2005年7月30-31日新乡市连续两夜暴雨过程分析

对2005年7月30-31日新乡市连续两夜出现的暴雨过程诊断分析结果表明:两夜暴雨均是在有利的大尺度环境条件下,激发中尺度系统发生发展而引起.连续两夜出现的暴雨,均处在强上升气流区域的北部边缘,而不是强上升气流中.在θse陡立密集区有利于湿斜压不稳定能量的聚集和中尺度天气系统的发生发展.对流场进行尺度分离,有利于发现形成暴雨的中尺度系统.     

湘西北一次大暴雨过程中尺度结构特征分析

利用常规观测资料、区域自动气象站资料、多普勒雷达资料、美国GFS及LAPS分析资料,对2012年6月下旬发生在湘西北的大暴雨过程的成因以及β中尺度系统的三维动力热力结构特征进行了分析,结果表明:此次过程属于典型的湖南盛夏低涡切变型暴雨过程,地面降水在时空分布上具有明显的中尺度特征。低空急流加强北推不但有利于水汽和不稳定能量向暴雨区的输送,也是β中尺度低涡发生发展和垂直上升运动加强的主要原因。地面中尺度辐合线的维持和地形的阻挡有利于暖湿气流的抬升,而上升的暖湿空气在中高层凝结释放潜热,对上升运动起到正反馈作用。产生暴雨的β中尺度系统具有明显的动力、热力结构特征。在暴雨发展的最强阶段,β中尺度系统的四周各有一个垂直环流圈,其中南北两侧的下沉补偿气流向暴雨区的分支不但有利于水汽和不稳定能量的输送,也加强了暴雨区低层的辐合;东西两侧下沉补偿气流向暴雨区的分支加强了暴雨区气流的气旋性弯曲,更进一步加强了β中尺度系统的辐合;基于上述研究成果,提炼了此次低涡切变线暴雨的三维物理结构示意图。      

2011年6月湖南两次暴雨过程的中尺度特征对比分析

利用常规观测资料、卫星、雷达资料以及NCEP再分析资料、LAPS局地分析资料,对2011年6月湖南两次暴雨过程的中尺度特征进行对比分析。结果表明：两次过程均属于湖南盛夏低涡冷槽型暴雨过程,但中尺度特征、降水性质和环境条件有差异。“6.09暴雨”由一个及地的β中尺度低涡产生,过程期间低涡稳定少动,卫星云图上表现为一个发展强烈的中尺度对流云团,雷达回波前期为窄型带状积云降水回波,后期逐渐转变为积层混合云降水回波;而“6.13暴雨”影响系统为中尺度切变线,切变线维持时间长,移动缓慢,卫星云图上是一条长时间维持的对流云带,雷达回波为积层混合云降水回波。水汽输送通道的建立和中低层水汽的大量集中为中尺度对流系统的发展提供了有利的环境条件,暴雨发生在锋前高温高湿的不稳定层结和强上升运动区域中,锋区的动力强迫上升运动加强了低层能量和水汽的往上输送。两次过程中尺度对流系统均具有深厚的垂直环流结构,“6.09暴雨”湘东北特大暴雨区是一支近乎垂直的深厚上升气流,南北两侧有明显的补偿下沉气流,而“6.13暴雨”湘中暴雨区垂直上升运动是倾斜向上的,只有南侧存在补偿下沉气流。     

河南特强暴雨β中尺度流场发展机理的数值模拟研究

采用宇如聪等研制开发的η坐标有限区域中尺度暴雨数值预报模式AREM,对2004年7月16—17日发生在河南的一次特大暴雨过程进行了数值模拟。模拟结果表明:凝结潜热促使对流层中层大气在β中尺度水平范围的气柱内得到加热,中高层大气的等压面抬高并形成β中尺度高压,中低层大气的等压面降低并形成β中尺度低压,上下层的共同作用促进了垂直运动的迅速发展。当上升运动强烈发展时,在其四周有明显的补偿下沉气流出现:在强上升运动南侧,对流层高层辐散气流向南回流导致对流层高层出现中尺度垂直环流圈,它的下沉支融入上升运动区南侧的补偿下沉气流中,并将高空的水平动量带到对流层低层形成一支新的β中尺度急流;在强上升运动北侧,对流层低层发展出了一支中尺度垂直环流圈,其下沉支向南的辐散气流与低层西南暖湿气流汇合,形成β中尺度辐合线,加强了暴雨区上空低层的辐合;在强上升运动东侧,对流层低层也有一支中尺度垂直环流发展,其下沉支中向西的辐散气流使该区域原来较为一致的西南气流出现向东的偏转,从而在西南气流中形成气旋性弯曲,更进一步加强了β中尺度辐合线上的辐合。对流层低层非地转涡度的强烈发展是β中尺度气旋形成的重要原因。最后给出了强暴雨β中尺度流场发展机理的三维空间示意图。     

2011年7月31日黑龙江省暴雨天气诊断分析

应用常规观测资料、NCEP再分析资料和卫星云图产品,对2011年7月31日黑龙江省西部暴雨天气成因进行诊断分析。讨论了产生暴雨的天气系统特征,大气不稳定条件及产生暴雨的水汽条件和动力触发机制。结果表明：暴雨是由低涡、低涡槽前暖湿气流与冷空气的共同影响产生的。低层强盛的偏南气流建立起水汽通道,将水汽源源不断地向暴雨区输送。低层增温增湿使得大气层结不稳定。低层较强的西北气流与强盛的东南暖湿气流汇合,产生强切变,辐合上升运动增强,为暴雨的产生提供了动力条件,有利于不稳定能量释放。高层辐散与低层辐合相配合,有利于上升运动发展和维持。地面中尺度低压和中尺度辐合线为中尺度云团的发展和维持提供了条件;中尺度云团在暴雨区旋转停留近21 h,这是暴雨发生的主要原因。     

