K指数）、动力类（潜在下冲气流指数MDPI）、热力动力综合类（瑞士第一雷暴指数SWISS00）作为指示因子,通过对各指数的分布特征进行对比分析,分别得到珠三角地区前、后汛期的物理量指数的阈值,为进一步做好珠三角地区未来12小时强对流预报服务。      

上海地区强对流天气短时预报系统

以强对流天气的发生、发展规律为依据,从中尺度数值预报模式输出结果、Ｄｏｐｐｌｅｒ天气雷达、静止气象卫星、ＭＩＣＡＰＳ系统和自动雨量站网等获取大气运动的各种尺度动力条件、水汽条件、大气稳定度和触发机制,各种天气实况等动态变化资料,结合预报员经验,建立了“上海地区强对流天气短时预报系统”（以下简称“预报系统”）,预报系统产品包括强对流天气的形势分析、０～１２ｈ展望预报、０～３ｈ滚动预报及警报。预报系统     

利用贵阳单站对流参数的强降水潜势预报方法研究

该文利用2002-2011年10 a的常规观测资料,筛选出贵阳单站24 h强降水、12 h强降水及6h强降水个例.对大气温湿类、层结稳定度、热力及能量类物理指标与强降水进行相关性统计分析,确立了相关性较好的常用物理指标(IQ、K、mK、SWEAT、Tg).通过分析降水前后其物理指标的变化特征,并利用成功指数建立指标预警阈值.再利用逐步消空法和BP神经网络集成方法对指标进行集成,得到相应的预报模型,从而建立了贵阳强对流天气未来0～6h,0～12h的潜势预报的预警预报指标,对贵阳地区降雨预报具有一定的指示作用.分析表明,利用逐步消空法建立的预报模型要优于BP神经网络集成的模型.     

珠三角地区前汛期强对流潜势预报方法研究

利用2004—2006年前汛期探空资料计算的物理量,选取与强对流天气相关性好的大气温湿类(整层比湿积分IntegralQ)、层结稳定度类(K指数)、动力类(潜在下冲气流指数MDPI)、热力动力综合类(瑞士第一雷暴指数SWISS00)作为预报因子,通过对各指数的空间分布特征和数值进行二值Logistic回归分析,得到各指数的参数估算值,建立强对流诊断预报方程,得到前汛期强对流潜势预报因子P,从而制作珠江三角洲(以下简称珠三角)地区未来12小时出现强对流天气的潜势预报。并用此法回报2003—2006年3—6月前汛期的强对流天气。结果表明,P值大于0.9的准确率可达77.5%,P值小于0.5出现强天气的概率仅为3.8%。由于资料有限,对2007年3—4月发生的7次强对流的经验检验效果不明显,但P值小于0.5时不发生强对流的经验检验效果明显。此法对珠三角地区的短时强降水和雷雨大风等强对流天气的临近监测预警有较好的指示意义。     

春季强对流天气预报方法探讨

春季(3—5月)强对流天气,包括冰雹、冰雹大风、≥20m/s的雷雨大风是金华地区重大灾害性天气之。两年来,我们以天气形势为背景,从分析大气稳定度和单站资料变化规律入手,分月建立了予报指标和予报图,并参考雷达回波资料,开展了预报服务工作,取得了较好的效果。现简要总结如下:     

DIAGNOSES OF THE SEVERE DROUGHT OVER YUNNAN AREA IN THE EARLY SUMMER OF 2005

High temperature and drought occurred in Yunnan province during the late spring and early summer in 2005, which was the most severe event in this region since 1950’s. Based on the observational data and relevant diagnoses, this extreme weather event was studied and discussed. The results show that the occurrence of this event could be due to the following observational facts that happened in 2005. (1) The seasonal adjustment of middle-high-leveled atmospheric circulation was delayed. (2) The cold air activity center was deviated north. (3) The onset of summer monsoon over South China Sea was delayed. (4) The tropical convection activity was much weaker than usual. (5) The subtropical high over the western Pacific was located southwestwards and relatively strong.     

