2008年“7.1”鄂东北特大暴雨过程的中尺度分析

利用常规气象资料、新一代雷达和卫星云图资料等,分析了2008年7月1日鄂东北特大暴雨过程中尺度扰动系统的发生发展、暴雨中尺度对流系统（MCS）结构特征以及地形对中尺度系统的影响。结果表明,鄂东北暴雨与中尺度气旋的发生发展关系密切,红安等地特大暴雨就是中尺度气旋波冷切变上激发的多个β中尺度对流系统相继东移产生的;中尺度气旋形成于黄淮锋面气旋波发展阶段,雷达反射率因子形态、结构特征较好地反映了该中尺度气旋波发展过程;对流易在红安西侧加强,同冷空气沿大别山和桐柏山之间南下与天气尺度西南气流交汇形成局地中尺度辐合线有关;红外云图上特大暴雨MCS形态为指状云团,由不同生命史阶段的子云团构成,是产生持续性强降水的云团的显著特征。     

1998年6月8～9日香港特大暴雨中尺度对流系统分析

利用卫星和多普勒雷达的高时空分辨率观测资料,对1998年6月8～9日香港暴雨过程中的中尺度对流系统进行分析,表明:(1)此次暴雨是冷锋前暖区的对流性降水,期间有3次强降水过程,每次维持时间2～5小时,中尺度对流系统是造成强降水的主要系统.(2)雷达回波强度与卫星云图对比发现,强回波区全位于云顶温度≤-32℃的云团内,但具体分布有两种情况:一种强回波区位于通常所说的发展强盛的α中尺度云团的边缘TBB等值线密集区,一种如尺度较小的线状强回波则位于两个β中尺度云团(云顶温度≤-52℃)之间.这利用常规观测资料是无法识别的.(3)分析单多普勒雷达反演的水平风场发现:大尺度的环境风场中,存在β中尺度系统的独立流场;中尺度云团内部的流场辐合与强回波带相对应.     

暴雨多普勒天气雷达回波特征分析及临近预警

对近几年来武汉雷达所观测的典型低涡、梅雨锋暴雨天气过程进行了多普勒雷达观测分析,总结了β尺度暴雨回波系统的基本特征和强降水与诸多因素的关系.分析指出,在短时预报业务中,暴雨回波的识别和预警关键是从整体上要抓住β中尺度暴雨回波系统发生发展的特征,而不是孤立地研究一个对流单体的演变.     

宝鸡2006年7月8—9日连续突发性暴雨的中尺度系统特征分析

利用西安多普勒雷达、FY-2C卫星、自动站加密雨量等资料,对宝鸡2006年7月8日、9日连续突发性暴雨的中尺度系统观测特征分析,结果表明:地面冷锋触发的中-γ尺度对流系统造成这2次暴雨;中-γ尺度对流系统生命史为1h左右,发展迅速,强降水产生于中-γ尺度系统成熟期(前30min);多普勒雷达图上,组合反射率大于45dBz的强回波对应强降水。2次突发性暴雨平均雨强1mm/min,最大4.2mm/min。借助多普勒雷达,可及时捕捉中-γ尺度对流系统。     

2009年7月7日南京短时暴雨的中尺度特征分析

利用FY-2C卫星红外辐射亮度温度(T_BB)资料、多普勒天气雷达资料、加密自动站资料、NECP再分析资料、常规观测资料对2009年7月7日发生在南京地区的一次短时大暴雨过程的中尺度特征进行分析,结果表明:在有利的天气尺度背景形势下,多个中尺度对流系统在南京地区合并,合并后的中尺度对流系统强度强,移速慢,造成了南京地区的强降水。这次短时暴雨的中尺度特征在云图T_BB资料上表现为对流云团合并后强度和范围显著增强,移速缓慢,T_BB梯度大值区在南京地区停留;在地面风场上体现为南移的中尺度辐合线与南京地区局地生成的中尺度辐合中心合并,使得地面风场辐合显著增强;在雷达回波上表现为,南京地区上空不断有对流单体并入形成大面积高效率降水回波,镶嵌其中的γ尺度对流单体沿着相同方向依次通过南京地区。分析中还发现,低空急流、低空切变线是这次短时暴雨天气过程的重要影响系统,利用多普勒雷达资料可以识别和分析它们的发展、变化特征,为短时暴雨的临近预报提供依据。     

一次典型梅雨锋暴雨过程的多尺度结构特征

利用多种类型资料,对2009年6月29—30日引发鄂皖境内梅雨锋特大暴雨过程的天气形势和中尺度对流系统（MCSs）进行了初步分析,揭示了梅雨锋暴雨系统的多尺度结构特征,并用中尺度模式WRF对梅雨锋暴雨系统进行了9km三重双向嵌套大区域精细模拟,再采用Morlet小波变换对模式输出进行空间带通滤波,分离出α、β和γ中尺度系统,对不同中尺度系统的热力动力三维空间结构特征进行了研究。结果表明：梅雨锋特大暴雨由梅雨锋上多个不同尺度的MCSs活动造成,这些不同尺度的MCSs在卫星云图和雷达回波上呈现出不同的特点。在α、β和γ中尺度上,梅雨锋暴雨中尺度系统在水平和垂直方向上的动力、热力结构特征存在着明显的差异,α、β中尺度系统具有明显的垂直环流,而γ中尺度系统则具有惯性重力波特征,往往嵌套在α、β中尺度系统内发生发展。最后,提出了典型梅雨锋暴雨系统的物理概念模型。     

我国西南地区一次暴雨过程特征及成因

利用卫星云图、多普勒天气雷达资料和高空风等各种天气学资料,对2009年6月8—9日广西、贵州、以及和湖南交界地带的一次暴雨过程进行了综合分析。结果表明,暴雨是由中尺度对流复合体东移、β中尺度强对流云团发展、以及二者合并造成的;地面α中尺度低压带配合α中尺度纬向切变线的生成,为中尺度对流复合体（mesoscale convective complex,MCC）的东移发展、β中尺度强对流云团的发展、以及二者的合并创造了有利条件;地面能量比低值舌的活动是MCC和β中尺度强对流云团生成和发展的触发机制之一;在多普勒雷达径向速度图上,MCC的生成和发展,伴随西南低空急流的建立和维持,大范围的逆风区的生成;MCC的消亡,伴随西南低空急流的减弱和消失,对应西北气流建立和东扩。MCC发展期和β中尺度强对流云团发展期、MCC消散期和β中尺度强对流云团消散期的涡度收支以及视热源和视水汽汇有很大的不同。     

东北地区一次短时大暴雨β中尺度对流系统分析

为了探寻东北短历时暴雨的预报线索,利用自动站、卫星和常规气象观测资料相结合的方法,研究2006年8月10日最大1 h雨量达到90.8 mm(泰来,其中,后半小时降水82 mm)的东北中西部百年一遇短历时特大暴雨中尺度对流系统(MCS)发展过程,及其发生的天气尺度背景和中尺度环境与触发机制.通过红外卫星云图和高分辨率的可见光云图,分析MCS如何从一个γ中尺度发展为α中尺度对流复合体(MCC)的过程.分析表明,与6个市(县)半小时雨量超过33 mm相关联的MβCS分别发生在2个阶段,第1阶段在MCC形成之前,MβCS主要向东移动(最后合并成MCC),第2阶段,在MCC成熟阶段.MpCS出现在MCC的西南边缘,而且最强短历时暴雨就发生在这里.从分辨率更高的可见光云图上可以发现,有北、西两条积云线,它们交汇的地方MβCS强烈发展并产生暴雨.分析MCS加强和产生暴雨的原因表明:(1)暴雨发生前夕暴雨区域具有高温、高湿和对流性不稳定层结,并存在明显的对流有效位能增加、抬升凝结高度及自由对流高度降低的现象,有利于暴雨发生;(2)β中尺度云团之间的合并,使MCS迅速发展,产生暴雨;(3)北、西两条积云线分别与地面风场中的两条辐合线相对应,在它们交汇处的较强辐合导致β中尺度云团强烈发展产生暴雨.分析MCS在MCC西南方向传播的原因表明,两条辐合线的移动方向和速度决定了暴雨MCS的传播方向.另外,偏北气流的出现和新老云团的新陈代谢过程是触发暴雨的关键因素.上述分析结果也为短历时暴雨的预报提供了有用的线索.     

