广西一次大范围西南涡暴雨过程多尺度特征分析

利用常规观测资料、地面自动站资料、FY2E卫星云图和雷达资料对2014年8月广西一次大范围西南涡暴雨过程大尺度环境特征、中小尺度系统特征等多尺度多角度进行分析,结果表明:西南涡和低涡切变是这次暴雨过程的直接影响系统,雨带与850hPa低涡切变活动密切相关,主要降雨区在西南涡、切变线附近和移动方向的前侧;850hPa水汽通量散度辐合中心、等值线密集区对强降水落区分布有较好的指示意义。降雨过程在一定程度上可以体现为中尺度系统的生消、移动,较强的对流回波和列车效应是造成柳江出现强降雨的重要因素。     

引发暴雨的西南低涡特征分析

利用NCEP1°×1°再分析资料、逐时卫星云图资料和自动站资料,分析了与4次暴雨过程密切相关的中尺度系统西南低涡。结果表明,引发暴雨的西南低涡相对于环境场是湿涡,南边界是主要水汽输送方向。在西南低涡形成阶段,整层均为正涡度,一般维持深厚的上升气流,具有较为深厚的暖心结构。在其发展旺盛阶段,正涡度呈上升趋势,对流层中低层...     

“2002.6.30”滇中低涡暴雨的中尺度分析

利用MICAPS常规资料和GMS卫星云图，3830—C多普勒雷达观测资料，对2002年6月30日发生于滇中地区的暴雨天气过程进行诊断和分析，发现暴雨过程由中低层低涡切变造成，暴雨区与垂直速度及涡度所表现的强烈上升区对应，并伴有高能高湿条件；同时卫星云图上有中尺度低涡云团发展。多普勒雷达回波资料分析表明，暴雨过程中出现了明显的中尺度系统，如中尺度辐合线、中尺度气旋、逆风区等，具有典型的对流型特征。     

怀化三次西南涡暴雨天气过程对比分析

利用常规观测资料、地面区域气象自动站加密资料、卫星以及NCEP再分析资料,对2010年6月、2012年6月、2015年6月3次发生在湖南怀化的暴雨天气过程进行对比分析。结果表明:(1)3次过程均是典型的低涡冷槽型暴雨过程,降雨分布在低涡东南侧及其向东伸展出的切变线附近,对于低涡沿切变线东移的暴雨过程,降雨分布在低涡移动的路径上。(2)中低层中尺度低涡或辐合中心是直接造成暴雨的系统,其发展演变和移动直接影响降雨的落区和持续时间,在卫星云图上反应为中尺度云团的生消。(3)孟湾、南海是怀化暴雨的水汽源地,暴雨发生在高温高湿的不稳定层结和强水汽辐合区域,强降雨是整层水汽通量和水汽辐合共同作用的结果,当两者同步增强并达到极值时,降雨也同步增强,当两者不同步时,不能使用单一要素判断降雨,而要综合考虑。(4)3次暴雨过程都是发生在低层正涡度、负散度和高层负涡度、正散度的高低空耦合结构下。     

一次暴雨过程的中尺度特征分析

利用常规观测资料、自动区域站雨量、卫星云图、雷达资料,对2011年8月15～18日发生在陇南市的一次暴雨过程进行分析。结果表明:前期的高温为暴雨产生积累了大量的能量,西南涡和高原涡2个中尺度低涡的形成和维持配合副高外围西南暖湿气流和南下冷空气共同作用造成此次暴雨。不稳定大气层结在冷空气的触发下,使副高外围较强的西南气流提供输送的水汽在高层辐散低层辐合所产生的抽吸作用下不断上升凝结,致使强降水天气发展和维持。β中尺度对流云团受地形及下垫面等因素影响加强,同时暴雨落区主要在β中尺度对流云团的前沿。强降水与雷达回波剖面图上强回波中心基本一致,强回波的列车效应造成了该区域暴雨的发生。     

