2017年早春濮阳市一次冰雹过程诊断分析

利用常规地面、高空气象资料,郑州站探空订正资料,濮阳气象站实况资料,濮阳和郑州新一代多普勒雷达资料等,对2017年4月13日下午发生在濮阳市的雷暴大风、冰雹等强对流天气过程进行了综合分析。结果表明:(1)本次强对流天气是在中低层低槽东移,地面辐合线南压等大尺度系统影响下产生的;冰雹发生在低空西南暖湿气流大风速带左侧边缘、高空80m/s偏西风急流核出口区左侧、地面辐合线附近。(2)强对流发生前,华北地区850hPa为暖温度脊,500hPa为冷温度槽,形成有利于强对流天气发生的不稳定层结;850、700hPa干湿区错位叠加及露点锋的存在,说明低层在水平和垂直方向上干湿分布极不均匀。(3)郑州站探空订正资料显示,中等以上强度的垂直风切变,有利于强对流风暴的组织发展,深层的垂直风切变构成了冰雹产生的有利环境条件。(4)多普勒雷达组合反射率因子图上对流单体中心强度达65dBz,有超级单体生成;剖面图上有弱回波区、回波悬垂出现;速度图上有低空和超低空急流、27m/s的风速大值区及低层径向辐合、弱中气旋等;垂直积分液态含水量达63kg/m^2,最大回波顶高13km以上。     

利用探空资料判别北京地区夏季强对流的天气类别

利用北京南郊观象台探空资料计算出的18种物理参量及其时间变量,详细分析了2007年和2008年5-9月冰雹、雷暴大风以及暴雨强对流天气过程下物理量的差异.结果表明:0℃层高度、-20℃层高度、500 hPa和850 hPa温差、逆温层高度、低空风切变能比较显著地区分冰雹和暴雨天气,其σ也比较小;此外850 hPa的温度露点差、500 hPa和850 hPa的θse 差、大气可降水屠PW也足判断强对流类别的重要条件.而对于时间变量来说,CAPE、DCAPE、K指数、500 hPa和850 hPa的θse差、PW、低层的垂直风切变这儿种物理量的6小时变量也能比较好地甄别出冰雹(雷暴大风)和暴雨天气.上述研究结果表明,合理利用探空资料甄别夏季强对流天气的类别是可能的.     

1991-2020年河套灌区强对流天气主要流型及环境参量特征分析

利用常规气象观测资料、区域自动站观测资料及ERA5 再分析资料对河套灌区 1991-2020年542个冰雹个例和281个短时强降水个例主要流型及局地要素特征进行分析。分析结果显示:1、短时强降水天气主要有西西伯利亚低槽(涡)、东北冷涡、蒙古冷涡、西南气流四类流型；冰雹天气主要有新疆低槽(涡)、东北冷涡、中亚低槽(涡)、新疆冷涡四类流型。2、河套灌区短时强降水和冰雹各关键参数预报阈值均有差异,最低阈值的建议值采用箱线图25％百分位值,其中分别为26℃和33℃；K指数均值分别为27 ℃和35 ℃；CAPE均值分别为515 J·kg-1和405 J·kg-1；0～6 km垂直风切变均为7×10-3ｓ-1；0℃层高度高度均值分别为4656 m和4069 m；-20℃层高度高度均值分别为8070 m和7054 m。3、冰雹需要更大的K指数、以及低层强暖空气；同时冰雹有更低的 0℃层高度和-20℃层高度,较低的0℃层高度可以防止冰雹下落过程融化；此外下垫面因子对不同强对流天气的影响程度不同,海拔高度是影响河套灌区冰雹分布的主要因素。     

哈尔滨雷暴大风天气分型和特征参数分析

使用MICAPS天气资料和探空资料,对哈尔滨市2016-2020年5-9月产生的雷暴大风天气以500 hPa天气系统为主进行分型,并统计低层影响系统和地面天气系统出现的比率。然后利用NCEP资料计算各个雷暴大风天气发生前的环境参量,并采用百分位数法统计各型发生时的物理量,以25%分位数为阈值给出临界值。结果表明:(1)哈尔滨市雷暴大风天气分为冷涡型、槽前型和西北气流型。(2)850 hPa与500 hPa温度差≥24℃,CAPE值≥310 J/kg,0-6 km垂直风切变≥10 m/s,地面露点温度≥12℃对于哈尔滨市雷暴大风天气有良好的指示意义。(3)槽前型雷暴大风天气的850 hPa与500 hPa温度差最小,西北气流型个例中高CAPE值并不多;水汽条件并不是制约冷涡型雷暴大风天气发生的重要因素。     

湘西地区高架雷暴类冰雹的基本特征与关键预报因子

利用常规气象观测资料,对2005—2014年湖南省湘西州2—3月高架雷暴类冰雹的时空分布特征、天气系统配置及环境场要素特征等进行统计分析,探讨高架雷暴类冰雹发生发展的物理机制。结果表明,湘西早春时期的高架雷暴类冰雹南部地区多于中北部地区,具有一定的日变化。影响高架雷暴类冰雹的主要天气系统为高空槽、700hPa急流以及冷空气等。潜势预报指标包括:850hPa相对湿度大于等于92%,700hPa相对湿度大于等于60%,500hPa相对湿度小于等于48.5%;850hPa存在强的温度锋区,温差大于等于13℃/5个纬度;700hPa与500hPa的温差大于等于15℃;700hPa有风速大于等于16m·s~(-1)的西南急流,且850hPa与700hPa的垂直风切变大于等于19m·s~(-1);0℃层高度为3~4km,-20℃层高度为6~7km。     

渭河流域2008年1月连阴雪天气过程成因分析

针对2008年6月29日下午到夜间,发生在山西省忻州市神池、五寨、原平等县（市）一带的严重局部冰雹天气过程,利用天气环流形势,各种物理量特征,分析其成因。指出：a）500hPa蒙古东部的冷涡东移,冷空气叠加在850hPa暖脊上,产生上冷下暖的位势不稳定能量。b）前期先导槽的滑过,使低层增湿,潜在不稳定度增大。c）降雹区域沙氏指数、K指数等都符合山西降雹标准。d）850hPa-500hPa有较强垂直风切变,使动力不稳定能量加强,为冰雹天气发生发展提供了必要条件。e）特别是山区由于海拔高,山脉阻挡,气流辐合上升,容易产生局地强对流,诱发雹云生成,出现冰雹天气。     

铜仁市暴雪天气的环流配置及物理量特征分析

铜仁市暴雪发生的频次低,2005年至今仅发生5次,因此准确的量级和落区预报难度较大。本文选取2004-2021年铜仁市出现的5场暴雪天气过程,就大尺度环流形势、高低空天气系统配置和物理量特征进行分析,找出暴雪环流形势以及物理量预报指标。结果显示：铜仁市暴雪发生时,500hPa中高纬为两槽一脊形势,我国东北地区-日本海低槽加深发展,中低纬孟湾附近有南支低槽系统东移;海平面场上贝加尔湖西部冷高中心强度为1060hPa,大于1030hPa的等压线线进入铜仁市。暴雪落区出现在500hPa高空槽和南支槽前、700hPa西南急流左侧或低涡切变线南侧、850hPa东北急流或东北风前部的风速辐合区内。暴雪日500hPa温度平均低于-16℃,700hPa温度为-2～-6℃,850hPa温度-6～-8℃,地面气温为0～-4℃,地面气温越低降雪持续时间越长。暴雪发生时大气中层700～500hPa上升运动明显增强,这可作为降雪增大的预示指标;散度场总体表现为低空辐合、高空辐散的特征,当辐合层次伸展更高时,有利于暴雪天气的持续;水汽通量散度辐合主要在850hPa,平均值为-3.6×10-6﹒g﹒cm-2﹒hPa-1﹒s-1; 500hPa比湿值≥1.5g/kg是暴雪发生的参考指标。     

中国短时强对流天气的若干环境参数特征分析

利用中国2005-2009年2 000多个国家级气象观测站雨量资料和2002-2011年部分探空站探空资料,研究了中国短时强降水、强冰雹、雷暴大风以及混合型强对流天气的环境参数特征,通过环境参数特征的对比分析,将上述四种强对流天气加以区分,并对所选取的探空数据和环境参数进行了分类和对比分析,结果表明:(1)通过T-logp图温湿曲线形态、500～700 hPa和850～500 hPa温差、0℃、20℃层和平衡层高度、地面和1.5 km高度的露点温度、1.5 km高度温度露点差、对流有效位能和0～6 km垂直风切变等区分上述四种类型强对流天气的环境背景;(2)纯粹短时强降水天气(包括1、II型)与强冰雹天气、雷暴大风天气环境参数的区别比较显著,前者与后两者相比主要表现在较小的700～500 hPa和850～500 hPa温差,弱的垂直风切变,较高的0℃层、-20℃层和平衡层高度,较大的地面和地面以上1.5 km处的露点温度,其中短时强降水I型(占了纯粹短时强降水的大多数)以其整层较高的相对湿度与其他类型强对流的环境背景差异最为明显;(3)混合型强天气与强冰雹天气、雷暴大风天气在T-logp图温湿曲线形态、对流有效位能及0～6 km垂直风切变诸方面特征相似,表现为对流层中层存在明显干层、较大的对流有效位能和0～6 km垂直风切变,但在相对较高的平衡层高度、较高地面和地面以上1.5 km处露点温度及较小的850～500hPa温差等方面与纯粹短时强降水更为接近.     

2012年早春广西高架雷暴冰雹天气过程分析

利用常规观测资料和雷达资料,对2012年早春广西高架强雷暴冰雹天气过程进行分析,得出以下结论:(1)冰雹伴随雷暴发生在地面锋后约1000 km,边界层为冷高压控制.850 hPa风速较小,700 hPa以上层有强急流,700～850 hPa有强的垂直风切变,500 hPa高空冷槽东移为对流的发生提供触发条件.(2)冰雹发生在850 hPa切变线南北两侧约200 km范围,等压面锋区强度大;高空槽前正负变温使700～500 hPa垂直方向温度差大,导致层结对流不稳定性加大.当500 hPa低槽移至强锋区上空时,锋面坡度变陡,上升运动加强,不稳定性增大,使得冰胚在对流层中层增长而形成冰雹.(3)风暴追踪信息显示风暴生成高度高,在垂直方向上倾斜增长;质心均在5～6 km,风暴生成后,随着时间的推移逐渐向低层发展,最大反射率以及液态含水量均不大,具有明显高架雷暴特征.     

河南省冰雹天气环境参量特征分析

利用2006—2015年5—9月10a高空、地面观测资料,对河南省冰雹天气过程的500hPa环流形势进行分型,并统计分析冰雹天气环境参量特征。结果表明:河南冰雹天气的500hPa环流形势分为西北气流、华北低涡、低槽和西南气流四种类型,其中西北气流型最多,冰雹过程占总数的55.2%;冰雹天气主要环境参量阈值是对流有效位能≥1137J/kg,850hPa与500hPa温度差≥27℃,850hPa与500hPa假相当位温差≥5.5℃,抬升指数≤-4.5℃,大气整层可降水量≥2.9cm,14时地面露点温度≥16℃。     

COMPARATIVE ANALYSIS OF VARIOUS DATA OF AIR–SEA TEMPERATURE DIFFERENCE AND ITS VARIATION ACROSS SOUTH CHINA SEA IN THE PAST 35 YEARS

Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter.     

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.     

IMPACT OF ATMOSPHERIC LOW-FREQUENCY OSCILLATION ON THE IMMIGRATION OF NILAPARVATA LUGENS(STL) IN HUNAN AND JIANGXI PROVINCES

Various features of the atmospheric environment affect the number of migratory insects, besides their initial population. However, little is known about the impact of atmospheric low-frequency oscillation(10 to 90 days) on insect migration. A case study was conducted to ascertain the influence of low-frequency atmospheric oscillation on the immigration of brown planthopper, Nilaparvata lugens(Stl), in Hunan and Jiangxi provinces. The results showed the following:(1) The number of immigrating N. lugens from April to June of 2007 through 2016 mainly exhibited a periodic oscillation of 10 to 20 days.(2) The 10-20 d low-frequency number of immigrating N. lugens was significantly correlated with a low-frequency wind field and a geopotential height field at 850 h Pa.(3) During the peak phase of immigration, southwest or south winds served as a driving force and carried N. lugens populations northward, and when in the back of the trough and the front of the ridge, the downward airflow created a favorable condition for N. lugens to land in the study area. In conclusion, the northward migration of N. lugens was influenced by a low-frequency atmospheric circulation based on the analysis of dynamics. This study was the first research connecting atmospheric low-frequency oscillation to insect migration.     

A COMPARATIVE ANALYSIS OF ATMOSPHERIC AND OCEANIC CONDITIONS BEFORE THE OCCURRENCE OF TWO TYPES OF EL NIO EVENTS

The atmospheric and oceanic conditions before the onset of EP El Ni?o and CP El Ni?o in nearly 30 years are compared and analyzed by using 850 hPa wind, 20℃ isotherm depth, sea surface temperature and the Wheeler and Hendon index. The results are as follows: In the western equatorial Pacific, the occurrence of the anomalously strong westerly winds of the EP El Ni?o is earlier than that of the CP El Ni?o. Its intensity is far stronger than that of the CP El Ni?o. Two months before the El Ni?o, the anomaly westerly winds of the EP El Ni?o have extended to the eastern Pacific region, while the westerly wind anomaly of the CP El Ni?o can only extend to the west of the dateline three months before the El Ni?o and later stay there. Unlike the EP El Ni?o, the CP El Ni?o is always associated with easterly wind anomaly in the eastern equatorial Pacific before its onset. The thermocline depth anomaly of the EP El Ni?o can significantly move eastward and deepen. In addition, we also find that the evolution of thermocline is ahead of the development of the sea surface temperature for the EP El Ni?o. The strong MJO activity of the EP El Ni?o in the western and central Pacific is earlier than that of the CP El Ni?o. Measured by the standard deviation of the zonal wind square, the intensity of MJO activity of the EP El Ni?o is significantly greater than that of the CP El Ni?o before the onset of El Ni?o.     

Could the Recent Taal Volcano Eruption Trigger an El Ni?o and Lead to Eurasian Warming?

正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment.     

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.     

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.     

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