一次强暴雨过程地闪活动特征与中尺度对流系统和强降水的关系

利用2007年8月8日18时至9日02时发生在陕西关中强暴雨期间的地闪、卫星TBB、雷达回波和地面加密降水资料,通过统计和对比分析的方法,分析了地闪活动特征及其与中尺度对流系统（MCS）和强降水的关系。地闪活动特征分析显示,暴雨过程中负地闪占绝对优势,为总地闪的97.7%。负闪频数和总闪频数的逐时演变趋势完全一致且呈现两峰一谷的趋势,正闪频数的变化呈现三峰两谷的趋势,但是正闪频数最大值与总闪、负闪频数峰值时间一致。负闪活跃期正负闪6 min演变均表现为多峰结构,正闪的波峰提前于负闪的波峰12 min。负闪频数变化和MCS、雷达反射率因子演变对比分析表明,负闪发生区是未来对流云团和对流发展加强区,负闪频数密集区位于对流云团前部TBB等值线密集区,负闪频数的急剧增加意味着未来对流系统的猛烈发展;负闪主要出现在回波强度大于40 dBz的区域,正闪则落到强回波中心两侧30～40 dBz的回波区,中尺度对流系统快速发展加强期,负闪密集区位于回波单体的前沿,中尺度系统发展稳定少动期,负闪大部分集中在各对流单体的强回波中心附近。对比分析地闪与暴雨发生发展的关系可见,地闪的发生和急剧增加对暴雨发生和发展加强有很好指示意义,初闪的发生提前于强降水发生,地闪急剧增加与降水强度猛增密切关联,负地闪发生密集区是未来强降水发生区。     

吉林省“7.28”强对流暴雨过程地闪活动特征分析

利用2010年7月27日21时至7月28日20时发生在吉林省中东部强暴雨期间的地闪、风云卫星TBB、多普勒天气雷达和地面加密降水资料,采用统计对比方法,分析地闪活动特征及其与强对流系统和强降水的关系。结果表明:此次暴雨过程中负闪占总闪的95.7%,负闪频数和总闪频数的逐时演变完全一致且呈现两峰两谷趋势,正闪峰值与总闪、负闪峰值出现时间基本同步。正负闪6min演变均表现为多峰波动,负闪的波峰提前于正闪波峰6min左右。地闪发生在长春雷达组合反射率大于35d Bz的区域和TBB等值线密集区;正闪主要出现在云顶黑体亮温大值区前部。逐时地闪峰值与逐时降水峰值变化趋势基本一致,地闪峰值提前于降水峰值4h出现,强对流上升阶段降水强中心未出现在地闪密集区,对流性暴雨下降阶段和中间阶段降水强中心位于地闪密集区。     

070729特大暴雨的地闪特征与降水相关分析

利用闪电定位每分钟的实测资料、加密雨量站每分钟的雨量资料,以及卫星云图资料,对2007年7月29-30日,山西南部产生的特大暴雨的地闪特征进行了综合分析。发现：地闪出现在500hPa的5840gpm与5880gpm之间、TBB≤-43℃的区域内;低空急流左侧3个经距、700hPa暖切变南侧2-3个纬距所围区域与TBB≤-63℃的区域或云团南部TBB水平梯度的大值区相叠合的区域是地闪的高频数区和密集区,该区域与暴雨落区有较好的对应关系;3个中-β尺度对流云团和1个MCC是导致特大暴雨产生的主要对流系统。分析结果表明：两个中尺度云团合并的时刻是闪电频次更高的时刻,两个中尺度云团合并的地点是闪电频次更高更密集、降水更强的区域;利用单站每分钟的地闪累积数以及与加密雨量站每分钟雨量的关系,可以识别中-γ尺度对流系统,遥测小尺度强降水,提前35-40分钟预测雨强峰值的到来;只有在有利的高低层系统配置下,局地地闪频数与雨强随时间的变化才有很好的相关性。     

070729特大暴雨的地闪特征与降水相关分

利用闪电定位每分钟的实测资料、加密雨量站每分钟的雨量资料,以及卫星云图资料,对2007年7月29-30日,山西南部产生的特大暴雨的地闪特征进行了综合分析.发现:地闪出现在500hPa的5840gpm与5880gpm之间、TBB≤-43℃的区域内;低空急流左侧3个经距、700hPa暖切变南侧2～3个纬距所围区域与TBB≤-63℃的区域或云团南部TBB水平梯度的大值区相叠合的区域是地闪的高频数区和密集区,该区域与暴雨落区有较好的对应关系;3个中-β尺度对流云团和1个MCC是导致特大暴雨产生的主要对流系统.分析结果表明:两个中尺度云团合并的时刻是闪电频次更高的时刻,两个中尺度云团合并的地点是闪电频次更高更密集、降水更强的区域;利用单站每分钟的地闪累积数以及与加密雨量站每分钟雨量的关系,可以识别中-γ尺度对流系统,遥测小尺度强降水,提前35～40分钟预测雨强峰值的到来;只有在有利的高低层系统配置下,局地地闪频数与雨强随时间的变化才有很好的相关性.     

060814山西省局地大暴雨的地闪特征分析

利用闪电定位每分钟的实测资料和加密雨量站每分钟的雨量资料,对山西省2006年8月13~14日副热带高压东退南压过程中,产生的局地大暴雨过程的地闪特征进行了分析。结果表明:对流风暴中,负地闪出现在强度达40 dBz且与径向速度图的逆风区或附近正速度的大值区相重叠的区域内,正地闪出现在强度达30 dBz风暴后部的正速度小值区;混合性降水云系中,地闪出现在500 hPa 5880gpm与5840 gpm等高线所包围区域内的辐合带或逆风区,且正地闪靠近5840线一侧,负地闪靠近5880线一侧。局地地闪频数与雨强随时间的变化有很好的相关性,负地闪的出现及其频数的增加意味着影响该地区的对流风暴正在发展并向本地移来,地闪频数峰值的出现表示雨强峰值的迅速到来,正地闪的出现表示该对流风暴对本地区的影响即将结束。利用地闪频数峰值准确地预报强对流风暴产生的局地强降水只有30~45 min的提前量,而对于混合性强降水的预报则可有1~2 h的提前量;逆风区的水平尺度、垂直厚度、逆风区附近的正、负速度差值直接影响风暴降水的范围、强度和持续时间。     

一次云南强对流暴雨的中尺度特征分析

利用NCEP/NCAR再分析资料及常规观测资料与雷达、卫星等非常规观测资料,综合分析了2014年6月6日云南暴雨过程的天气成因及中尺度对流系统特征。结果表明:500hPa前倾槽、700hPa切变线及地面冷锋是此次暴雨过程的天气尺度影响系统;高能高湿的对流不稳定层结、明显的垂直风向切变是强对流天气形成的有利条件;在Q矢量散度辐合区内多个β中尺度对流系统(MCS)发生发展,短时强降水主要出现在MCS移动方前沿对流活跃的云顶亮温(TBB)等值线密集区,雨强变化与TBB等值线梯度变化密切相关;多普勒雷达及地闪资料显示多个γ中尺度对流系统是强对流暴雨产生的直接影响系统,雷暴易发生于回波强度在35~45dBz、回波顶高超过10km的区域,中尺度辐合线、第二类γ中尺度辐合区附近负地闪密集区与短时强降水、雷暴天气有很好的对应关系。     

内蒙古典型暴雨过程的中尺度雨团观测分析

利用FY-2E逐时云顶黑体亮温资料 (TBB)、闪电定位资料、自动气象站资料和逐时降水资料,对2009—2013年6—8月内蒙古7例暴雨天气过程的中尺度雨团特征进行分析。结果表明:内蒙古暴雨的降水强度在1~3 h即可达到暴雨或大暴雨量级,中尺度雨团活动是内蒙古暴雨过程形成原因,而80%雨团活动是中尺度对流系统 (MCS) 造成的。MCS内TBB不超过-52℃冷云区和地闪密度大值中心对雨团强度和发展具有重要的指示作用,冷锋云系中MCS造成的雨团多原地生成和消亡,TBB不超过-52℃冷云区面积小,维持时间为2~8 h,地闪密度增长缓慢而且发生频次低;冷涡云系中雨团跳跃式出现在MCS冷云区或冷空气流入一侧,出现TBB不超过-62℃冷云区,雨团出现频次高,持续出现时间可长达24 h,地闪密度增长迅速且发生频次高。7次暴雨过程中约有60%雨团伴有地闪活动,地闪密度达到最大值时刻预示未来1~3 h最强雨团出现和MCS发展到成熟。地面加密风场中尺度辐合线先于MCS和雨团出现,中尺度辐合线造成的局地辐合可作为MCS发展的启动机制。     

一次东移高原低涡的天气动力学诊断分析

利用地面和高空常规观测资料、NCEP 1°× 1°再分析资料以及时空分辨率较高的 TBB 资料,对造成我国长江流域强降水的一次高原低涡东移过程进行了天气学和动力学诊断分析.主要分析了低涡移动、降水分布及水汽输送、假相当位温和湿位涡等物理量.分析表明此次高原低涡随其东部低槽移出高原,降水主要发生在低涡的东半侧并在低涡移出高原后增强.当低涡与热带气旋合并时,产生强降水,造成了长江流域的汛情.卫星 TBB 图与降水时段和落区对应较好.水汽通量散度场的分布较好地反映了水汽的集散情况,其辐合区与降水区相对应,强辐合中心与强降水中心一致,且强降水中心位于 850 hPa θse 等值线密集区和 500 hPa 的高能区.低涡降水的发生发展与湿位涡的时空演变有很好的对应关系,湿位涡正负区的叠置是低涡暴雨发展的有利形势,强降雨区发生在对流层低层湿位涡正压项的正值区东北和东南侧零线附近,而湿位涡斜压项的负值区对暴雨的落区和移动有一定指示意义.     

内蒙古一次暴雨过程中尺度特征及成因分析

利用常规观测资料、NCEP 1°×1°再分析资料、自动气象站资料、FY-2E逐时云顶亮温TBB资料和闪电定位资料,对2013年7月14-16日内蒙古暴雨过程进行分析。结果表明,此次暴雨过程58%的暴雨站点在2 h、3 h或6 h即达到暴雨量级,强降水造成的中尺度雨团和中尺度雨带是暴雨主要表现特征。强降水是冷锋云系或涡旋云系中不断生消的中尺度对流系统(MCS)直接造成的,在MCS发展和成熟阶段,雨团和地闪密度大值区位于TBB≤-52℃冷云区冷空气流入一侧,但MCS移出区域,也有雨团的出现,是由层状云引发的。地闪密度增加,MCS发展,雨强增强,地闪频次锐减,MCS开始消亡,雨强减弱。阻塞形势稳定、南亚高压东伸和西太平洋副热带高压位置偏北是MCS发生的有利行星尺度背景条件,低空急流日变化是造成强降水集中出现在前半夜至凌晨的主要原因。对流层低层高温高湿、位势不稳定层结和风垂直切变对MCS形成提供了有利环境场。地面中尺度"人"字形切变线形成的扰动机制先于MCS发生,MCS出现在暖式切变线南侧不稳定区,但对流层高层强辐散中心和低层强正涡度中心滞后于强降水峰值出现时刻3~4 h。     

贺兰山东麓两次局地暴雨过程的湿位涡诊断分析

利用自动气象站雨量资料、MICAPS4调阅资料以及NCEP再分析资料,对比分析了2016年8月21日和2018年7月22日宁夏贺兰山东麓两次局地暴雨过程的降水特征、环流形势等,重点对两次过程的湿位涡场进行了诊断分析。结果表明:两次暴雨过程第一阶段均为暖区降水,表现出降水范围小、时间短、强度大,相对第一阶段降水,第二阶段降水范围较大、雨强较小。两次过程强降水均发生在假相当位温(θse)等值线密集区,并沿低空急流轴呈长条状分布,强降水时段与θse最大值出现时间相一致。暴雨区位于位涡(PV)负值中心区附近,暴雨发生发展过程与PV负值中心的移动和变化较为一致,PV负值中心的加强和减弱以及移动方向对局地暴雨的预报有很好的指示意义。对流层500 hPa以上湿位涡正压项(MPV1)正的大值区对应700 hPa以下负的大值区,正负中心区垂直叠加的配置有利于暴雨发生发展。垂直剖面图上600 hPa都存在湿位涡斜压项(MPV2)负极值中心,对流层中低层MPV2负极值中心的强度和维持时间以及变化对局地暴雨的预报有一定的指示作用。     

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.     

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.     

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     

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.     

Editorial

As we will soon celebrate the 90th anniversary of the founding of the Chinese Meteorological Society （CMS）,Acta Meteorologica Sinica （AMS）,which was originally named as Bulletin of the Chinese Meteorological Society,has gone through 89 years of development and excitement since her first issue in July 1925.According to archived documents （CMS Editorial Committee,1925）,AMS was founded to report the research findings of Chinese meteorologists,record their recommendations for improving meteorological services,and share their common meteorological interests in order to promote the growth of AMS such that more members could be inspired to conduct atmospheric research and meteorological knowledge would be better disseminated to and benefit the general public.By upholding and carrying forward this purpose,AMS has published many highly valuable scientific papers.Some could be treated as classical articles,which have produced important influences on both domestic and international meteorological communities and the related fields.