2011年湖南一次强暴雨过程中尺度分析

以LAPS局地分析资料为主,综合利用卫星云图、地面自动站资料和NCEP提供的全球分析资料,对2011年6月9—10日湖南一次特大暴雨过程进行了分析,结果表明:降水主要发生在对流云团中亮温TBB-70℃的区域的偏西一侧,在TBB-80℃的区域内降水最强;锋前暖区中的对流云团,在中低层是以条件不稳定机制为主的垂直上升运动,而在中高层,是以条件对称不稳定机制为主的垂直上升运动。中尺度对流系统在不断东移南压的过程中,受高层的辐散性流场的抽吸作用和低层的对流不稳定而发展加强。强气旋性切变和正涡度平流触发中尺度气旋发生、发展,β中尺度涡旋是此次特大暴雨过程的直接影响系统。对整层的高度场和流场进行滤波分析发现,此次暴雨过程中的中尺度气旋活跃,强降水雨团与中尺度低层辐合、高层辐散中心基本重合。利用高(低)层中尺度辐散(合)中心位置确定暴雨中心有一定的预报指导作用。     

中亚低涡引发的两次南疆西部暴雨中尺度特征对比分析

选取南疆西部区域自动气象观测站逐时降水量资料、气象站常规观测资料、FY-2D云图TBB资料、NCEP再分析资料以及ECMWF和T639客观分析场资料,采用统计分析和滤波方法对2012年5月21~23日和2013年5月26~29日2次发生在南疆西部的暴雨过程进行对比分析。结果表明:2次暴雨过程均为中亚低涡影响形成,暴雨中心一致,但降水范围、持续时间和降水强度明显不同,中尺度系统的差异是其可能原因。2次暴雨过程分别由中-β系统和中-α系统影响形成,过程的影响系统尺度小,则雨强大、降水时间短,反之亦然。地形作用下的中低层抬升和辐合是南疆西部降水形成的重要原因。地面辐合线是南疆西部暴雨的主要中尺度影响系统,是暴雨的重要触发机制。冷空气翻越帕米尔高原进入盆地,与盆地暖湿气团交汇,形成强辐合线,不稳定强烈发展,利于出现对流性降水,降水强度大。     

青海东部典型暴雨天气环境场特征和物理量指标

利用常规气象观测资料、卫星云图、自动站和NCEP1°×1°再分析资料,对近年来青海出现的三次典型暴雨个例从天气实况、天气形势、中尺度特征、物理量场、云图演变、自动站气象要素和地形等方面进行分析。结果表明:三次暴雨均发生在青海东北部地区,短时强降水伴雷电,暴雨过程前期晴热少雨,出现异常高温天气;三次暴雨的影响系统是副热带高压、500h Pa低槽、700h Pa低涡切变和地面冷锋等,影响系统的强度和冷空气的势力各有不同;暴雨的局地性强,而500h Pa西南急流、700h Pa低涡、地面辐合线及干线等中尺度系统对暴雨的落区有很好的指示。暴雨过程层结不稳定,暴雨的水汽源地可追朔到孟加拉湾和南海,暴雨区处在中低层水汽辐合带中,为中下层湿、上层(或高层)干的不稳定层结;暴雨区有强烈的上升运动,在400~500 h Pa垂直上升运动达到最强。云图演变上反映是该地区南部对流云与西部短波槽或冷锋云系结合加强类,影响短时强降水的对流云团云顶TBB≤-40℃,强对流发生时,云体亮温增强,同时自动站气象要素的变化为短时临近预报提供参考依据;狭谷效应增强了雨势,是产生局地暴雨的有利地形。     

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。     

2003-08-28致洪暴雨过程的数值模拟分析

利用较高分辨率的非静力中尺度数值模式MM 5和NECP资料,对2003-08-28西北东部致洪暴雨天气过程进行数值模拟,重点研究α、β中尺度系统的发生发展和演变过程,对影响暴雨的物理量诊断分析。结果表明:α中尺度低涡越山后迅速生成发展,在有利背景条件下生成多个β中尺度系统,不同尺度系统共同作用形成本次区域性暴雨。强降水主要出现在低涡系统的发展阶段。暴雨区南侧600 hPa附近存在干冷层,上部大气层结稳定,抑制垂直扩散,有利于水汽和能量沿着低空向雨区集中输送。暴雨区上空水汽和能量以垂直输送为主,同时伴有大量潜能释放。位涡、散度、垂直速度等物理量的空间分布,有利于强对流天气发生。     

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.     

Revisiting the Concentration Observations and Source Apportionment of Atmospheric Ammonia

正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on     

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.     

Information for Authors

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

Information for Authors

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 Scope Advances in Atmospheric Sciences(AAS)is an international journal on the dynamics,physics,and chemistry of the atmosphere and ocean with papers across the full range of the atmospheric sciences,co-published bimonthly by Science Press and Springer.The journal includes Articles,Note and Correspondence,and Letters.Contributions from all over the world are welcome.