我国中东部不同级别短时强降水天气的环境物理量分布特征

基于我国中东部2002—2009年5—9月逐小时降水观测资料和一天四次的NCEP最终分析资料,通过时空匹配处理,得到强度为20~49.9 mm·h-1(A类)、50~79.9 mm·h-1(B类)和不小于80 mm·h-1(C类)的短时强降水天气样本序列,逐类统计分析用于表征其发生发展环境条件的水汽、热力、抬升触发和垂直风切变等物理量的分布特征。结果表明:表征水汽条件的大气可降水量(TPW)对三类短时强降水有一定的指示意义,A、B、C类短时强降水必要的TPW值分别为27、32、42 mm,短时强降水量越大,其所需水汽含量越高。约50%的三类短时强降水均出现在TPW大于60 mm的湿环境中。表征热力、能量、动力和垂直风切变条件的物理量对三类短时强降水的环境条件区分并不显著,环境大气中水汽多少可能是决定短时强降水级别的必要因素。B类和C类短时强降水的高概率密度区域范围大致为TPW在55~70 mm之间、0—6 km垂直风切变在5~15 m·s-1之间,而C类短时强降水在TPW与最佳对流有效位能(BCAPE)以及0—6 km垂直风切变与BCAPE的概率密度分布图中均有两个显著高概率密度区,可能与CAPE影响高级别短时强降水产生的两种机制有关。     

基于物理量参数的伊犁河谷短时强降水预报技术研究

利用伊犁河谷2010～2018年6～8月68个短时强降水天气过程样本,采用箱线图的形式讨论产生短时强降水的关键环境参数的阈值,并对短时强降水天气过程的关键环境参数月特征进行了讨论,最后对2019所夏季的短时强降水天气过程进行检验。结果表明：(1)K指数、修正K指数、瑞士第二雷暴指数、对流凝结高度、Teffer指数、大风指数、对流温度、对流凝结高度处温度、总指数、整层比湿积分与产生降水的相关系数达到0.30以上,对降水有较好的指示意义,其中整层比湿积分的相关系数最高,达到0.465。(2)17个物理量参数涵盖75%以上降水天气过程的阈值在无降水天气过程中的概率,Charbr修正K指数(ChTTK)指示意义最好,概率只有16.8%,而干暖盖指数(Ls)、特征层高度中的对流凝结高度到50%以上,对出现降水的指示性较差。最终选取Charbr修正K指数、K指数、mK指数、Teffer指数、瑞士第二雷暴指数、整层比湿积分这6个关键环境参数。(3)6个环境参数的阈值落在降水天气过程的概率都小于25%,瑞士第二雷暴指数指示意义最好,仅为10.7%。(４)6月份的mK指数、K指数、Charba修正K指数的阈值分别为32、38和36℃；7月份的mK指数、K指数、Charba修正K指数的阈值分别为31、37和35℃；8月份的mK指数、K指数、Charba修正K指数的阈值分别为32、38和37℃。6、7、8月份Teffer指数产生短时强降水的阈值,分别为43、47和43℃。瑞士第二雷暴指数(SWISS12)6、7、8月份的阈值分别为3.4、4.3、3.6。整层比湿积分6、7、8月的阈值,分别为2320 g.kg_^-1,2390 g.kg_^-1、2392 g.kg_^-1。(5)对2019年6-8月的降水天气过程及短时强降水天气过程进行检验评估,降水预报正确的样本为43个,漏报为41个,空报7个。准确率为(Ts)47.3%。短时强降水样本的检验,漏报率6、7、8三个月都为50%,空报率7月份最高,为71.4%,而8月份没有空报。准确率(Ts)是8月份最高(50%),6月份次之(33.3%),7月份最低(20%)。     

四川盆地不同强度短时强降水物理量特征对比分析

利用2007—2017年5—9月四川盆地84个国家自动站逐小时观测资料和时间间隔6 h的ERA-Interim再分析资料,分析了四川盆地不同强度短时强降水发生发展所需的热力、水汽和垂直风切变等条件,并对不同强度短时强降水的环境物理量特征进行了对比。结果表明,极端短时强降水的抬升凝结高度、自由对流高度和平衡高度(EL)均高于普通短时强降水,EL可以较好地区分极端短时强降水和普通短时强降水,约75%的极端短时强降水和普通短时强降水分别发生在EL高于258.6和658.2 hPa的环境下。极端短时强降水的对流有效位能(CAPE)和对流抑制能量值同样高于普通短时强降水,约50%的极端短时强降水和普通短时强降水的CAPE值分别高于792.5和451.9 J·kg~(-1)。不同强度短时强降水的850和500 hPa假相当位温差(θ_(se850)-θ_(se500))差异显著,极端短时强降水的θ_(se850)-θ_(se500)数值明显高于普通短时强降水,10℃可做为区分二者的参考阈值。约50%的短时强降水大气整层可降水量(PW)超过58 mm,不同强度短时强降水的PW差异不明显,但极端短时强降水具有较为明显的上干下湿垂直分布特征。垂直风切变和上升运动对四川盆地不同强度短时强降水的区分没有明确的指示意义。     

锋生切变型强对流概念模型在浙江中西部“3·21”过程中的应用探究

利用ECMWF 0.25°×0.25°再分析资料,对照浙中西的强对流概念模型,对2019年3月21日发生在浙江中西部地区(简称"浙中西")的一次雷暴大风为主的强对流过程(简称"3·21"过程)进行诊断分析、经验总结。结果表明:该过程符合浙中西锋生切变型的强对流概念模型,出现该过程的环境条件是700 hPa西南急流脉动、850 hPa偏北和偏南两支气流强烈发展、地面低压倒槽和低层湿舌增强;探空曲线表现为上干下湿,对流层中层有明显的干侵入,大风指数I_w、对流有效位能 (Convective Available Potential Energy, CAPE)和500 hPa以下垂直风切变异常偏强形成动力强迫;对比不同强对流天气有不同的预报着眼点,设定阈值或可提高预报警报效率,如雷暴大风天气大风指数I_w > 18.5 m·s^-1、CAPE> 1 700 J·kg^-1、500 hPa的相对湿度小于46 %,冰雹天气则0 ℃层、-20 ℃层高度低于4.6 km和7.6 km且850 hPa与500 hPa气层温差高于26 ℃等,深刻理解该类强对流概念模型,是做好此类致灾性强对流潜势预报的关键点。     

丰都县强对流天气特征分析

该文利用2005-2014年丰都县地面天气、探空数据、NCEP 1°×1°FNL再分析资料等,对丰都地区冰雹、雷暴大风、短时强降水这3类强对流天气特征进行统计分析,得出这3类强对流天气的时空分布特征,并从天气个例出发,利用实况资料对强对流天气的差异进行分析,为强对流天气的预警预报提供参考。得到如下结果:短时强降水通常出现在5-9月,大风通常出现在5—8月,冰雹通常出现南部的七跃山脉和北部的蒋家山和黄草山脉附近~([1]),2005—2014年间共出现了7次,3—8月均有发生。通过计算3种强对流天气环境场参量,归纳出3种物理量参数的差异:大气可降水量、AT500-T850,K指数、抬升指数(LI)、相对湿度、散度场分布等在冰雹、短时强降水和大风天气中有明显的差异,冰雹和短时强降水的AT500-T850相差了近5℃,大风天气的值介于冰雹和短时强降水之间。大气可降水量分布上,短时强降水的大气可降水量(PW)平均值为58 mm,比冰雹值大约多了10 mm,比大风值多了14 mm。短时强降水出现时几乎整层都是处于饱和的状态,冰雹和大风天气几乎只在中低层有较饱和的水汽,而高层的相对湿度平均值在40%～50%左右。对流指数方面,K指数和LI指数都很好的指示了强对流天气的发生,K指数在短时强降水发生时其平均值在39.8℃左右,较冰雹和大风分别高1.6℃和3℃。短时强降水出现环流位置大多位于600 hPa以下,而冰雹则在300 hPa左右,大风在400 hPa左右。     

江西四次飑线雷达回波和风廓线产品特征分析

为了做好江西飑线天气的监测预警,使用MICAPS系统平台探空资料、江西地面要素资料、江西WebGIS雷达拼图和风廓线雷达产品等资料,对2017～2020年5月江西四次飑线过程进行分析,结果表明：(1)500 hPa低槽、冷锋、倒槽或辐合线,850 hPa至925 hPa切变线、低空西南急流、“上干下湿”不稳定层结、200 hPa分流区,导致江西飑线天气。(2)≥17.2 m/s 的雷暴大风出现有2～23站次,≥50.0 mm 的强降水出现有3～13站次,分别在江西境内各区域出现；飑线天气过程单点最大风速达到27.9 m/s(铅山),单点最大日降水量162.9 mm(资溪)。(3)温度层结曲线与露点曲线近似成“漏斗状”配置,整个大气层结呈上干下湿分布；湿对流有效位温(CAPE )为1124 J/kg,K 指数(K )为39℃,沙氏指数(SI )为－1.94,风暴强度指数(SSI )为274,500-1000(925)hPa垂直风切变(W_500-1000)为11 m/s,零度温度层高度(ZH )为4 970 m,-20度温度层高度(-20H )为8 304 m。(4)雷达拼图上,初始阶段的A回波带和B雷暴回波群的合并,是发展形成飑线的关键；回波带某段向前突出形成的“弓状”回波带结构,是江西飑线回波带强盛阶段的经典形态；飑线回波带上常伴有超级单体和强单体回波出现,且雷电分布密集,最大回波CR强度达到60 dBz以上,地面雷暴大风发生在这些强回波移动前方。(5)风廓线雷达产品上,飑线过境前,边界层风向不统一,边界层以上风向为一致的西南风,垂直速度W 和大气折射指数Cn^₂ 都比较小。飑线过境时,风向转为西南风,垂直速度W 明显加大到 4～8 m/s,大气折射指数Cn^₂ 加大到 -16～-12 m^_-2/3。飑线过境后,慢慢恢复到前期水平。这些研究结果为飑线天气的监测预警提供了依据。     

遵义市夏季短时强降水时空特征分析

本文利用遵义市2016-2020年夏季逐时降水资料和ERA5再分析资料,分析遵义市夏季短时强降水的时空分布特征,并统计午后和后半夜前发生短时强降水的物理量特征,得到以下结论：（1）遵义市夏季短时强降水日变化呈现双锋结构,夜间的峰值主要发生在6月,白天峰值贡献主要来自7-8月。6月和7月的短时强降水是夜间多于白天,而8月则是白天多于夜间,且多为午后强对流。遵义市夏季短时强降水夜间出现异常值概率的大于白天。（2）有6个县的夜雨均值明显高于昼雨,且在昼雨的1倍以上,仅有凤冈和湄潭的夜雨均值低于昼雨均值,7个县日变化双峰结构较为明显,仁怀有明显的4峰结构,可能与我市西高东低的地形分布有关。（3）遵义市夏季短时强降水在西部、北部地区发生短时强降水的概率较高,西部主要集中在河谷地带,北部主要集中在娄山山脉,短时强降水平均站次6-8月逐渐减少,10站次以上站点逐渐北推且减少,可能与副高西伸北抬有关。（4）高海拔站点午后短时强降水对CAPE、K、LI要求更低,低海拔站点需要更好的抬升和中低层暖湿条件,850hPa与500hPa温差则是高海拔站点高于低海拔站点。（5）与14时相比,后半夜发生短时强降水对CAPE、LI、T850-500等要求变低,且抬升指数有4个站均值高于0℃,指示意义没有午后好,后半夜短时强降水K指数的要求变高,大气可降水量要求也是变高的,但主要是高海拔站点变高。     

豫东地区短时强降水时空分布特征及物理量指标分析

利用1985-2018年汛期(5-9月)豫东地区20个国家站小时降水资料和2011-2018年同期豫东地区区域自动站观测数据、NCEP(1°×1°)再分析资料、高空地面观测资料等,统计分析了该区域小时雨强分别≥20mm/h、≥30mm/h和≥50mm/h的短时强降水时空分布特征,结果发现:豫东地区近34年汛期平均年降水量为458.9～577.5 mm/a,短时强降水次数为72.8次/a;2000年是短时强降水多发年份,≥20mm/h的雨强出现158次,是常年平均次数的1.17倍;主汛期的7-8月是不同强度短时强降水多发时期,34年来共计发生≥20mm/h的短时强降水1821次,占同强度短时强降水总次数(2476次)的近74.0%;在短时强降水的日变化中,05时是不同强度短时强降水多发时段,20时为次多发时段。对不同环流背景影响下短时强降水过程的水汽、动力、热力及能量等物理量作统计分析,低槽型短时强降水过程的动力条件优于其他两个类型的,850hPa涡度平均值达3.8×10~(-5)s~(-1),700hPa垂直速度平均值达-0.36 Pa·s~(-1);副高边缘型短时强降水过程不稳定能量条件优势显著,850hPa假相当位温平均值达354.1 K,500-850hPa假相当位温差的平均值达-17.80℃,K指数平均值为38.1℃、CAPE值平均值为2075.0 J·kg~(-1);而台风倒槽型短时强降水过程则在水汽输送方面更具优势,850 hPa比湿平均值为15.5g·kg~(-1),整层可降水量达70.0 mm。     

黔东南地区短时强降水时空分布特征分析

为进一步分析研究黔东南地区短时强降水的时空分布特征,更好地指导短时强降水预报预警业务工作,利用2015—2021年黔东南地区16个国家自动气象站和410个区域自动气象站逐小时降水资料,对≥20 mm·h^-1短时强降水的时空变化特征进行统计分析。结果表明：（1）黔东南短时强降水频次有逐年增加趋势,[20,40) mm·h^-1量级的短时强降水年际变化相对较小,其余量级年际变化较大。（2）短时强降水主要出现在主汛期4—9月,6月最多,5月次之;年际变化相对较小的是5月、6月、7月和8月,各月短时强降水量级均以[20,40) mm·h^-1量级最多,主要出现在5—8月,以6月出现频次最高。（3）短时强降水主要以[20,80) mm·h^-1量级为主,且日变化频次均呈双峰形势,以傍晚至凌晨时段出现最多,中午前后出现的频次次之,具有夜间发生的显著特征。（4）短时强降水空间分布呈南多北少特征,短时强降水高发区与雷公山、月亮山迎风坡、喇叭口等特殊地形的强迫抬升作用密切相关。     

利用探空资料确定呼和浩特地区3类强对流天气预警阈值

利用呼和浩特探空站计算的16个物理量,分析了2012—2016年6—8月呼和浩特地区的冰雹、雷暴大风及短时强降水天气过程中各物理量差异,结果表明:①订正后的(对流有效位能)CAPE大于等于1000J·kg-1、0℃层高度约4200m左右,-20℃层约在7200m左右,500hPa和850hPa温差达-25℃,逆温层高度在2km以上基本可以判定为冰雹天气;②短时强降水对水汽的依赖度更高,且具有更强的热力不稳定性,低层的温度露点差、500hPa与850hPa的假相当位温差Δθse(500-850)、大气可降水量PW也是短时强降水天气的重要判据;③订正后的(下沿对流有效位能)DCAPE值雷暴大风明显大于冰雹和短时强降水,约为其他2类强对流天气的2倍,订正后的CAPE略小于其他2类强对流天气。根据四分位数法、所占比例≥70%以及均值法界定各类预报因子阈值大小,进而确立了呼和浩特地区强对流天气预警指标。经检验均值法确定的阈值指标命中率均达到50%以上,可参考价值较高。     

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.