2018年9月大气环流和天气分析

2018年9月大气环流的主要特征是：极涡呈偶极型,中高纬地区西风带为多波型分布,西太平洋副高强度较常年偏弱、位置偏西。全国平均降水量74.2 mm,较常年同期(65.3 mm)偏多14%;全国平均气温为16.7℃,较常年同期(16.6℃)偏高0.1℃。9月我国大范围的降水有3次,华南和西北地区东部等地出现强降水,局地灾情严重。9月在西北太平洋和南海共有4个台风生成,其中1822号台风山竹和1823号台风百里嘉在我国广东省登陆。月内黑龙江遭受低温冷冻灾害;华西秋雨开始偏晚,云南、四川南部、重庆和贵州南部秋雨强度总体偏强。     

2019年9月大气环流和天气分析

2019年9月环流特征如下:北半球极涡呈单极型分布,强度偏弱;亚洲大陆中高纬为两槽一脊型;西北太平洋副热带高压明显偏西、偏强。9月全国平均降水量62.4 mm,较常年同期(65.3 mm)偏少4%;全国平均气温为17.7℃,较常年同期(16.6℃)偏高1.1℃。月内共出现了4次主要的区域性强降水过程,其中2次降水活动与台风有关。共有6个台风在西北太平洋和南海海域活动,无台风登陆我国。月内,华西秋雨南区开始偏早,影响显著;长江中下游气象干旱持续发展;江南、华南北部和华北部分地区出现高温天气;黑龙江、内蒙占等多地遭受风雹灾害;黑龙江和内蒙古部分地区遭低温冷冻灾害。     

2016年8月大气环流和天气分析

2016年8月环流特征如下：北半球极涡呈单极型分布,强度偏强;亚洲大陆中、高纬为两槽一脊型;西北太平洋副热带高压位置明显偏东偏北、强度偏弱,大陆高压偏强。8月全国平均降水93.9 mm,较常年同期（105.7 mm）偏少11.2%;全国平均气温22℃,较常年同期（20.8℃）偏高1.2℃,为1961年以来历史同期最高,全国大部地区气温偏高。月内共出现了6次主要的区域性强降水过程,其中4次是由热带气旋或热带辐合带活动引起。8月共有8个热带气旋（风力8级以上）在西北太平洋和南海海域活动,其中1604号台风妮妲和1608号台风电母登陆华南沿海。月内,我国中东部地区出现大范围持续高温天气,东北地区西部和内蒙古东部气象干旱持续。     

2010年9月大气环流和天气分析

2010年9月大气环流主要特征如下:北半球极区呈单极涡型,中高纬地区环流呈4波型分布,冰岛东部上空500hPa高度场有120 gpm正距平;西北太平洋副热带高压强度偏强,西脊点位于24°N、100°E附近,比常年偏西偏北。2010年9月全国平均气温17.1℃,比常年偏高1.1℃;全国降水量为85.1 mm,比常年同期偏多19.7 mm。月内出现了3次较明显的冷空气过程和7次降水过程,有4个台风生成,分别名为"玛瑙"、"莫兰蒂"、"凡亚比"和"马勒卡",其中"莫兰蒂"和"凡亚比"登陆我国,造成重大灾害。     

2017年8月大气环流和天气分析

2017年8月北半球500 hPa极涡呈单极型分布,强度强于常年同期;亚欧洲大陆中高纬为多波动;西北太平洋副热带高压位置偏西,强度接近常年略偏强。8月全国平均降水量126.6 mm,较常年同期（105.3 mm）偏多20%;全国平均气温为21.4℃,较常年同期（20.8℃）偏高0.6℃。月内共出现了8次主要的区域性强降水过程,多站日降水量超历史同期极值。8月共有5个台风在西北太平洋和南海海域活动,其中1713号台风天鸽、1714号台风帕卡4天内先后登陆珠三角。月内,我国南方地区出现大范围持续高温天气,江淮、江汉等地出现阶段性伏旱。     

2023年9月大气环流和天气分析

2023年9月北半球大气环流的主要特征为极涡呈单极型偏向东半球,强度与常年相当,贝加尔湖以西的欧亚中高纬度环流经向度较大,西太平洋副热带高压较常年明显偏西偏强;我国北方大部地区受平直西风环流影响,而南方大部则受西太平洋副热带高压控制。9月,全国平均气温为18.2℃,较常年同期(16.9℃)偏高1.3℃,江南、华南等地出现高温天气;全国平均降水量为69.1 mm,较常年同期(65.3 mm)偏多5.8%。西北太平洋和南海有2个台风生成,较常年同期偏少;另有台风苏拉和海葵登陆我国,接连影响华南导致极端强降水,登陆个数接近常年同期。全国共出现6次大范围较强降水过程及2次强对流天气过程,江苏宿迁、盐城遭受多个强龙卷风袭击。     

2018年8月大气环流和天气分析

2018年8月大气环流的主要特征是极涡呈单极型分布且强度偏强,亚欧洲大陆中高纬为多波型,西北太平洋副热带高压西脊点偏西,强度接近常年略偏强。8月全国平均气温21.9℃,较常年同期偏高1.1℃,为1961年以来历史同期第四高;全国平均降水量127.7 mm,比常年同期（105.3 mm）偏多21.3%,与历史同期相比呈现中部偏少的分布特征。月内我国有11次区域性暴雨天气过程,多站出现极端日降水量。8月共有10个热带气旋在西北太平洋和南海活动,其中1812号台风云雀、1814号台风摩羯、1816号台风贝碧嘉、1818号台风温比亚登陆,生成和登陆个数较常年偏多。我国中东部出现持续性高温天气,同时强对流天气频发,影响范围较广。     

2017年9月大气环流和天气分析

2017年9月大气环流的主要特征是极涡强度接近常年,欧亚大陆中高纬环流呈多波型,西太平洋副热带高压明显偏西偏南,强度接近常年。9月全国平均降水量62.0 mm,较常年同期（65.3 mm）偏少5%;全国平均气温为17.8℃,较常年同期偏高1.2℃,为1961年以来第一高。月内主要出现了10次区域性强降水过程。9月在西北太平洋和南海共有4个台风生成,其中1716号台风“玛娃”在我国广东省登陆。月内四川、云南部分地区秋雨明显,全国13个省（市、区）遭受风雹灾害,内蒙古中东部旱情持续缓和。     

2019年8月大气环流和天气分析

2019年8月,北半球极涡呈单极型分布,强度偏强;亚洲大陆中高纬为两槽一脊型;西北太平洋副热带高压明显偏北,大陆高压偏强。8月全国平均降水量为110.5 mm,较常年同期(105.3 mm)偏多5.0%;全国平均气温为21.6℃,较常年同期(20.8℃)偏高0.8℃。月内共出现了5次主要的区域性强降水过程,其中3次降水活动与台风有关。8月共有6个热带气旋(风力8级以上)在西北太平洋和南海海域活动,其中"韦帕"、"利奇马"、"白鹿"共3个台风登陆我国。月内,东北及四川等地遭受暴雨洪涝灾害;长江中下游气象干旱发展;南方出现大范围持续高温天气;多省(区、市)遭受风雹袭击,部分地区受灾较重。     

2015年9月大气环流和天气分析

2015年9月环流特征如下：北半球高纬地区极涡为单极型,中高纬地区为3波型分布,西北太平洋副热带高压偏西且断裂,9月全国平均降水量为72.4 mm,比常年同期（65.3 mm）偏多14.0%;全国9月平均气温为16.9℃,较常年同期(16.6℃)偏高0.3℃。 月内共有6次强降水过程,24站出现了极端日降水量。西北太平洋和南海有4个台风生成,1517号台风基洛从中太平洋移入,1521号台风杜鹃两次登陆我国并带来大范围降水。西北东部及内蒙古中部等地气象干旱缓解,黄淮大部及辽宁等地气象干旱持续发展。全国多地遭受雷雨大风、冰雹等强对流天气袭击。     

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.     

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.     

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.     

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