2017年3月大气环流和天气分析

2017年3月大气环流的主要特征是极涡偏强且呈单极型分布,中高纬环流呈4波型,西太平洋副热带高压强度较常年偏弱,南支槽强度较常年偏强。3月全国平均气温4.5℃,较常年同期偏高0.4℃;全国平均降水量36.2 mm,比常年同期（29.5 mm）偏多22.7%。月内我国东部地区有2次中等强度冷空气过程;南方地区有3次区域性暴雨天气过程;北方地区有2次沙尘天气过程;江苏、湖南等省局地遭受风雹袭击。     

2018年4月大气环流和天气分析

2018年4月大气环流的主要特征是极涡偏强且呈偶极型分布,中高纬环流呈4波型,西太平洋副热带高压强度较常年偏弱,南支槽强度较常年偏强。4月全国平均气温12.4℃,较常年同期偏高1.4℃;全国平均降水量43.6 mm,比常年同期（44.7 mm）偏少2.5%。月内我国有3次冷空气过程,其中2—7日为一次全国性强冷空气过程,造成大范围剧烈降温和雨雪天气;北方地区出现5次沙尘过程;南方地区出现3次暴雨过程,其中22—24日的暴雨过程给长江中下游地区造成严重的暴雨洪涝灾害。     

2018年6月大气环流和天气分析

2018年6月环流特征如下：北半球高纬地区极涡呈单极型分布且偏强,亚洲中高纬度为两槽一脊环流形势,槽脊强度均强于常年同期;西太平洋副热带高压位置明显偏东,强度略偏强;南海夏季风于6月第二候爆发,较常年偏晚3候且季风槽偏弱。6月全国平均降水量92.9 mm,较常年同期（99.3 mm）偏少6%;全国平均气温为20.9℃,较常年同期（20.0℃）偏高0.9℃。月内共出现4次主要区域性暴雨过程。6月共有3个热带气旋在西北太平洋和南海活动,其中,第四号台风艾云尼3次登陆我国。内蒙古、辽宁、河北北部等地气象干旱持续发展;下旬京津冀地区出现极端高温;全国多个省（区、市）遭受风雹灾害。     

2016年6月大气环流和天气分析

2016年6月环流特征如下：北半球极涡成单极型,中心位于波弗特海北侧附近,较常年同期偏强;中高纬环流呈4波型;西太平洋副热带高压强度较常年同期面积偏大、强度偏强。6月全国平均气温为20.7℃,较常年同期（20.0℃）偏高0.7℃;全国平均降水量为117.0 mm,较常年同期（99.8 mm）偏多17.2%,气温和降水量均为1961年以来第三高值。月内我国出现7次主要的降水过程。江淮、江南北部等地暴雨过程频发,长江中下游地区多地遭受洪涝灾害;华北、黄淮、江淮北部多风雹天气,江苏盐城龙卷风造成严重人员伤亡;月内西北太平洋无台风生成。     

2017年5月大气环流和天气分析

2017年5月大气环流的主要特征是极涡偏强且呈单极型分布,中高纬环流呈多波型,西太平洋副热带高压强度较常年偏强,南支槽强度较常年偏弱。5月全国平均气温17.1℃,较常年同期偏高0.9℃,为1961年以来第4高;全国平均降水量59.4 mm,比常年同期（69.5 mm）偏少14.5%,但5月7日广州出现破历史极值的极端强降水。月内我国南方地区有5次区域性暴雨天气过程;北方出现极端高温过程;东北西部、华北等地发生严重气象干旱;北方地区有2次沙尘天气过程。     