季风槽环境中暴雨中尺度对流系统的分析与数值预报试验

应用地面降水观测资料、卫星云图、雷达回波以及NCEP再分析资料,对华南沿海受季风槽影响下发生的一次持续性暴雨的中尺度对流系统（MCS）进行分析,并探讨采用数值模式对中尺度对流系统降水进行预报的可能性。分析表明,暴雨由多个相继发展的中尺度对流系统造成。在相似环境中,不同中尺度对流系统发展形态和水平尺度有较大差异,最大可组织发展成α中尺度对流复合体（MCC）,但一般为β中尺度线状或带状对流系统。对其中发展形态分别表现为椭圆形中尺度对流复合体（MCS-2）和带状β中尺度对流系统（MCS-4）的对比分析发现,对流的起始发展均发生在夜间,与季风槽中低空急流的南风脉动有良好对应关系。基于临近探空资料的诊断发现,被认为对中尺度对流系统组织发展有指示作用的关键物理量如对流有效位能（CAPE）和风垂直切变难以区分不同中尺度对流系统的发展形态和趋势,探空资料的代表性将影响诸如“配料法”等暴雨客观预报方法的建立和应用。利用华南区域中心GRAPES（GRAPES_GZ）数值模式对两个中尺度对流系统进行的模拟预报结果表明,采用数值模式对中尺度对流系统降水进行显式预报已成为可能。比较而言,3 km水平分辨率模式可以更好地预报出暴雨的发生,但结果对是否调用对流参数化（CP）方案敏感。尽管不依靠对流参数化方案模式能够较好地预报出中尺度对流系统初始降水的发生,但会过度预报发展成熟后的降水。模式中如何描述中尺度对流系统对流的组织发展机制、如何处理对流参数化方案的“灰色区分辨率”问题需要仔细考虑。      

梅雨锋暴雨中尺度对流系统研究若干进展

梅雨锋暴雨中尺度对流系统是暴雨的直接影响系统,对其结构特征、活动规律及其发生发展的物理机制的深入研究,对提高梅雨锋暴雨的预报能力有重大意义。近年来对梅雨锋暴雨中尺度对流系统的研究取得了很大进展,文章对梅雨锋暴雨中尺度对流系统研究的若干进展作了简要综述,包括梅雨锋暴雨云系多尺度结构、梅雨锋暴雨的β和γ中尺度系统发生发展的环境条件和结构、云微物理分布和转化特征及其对热力动力过程反馈等方面,并对有关问题进行讨论。     

LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN

Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d.     

AN ATTRIBUTION ANALYSIS OF CHANGES IN POTENTIAL EVAPOTRANSPIRATION IN THE BEIJING–TIANJIN–HEBEI REGION UNDER CLIMATE CHANGE

Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region.     

ANALYSIS OF “BIMODAL PATTERN” STORM ACTIVITY CHARACTERISTICS OF THE BAY OF BENGAL

Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms.     

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959–2014

The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics.     

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正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome.SUBMISSIONAll submitted     

A Brief Introduction to Marine Meteorological Science Experiment Base at Bohe Town,Maoming City,Guangdong Province

<正>With the support of specialized funds for national science institutions,the Guangzhou Institute of Tropical and Marine Meteorology,China Meteorological Administration set up in October 2008 an experiment base for marine meteorology and a number of observation systems for the coastal boundary layer,air-sea flux,marine environmental elements,and basic meteorological elements at Bohe town,Maoming city,Guangdong province,in the northern part of the South China Sea.     

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AIMS AND SCOPE
Atmospheric and Oceanic Science Letters （AOSL） publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome.     

Information for Authors

AIMS AND SCOPE Atmospheric and Oceanic Science Letters （AOSL） pub- lishes short research letters on all disciplines of the atmos- phere sciences and physical oceanography. Contributions from all over the world are welcome.     

Information for Authors

正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences