一次飑线天气过程分析

从天气形势、物理量场、垂直风切变、气象台自记记录等方面分析了2005年5月6日02时左右(北京时,下同)发生在深圳市的一次强对流天气的形成机制,发现该过程是一次明显的飑线天气过程,其触发机制为:地面弱冷锋、低空急流、垂直风切变共同作用的结果。     

一次弱环境风切变下的强对流天气

本文对2012年7月15日发生在黑龙江省西北部一次弱环境风切变条件下的强对流天气进行了分析,在综合各种常规观测、卫星及多普勒雷达资料的情况下,详细讨论了此次强对流天气发生发展的环流背景场及物理量的变化,着重分析了垂直风切变较弱时仍能发生强风暴所需的条件.结果表明:在丰富的水汽条件、不稳定的层结和一定的触发机制等条件下,环境风切变较弱时也可产生强对流天气.     

基于多普勒天气雷达的低空多普勒速度的切变识别算法研究

低空风切变是影响航空器起飞和着陆安全的重要因素,利用多普勒天气雷达径向速度数据,从风的空间和时间变化上对低空风切变的识别进行了研究,并利用一次飑线过程和一次低空急流过程的资料对识别算法进行了验证。识别算法的核心是分别计算二维合成风切变、垂直风切变和时间风切变。在计算二维合成风切变时,先利用风切变强度因子自适应地选择拟合“窗口”的大小,再利用最小二乘线性拟合方法,得到水平风切变。结果表明:自适应多尺度最小二乘法得到的合成风切变,在低空风切变识别效果、切变连续性和边缘数据处理等方面都优于我国多普勒天气雷达的PUP合成风切变;垂直风切变反映了雷达径向速度的高低空配置情况;时间风切变可提供径向速度随时间的变化情况。算法还可应用于民航机场低空风切变的识别和预警。      

2014年春季华南地区两次强对流天气过程对比分析

基于常规观测、气象卫星和雷达等资料,利用WRF模式对2014年3月31日和5月17日发生在华南地区的两次强对流天气过程的水汽条件、不稳定层结、抬升触发机制、垂直风切变,以及分别造成不同程度灾害性天气的机制进行了对比分析。结果表明： 1） 两次强对流天气过程,均是在充足的水汽和不稳定层结条件下,由850 hPa切变线与地面锋面共同抬升触发而成。在移动过程中强对流前部和后部低层都存在有组织的上升和下沉运动,配合大气环境中有利的垂直风切变,有利于强对流系统内部不断触发新的对流单体生成,从而维持了两次强对流过程完整的回波形态和较长的生命史。2） 在低层0—3 km高度,两次强对流均存在风随高度顺时针旋转、垂直风切变,但3月31日过程的风随高度顺时针旋转更显著,风速增大更明显,垂直风切变更大。在移动过程中强回波后部均有冷池结构形成,但3月31日过程的冷池强度、分布范围和厚度都明显强于5月17 日过程。这种显著差异,使得前者更有利于出现大风、冰雹等灾害性天气。 归纳出的基于“配料法”的预报思路：在水汽条件充足、K指数大于38°C、CAPE大于1 400 J/kg、SI指数小于-2,有锋面、切变线等抬升触发条件存在的情况下,在华南地区需要考虑对流天气发生的可能;当低层0—3 km高度出现风向强烈顺时针旋转、风速增大、垂直风切变增强,并出现强冷池中心时,还需要考虑有组织的强对流天气生成,这有利于提前做好冰雹、大风预警预报。     

浙东海岛两次强对流天气对比分析

对比分析了2004年发生在舟山的两次相似的强对流天气过程,不同在于一次过程强降水特别突出,一次过程强风特别突出。通过对两次过程反射率因子、径向速度以及一些二次产品的对比分析,找出了一些相同点和不同点。组织结构性好的强回波、速度产品中的大风区、垂直风切变、较高的顶高和大的VIL值等是产生雷雨大风和短时强降水天气的共同特征。回波移速较慢的易产生强降水,回波移速快的易产生强风。强风天气的回波强度、顶高和VIL等产品都有更强的表现。低层水平风的辐合、中气旋、垂直风向切变等可以产生强降水,中高层的中气旋、垂直风切变可以产生下击暴流、冰雹等强对流天气。     

2008年1月末九江雨凇转大雪天气过程成因分析

对2008年1月25—29日九江市一次雨凇转大到暴雪天气过程的大气垂直结构进行了分析。结果表明,在雨凇和降雪区域中层有暖层,低层有冷层,且存在对称不稳定层结。垂直风切变明显,有利于对称不稳定能量积累和上升气流的形成。高、低空急流辐散、辐合相互垂直,引发的较强上升运动是雨雪天气得以维持的重要条件。东西风向切变使冷、暖气流在雨雪区域上空交汇,形成水平气旋性辐合,产生垂直运动,且与垂直风切变相互作用,促动上、下层动量传递,使高、低空急流维持。雨凇转大到暴雪时,暖层气温降低,垂直风切变向上增强,对称不稳定能量增大,风向切变辐合加大,上升气流和水汽输送加大。     

河南一次大范围强风暴天气特征综合分析

利用常规和加密实时探测资料,对河南一次大范围强风暴天气过程进行了综合分析,结果表明:这是一次东北冷涡稳定维持,河南受强西北气流影响下的一次大范围强对流天气.高空冷平流,近地面层有暖中心,大的对流有效位能是强风暴天气发生的不稳定层结条件;地面辐合线后东路弱冷空气扩散是强天气的触发机制.中等到强的垂直风切变有利于对流风暴的...     

低空风切变的分析与预报

低空风切变是飞机起飞和着陆阶段威胁飞行安全的主要危险天气，分为水平风的垂直切变、水平风的水平切变、垂直气流切变三种类型。低空风切变主要是由大气运动的变化所造成，强对流天气、锋面天气、低空急流天气都可能引起低空风切变；另外，特别的地理环境也是不容忽视的因素。     

两次暴雨过程的多普勒天气雷达资料对比分析

本文通过对2003年6月22日和7月14日二次暴雨天气过程的多普勒天气雷达资料的分析，发现中低空的水汽辐合、中低空急流和低层垂直风切变引起的辐合是引起强降水的重要原因。表明多普勒天气雷达已成为暴雨短时预报的一种重要工具。     

一次弱对流天气降雹成灾的雷达回波特征分析

通过对新疆玛河流域一次冰雹天气雷达资料及地面实况资料的分析,研究弱对流云降雹的雷达反射率因子与径向速度场的回波特征,进一步探讨弱对流云降雹与0℃层高度较低及垂直风切变的关系：弱对流天气当日零度层高度值可作为分析弱冰雹云的依据;高低空风速的差异形成的风切变造成的动压力产生垂直加速度,使对流运动得到加强和维持,也是此次降雹的动力机制。分析此次天气,揭示了新疆玛河流域弱对流云降雹天气过程生消的一些重要特征和变化,对雹云的识别和分析具有一定的指导意义。     

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.