长江中游复杂地形和盛夏局地大暴雨

本文利用武汉WSR-81S数字化天气雷达资料和其它中尺度气象资料分析了1987年8月18日相继发生在长江中游复杂地形区域的两场短历时局地特大暴雨的中尺度演变过程。在没有明显的次天气尺度上升运动直接启动和组织的情况下,两场局地大暴雨暴发的时间和地点都取决于边界层中尺度风场强辐合的出现。复杂地形对边界层气流的热力和机械的综合作用,在一定的大尺度气流背景下,形成有规律的中尺度近地面风场系统。它表现得相对定常并有一定的日变化,当来自临近地区的中尺度对流系统移近时,对流降水中产生的中尺度气流(例如飑锋)参加到由地形影响形成的中尺度边界层流场系统中,便在某些特定地点构成强的辐合。在这类辐合区中心的偏北一侧发展起强大而移动缓慢的复合单体或超级单体,带来局地大暴雨。山谷风环流、平原-山脉环流对盛夏局地暴雨的影响应受到重视。     

2008年8月1~2日滁州特大暴雨双多普勒雷达三维风场反演试验的初步结果

受“凤凰”低压和冷空气共同影响, 2008年8月1~2日安徽省东部和江苏西部部分地区出现大雨, 局部地区暴雨到特大暴雨。滁州和全椒24 h雨量分别为429 mm和414 mm, 此次特大暴雨具有局地性和降水强度大的特点。使用南京和马鞍山双多普勒雷达时间同步观测资料, 对此次暴雨的三维风场进行反演, 在此基础上, 研究了暴雨的三维风场结构。由雷达回波分析可知, 此次暴雨是由β中尺度对流系统造成的, 在β中尺度对流系统内部还有γ中尺度对流单体, 对流单体发展非常旺盛。中低层切变线自西向东移入降水区后, 在该地区停留较长时间, 加之有充足的水汽供应, 造成了局地特大暴雨。在垂直剖面内, 对流系统发展旺盛, 强降水区上空回波较强且对应着较强的上升气流区, 而在强回波中心区的两侧均有下沉气流。当切变线减弱并移出降水区后, 强降水停止。     

一次副高控制下的江西暴雨过程模拟分析

利用WRF数值模式输出的高分辨率模式资料,对2010年7月14—15日江西出现的一次副高控制下的暴雨过程进行了分析。结果表明,此次暴雨过程同样也存在充沛的水汽输送,比湿、水汽通量散度基本都达到江西暴雨的阈值;暴雨区以北能量锋区密集,梯度达到12 K/纬距,大暴雨出现在强能量锋区南缘的高能量舌中;干冷气流侵入地面暖槽,地面扰动有利于强不稳定能量的释放,激发中尺度对流系统发展;强降水发生在切变线附近的西南气流中,并且强降水发生时中低层为一致的上升运动;低层辐合、高层辐散的抽吸作用对上升运动的维持十分有利;300 hPa层以下有正涡度柱存在,在其两侧有下沉气流,并有次级环流存在。     

0505号“海棠”台风暴雨数值模拟试验和分析

利用中尺度数值模式WRFv2.2较好的模拟结果, 并结合NCEP再分析资料、 地面自动站降水资料以及实况雷达回波资料对台风 “海棠” 造成的浙闽地区特大暴雨进行分析。研究发现, 这次暴雨属于台风中心北侧附近的螺旋云带降水, 主要是由边界层强中尺度辐合带直接影响造成的, 降水伴随着辐合带发展; 边界层顶的强东风急流和对流层低层强偏南气流在浙闽地区的交汇是强辐合带的成因; 台风向西北方向移动相伴东风急流和强辐合带的北移, 这是本次暴雨出现稳步北抬的原因。台风的三支不同气流在浙江南部和福建北部地区交汇上升, 起到了水汽通道和能量输送以及建立不稳定区的作用, 提供了暴雨的增幅与维持, 而气流的汇合主要发生在边界层内, 这也是中尺度辐合带高度受限于边界层的原因。浙闽地区复杂的中尺度地形对本场暴雨的发生有重要作用, 为暴雨的增幅做出了重要贡献, 但是, 对边界层不同气流造成的中尺度辐合带而言, 地形的作用较小, 仅可阻挡降水向西延伸。     

一次热带低压引发上海特大暴雨过程的中尺度系统分析

作者利用每日4个时次的1.×1. NCEP资料、逐时的GMs 5卫星红外云图资料、雷达组合反射率及雷达回波顶高图像资料和上海雨量自动站观测资料,对2001年8月5至6日上海特大暴雨过程进行了分析,认为:(1)停滞在上海地区的热带低压为此次特大暴雨的发生提供了有利的背景,而低压内部不断更替出现的中尺度对流云团是暴雨的直接制造者;(2)5日夜至6日晨,热带低压内至少有四个中尺度雨团发生发展,雨团的水平长度小于100 km,宽度约50km,生命史1～3 h不等,属于典型的β中尺度系统;(3)来自西太平洋和南海的暖湿气流向上海地区输送了充足的水汽;(4)热带低压内对流层低层的辐合、高层的辐散有利于强上升运动的维持,强上升气流携带充足的水汽、能量有利于对流云团的发生发展,产生降雨.     

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.     

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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