A CLIMATOLOGY OF DEEP CONVECTION OVER SOUTH CHINA AND THE ADJACENT WATERS DURING SUMMER

Due to the higher temporal and spatial resolution and the better integrality of long-term satellite infrared(IR) Brightness Temperature(TBB) data,a climatology of deep convection during summer over South China and the adjacent waters is presented in this paper based on the 1-hourly infrared IR TBB data during June-August of 1996-2007(except 2004).The results show that the geographic distribution of deep convection denoted by TBB ≤-52℃ over South China and the adjacent waters are basically consistent with previous statistical results based on surface thunderstorm observations and low-orbit satellite lightning observations.The monthly,ten-day,five-day and diurnal variations of deep convection in this region are focused on in this paper.There are 5 active deep-convection areas in June-August.The monthly variations of the deep convection are closely associated with the large-scale atmospheric circulations.The deep convection over the land areas of South China is more active in June while that over the South China Sea is more active in July and August.The development of deep convection is prominently intermittent and its period is about 3 to 5 five-day periods.However,the deep convection over the coastal areas in South China remains more active during summer and has no apparent intermittence.The ten-day and five-day variations of deep convection show that there are different variations of deep convection over different areas in South China and the adjacent waters.The tendency of deep convection over the land areas of South China is negatively correlated with that over the South China Sea.The diurnal variations of deep convection show that the sea-land breeze,caused by the thermal differences between land and sea,and the mountain-valley breeze,caused by the thermal differences between mountains and plains or basins,cause deep convection to propagate from sea to land in the afternoon and from land to sea after midnight,and the convection over mountains propagates from mountains to plains after midnight.The different diurnal variations of deep convection over different underlying surfaces show that not only there are general mountainous,marine and multi-peak deep convection,but also there is longer-duration deep convection over coastal areas and other deep convection triggered and maintained by larger-scale weather systems in South China during summer.     

2005年初夏云南严重干旱的诊断分析

利用MM5V3.6模式对2005年4月25日一次典型的西南涡影响下的广西强降水过程进行了数值模拟与诊断分析,结果表明,在500hPa低槽、700hPa西南涡东南移的过程中,在西南涡的南端,由于对流层高层高值干位涡下传引起低层气旋性涡度增加,低涡向南伸出一低槽,使西南涡发展成“北涡南槽”形式,广西强降水出现在西南涡的南伸低槽附近。西南涡的南伸低槽附近垂直剖面上为等θe线陡立密集区,700hPa上MPV1<0,MPV2>0,低层有强烈辐合,高层有强烈辐散,从低层到高层都有上升运动。螺旋度对强降水的落区以及造成强降水的中尺度系统的发展有较好的指示性,它反映了大气的动力场特征,运用螺旋度作强降水预报还要结合水汽和不稳定条件。     

中国龙卷时空分布及其环境物理量特征

利用2004—2012年《中国气象灾害年鉴》和CFSR再分析资料,研究中国龙卷的时空分布以及三个龙卷频发区的环流背景场和环境物理量特征,并比较他们之间的区域差异。结果表明:中国龙卷多发生于春夏季,午后傍晚较多,江苏和广东等平原地区出现龙卷概率最高。龙卷临近时,“江苏及其邻近地区”位于500 hPa槽前,850 hPa上有西南急流,造成了较强的低层垂直风切变;“广东及其邻近地区”在龙卷发生前地面对流有效位能均值达997.3 J/kg,0~1 km螺旋度均值达91 m2/s2,层结不稳定,动力抬升强;“东北地区”受深厚东北冷涡控制,整层水汽含量低,中低层比湿均值小于10 g/kg。通过比较环境物理量平均场的分布特征发现:螺旋度、垂直风切变、能量螺旋度指数和强龙卷参数对分析龙卷发生有很好的指示意义。“东北地区”对流有效位能和比湿均值远低于“江苏及其邻近地区”和“广东及其邻近地区”,但高低空的温度直减率大、中低层的垂直风切变强,该地区也会产生龙卷。      

NUMERICAL STUDY OF INFLUENCE OF THE SSTA IN WESTERN PACIFIC WARM POOL ON RAINFALL IN THE FIRST FLOOD PERIOD IN SOUTH CHINA

1 INTRODUCTION The flood period in South China (SC) lasts long and rains heavily. Its relationship with the SST in the near sea has been studied by Chinese meteorologists early. Liang[1] found that the rainfall of Guangdong in warm water years of South China Sea (SCS) is more than in cold water years. Xie et al[2]. analyzed the relations between the rainfall in Guangdong flood period (from April to September) and SST in northwest Pacific, and built prognostic equations for monthl…     

西太平洋暖池海温对华南前汛期降水影响的数值试验

简要地介绍了全球大气环流模式CCM3,由该模式模拟得到降水、位势高度场和风场,分析它的模拟性能。根据华南前汛期(4～6月)降水与西太平洋暖池敏感海区(西区)海温的负相关关系,设计了两组敏感性试验,讨论西区海温对华南前汛期降水影响的确定性和可能的物理机制。模拟结果表明,当西区为冷水年(暖水年)时,华南降水偏多(少),长江中下游相对偏少(多),相关最好的地区是广东省,与诊断分析结果相符。海温对降水的影响是通过大气环流场来实现的,因此,再用P-σ九层区域气候模式模拟了西区海温异常年大气环流对华南前汛期降水的影响,与CCM3模拟结果基本一致。     

PRELIMINARY ANALYSES OF THE ACTIVITIES OF SOUTH CHINA SEA SUMMER MONSOON IN 1998

The NCEP reanalyzed data, OLR and SST observations are used to study the onset time and the multi-time scales features of the South China Sea (SCS) summer monsoon in 1998 and its interaction with the sea surface temperature and the effect on the precipitation in Guangdong province. It is found that the 1998 SCS summer monsoon set in on May 17 (in the fourth pentad of the month). The year witnesses a weak monsoon with the OLR oscillating at cycles of about 1 month and the Southwest Monsoon of about 1/2 month. The mon-soon over the Bay of Bengal and the cross-equatorial current near 105°are two driving forces for low-frequency variations of the SCS monsoon. The weak activity in the year was resulted from positive anomalies of SST in the equatorial eastern Pacific in early spring and subsequent formation of positive anomalies of SST in the SCS through the Arabian Sea.     

SEASONAL VARIATIONS OF CONVECTIVE ACTIVITIES OVER THE SOUTH CHINA SEA AND ITS NEIGHBORHOOD AND THEIR COMPARATIVE ANALYSES IN THE STRONG AND WEAK CONVECTION YEARS

The seasonal variations of convective activities over the South China Sea(SCS)and itsneighborhood.as well as the similarities and differences of convection in the different key regionsduring the strong and weak convection years are analyzed by using the pentad data of TBB from1980 to 1993.The results show that in winter and summer the seasonal variations of the convectiveactivities are synchronous over the SCS and its neighborhood,the anomalous convection amplitudesare obviously different in different regions.The significant extents of convective activities havesomewhat seasonal differences in the strong and weak convection years.In the strong convectionyears,it is in winter,spring and autumn that the convection anomaly is more evident than that inthe normal years,however,after the summer monsoon onset the convection is sustained.stableand similar to that in the normal years.In the weak convection years.the convection weakensgreatly in each season.but the primary weakening occurs in spring.summer and autumn.Nomatter in the strong or the weak convection years.the convective activities are somewhat ofdifference in the Bay of Bengal.the Indochina Peninsula.the SCS and the Philippines.In addition.the convective activities are also different over the south and the north parts of the SCS.theconvection variation in the strong year is similar to that in the weak year over the north part of theSCS.but over the south part there are great differences.     

SEASONAL VARIATIONS OF CONVECTIVE ACTIVITIES OVER THE SOUTH CHINA SEA AND ITS NEIGHBORHOOD AND THEIR COMPARATIVE ANALYSES IN THE STRONG AND WEAK CONVECTION YEARS*

The seasonal variations of convective activities over the South China Sea(SCS) and its neighborhood.as well as the similarities and differences of convection in the different key regions during the strong and weak convection years are analyzed by using the pentad data of TBB from 1980 to 1993.The results show that in winter and summer the seasonal variations of the convective activities are synchronous over the SCS and its neighborhood,the anomalous convection amplitudes are obviously different in different regions.The significant extents of convective activities have somewhat seasonal differences in the strong and weak convection years.In the strong convection years,it is in winter,spring and autumn that the convection anomaly is more evident than that in the normal years,however,after the summer monsoon onset the convection is sustained.stable and similar to that in the normal years.In the weak convection years.the convection weakens greatly in each season.but the primary weakening occurs in spring.summer and autumn.No matter in the strong or the weak convection years.the convective activities are somewhat of difference in the Bay of Bengal.the Indochina Peninsula.the SCS and the Philippines.In addition.the convective activities are also different over the south and the north parts of the SCS.the convection variation in the strong year is similar to that in the weak year over the north part of the SCS.but over the south part there are great differences.     

100hPa极涡、南亚高压的变化及大气环流分布特征

利用NCEP/NCAR高度场资料进行计算,对冬、夏极涡与南亚高压面积进行Morlet小波变换,并对100 hPa高度场进行EOF分解和长期趋势分析.结果表明:极涡、南亚高压具有相似的演变特征,这种相似特征在前期冬季极涡与南亚高压之间表现更为明显,体现了准5年尺度和准20年尺度的周期变化,在变化的位相上则相反.EOF分析表明,前期冬季高纬度地区与中低纬度地区的环流变化呈相反趋势,且第一模态的时间系数与前期冬季极涡的趋势一致,第一模态在一定程度上反映了前期冬季大气环流分布.夏季第一模态全场为负值,体现了夏季100 hPa整体异常性;第二模态反映了副热带中低纬度大气环流与高纬度大气环流变化相反.从其长期变化趋势来看,冬季高纬度地区的高度场呈负趋势变化,副热带地区呈正趋势变化,夏季除我国华北部分地区为负趋势变化外,均为正趋势变化.极涡、南亚高压的这种年代际变化与100 hPa高度场的长期线性趋势变化有关.