2011年6月大气环流和天气分析

2011年6月环流特征如下：北半球高纬度地区为单一极涡,强度较常年同期偏弱,西太平洋副热带高压较常年偏强,欧亚中高纬环流较平直,多短波槽活动,季风槽较常年略偏弱,槽前西南气流明显。6月,全国平均降水量为102.8mm,比常年同期（97.1mm）偏多5.9%。全国平均气温为20.5℃,比常年同期（19.5℃）偏高1.0℃。月内,我国主要天气气候事件有：长江中下游、华南、西北地区东南部、川渝地区、华北、黄淮、东北南部等地发生暴雨洪涝;有3个热带气旋生成并登陆我国;黄淮等地出现极端高温天气;西北东部、华北、黄淮、江淮北部等地上中旬气象干旱持续发展,下旬干旱缓解;全国23个省（市、区）遭受风雹灾害。     

2013年5月大气环流和天气分析

2013年5月环流特征如下:北半球极涡呈单极型分布,中心强度较常年偏强2～4 dagpm,东亚高纬环流呈4波型分布,其中新西伯利亚地区有一切断低涡,造成了新疆北部的降温天气;南支波动较常年同期活跃,南海季风爆发较常年同期偏早,副热带高压逐步西伸北抬.5月,全国平均气温为16.9℃,较常年同期(16.2℃)偏高0.7℃;全国平均降水量为85.5 mm,较常年同期(69.5 mm)偏多23.0％,为1961年以来历史同期第二多.月内,我国主要天气特点是:南方暴雨频发,20个省市遭受风雹袭击,北方地区出现一次沙尘天气.     

2019年3月大气环流和天气分析

2019年3月大气环流的主要特征是极涡偏强且呈单极型分布,中高纬环流呈三波型分布,东亚槽偏东偏弱,导致弱冷空气频繁影响我国且路径偏东,西太平洋副热带高压强度较常年偏强,南支槽强度较常年偏弱但短波活跃,与频繁南下的东路冷空气交汇造成江南华南降雨显著偏多。3月全国平均气温为5.6℃,较常年同期（4.1℃）偏高1.5℃;全国平均降水量为30.0 mm,接近常年同期（29.5 mm）。月内我国出现1次全国强冷空气过程;南方地区有7次区域性暴雨天气过程;北方地区有1次沙尘天气过程;3月强对流天气过程频繁,江西、广东、广西、湖南等省(区)多地遭受风雹袭击。     

2017年4月大气环流和天气分析

2017年4月大气环流的主要特征是极涡呈偶极型分布,强度偏弱,中高纬环流呈4波型分布,西太平洋副热带高压强度较常年偏强,南支槽强度与常年相当。4月全国平均气温为12.0℃,较常年同期偏高1.0℃;全国平均降水量为44.0 mm,较常年同期偏少2%。月内出现1次全国大范围较强冷空气过程;南方多降水天气,共出现3次区域性暴雨天气;北方出现2次扬沙天气;多省(区、市)局地遭遇风雹灾害。     

2020年2月大气环流和天气分析

2020年2月大气环流的主要特征是北半球极涡呈偶极型分布且较常年同期明显偏强,欧亚地区中高纬环流呈三波型,环流呈纬向型,经向度较小。西太平洋副热带高压较常年偏强;下旬南支槽趋于活跃。2月,我国冷空气过程较常年偏少,出现今年首个全国型寒潮过程;全国平均气温为-0.1℃,较常年同期偏高1.6℃;全国平均降水量21.1 mm,较常年同期偏多18%。此外,前半月中东部多过程性雾 霾天气;西北地区出现今年首次沙尘天气过程。     

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.     

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.     

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正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.SUBMISSIONAll submitted     

A Brief Introduction to Marine Meteorological Science Experiment Base at Bohe Town,Maoming City,Guangdong Province

<正>With the support of specialized funds for national science institutions,the Guangzhou Institute of Tropical and Marine Meteorology,China Meteorological Administration set up in October 2008 an experiment base for marine meteorology and a number of observation systems for the coastal boundary layer,air-sea flux,marine environmental elements,and basic meteorological elements at Bohe town,Maoming city,Guangdong province,in the northern part of the South China Sea.     

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 AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences