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。     

2017年2月大气环流和天气分析

2017年2月大气环流的主要特征是极涡偏强且呈单极偏心型分布,中高纬环流呈3波型,西太平洋副热带高压强度接近常年,南支槽强度较常年偏弱。2月全国平均气温0℃,较常年同期偏高1.7℃;全国平均降水量14.4 mm,比常年同期（17.4 mm）偏少17.1%。2月我国有两次强冷空气过程;3次降水过程,其中新疆出现了一次暴雪过程,日降水量打破历史极值;中东部出现两次雾 霾天气。     

2019年1月大气环流和天气分析

2019年1月大气环流主要特征为：北半球极涡呈偶极型分布,环流呈三波型,南支槽平均位置大致位于90°E附近,同时,西太平洋副热带高压较常年同期位置偏西,强度偏强。本月,全国平均降水量为14.0 mm,较常年同期（13.5 mm）偏多4%,月内出现三次较强降水过程,江南和西南部分地区降水明显,全国共有35站日降水量达到极端事件标准。全国平均气温为-4.1℃,较常年同期（-5.0℃）偏高0.9℃,共出现4次冷空气过程。本月共发生2次大范围雾 霾天气过程。     

2021年1月大气环流和天气分析

2021年1月大气环流的主要特征是:北半球极涡呈偶极型分布,欧亚中高纬度环流经向度大,东亚大槽偏西偏强,南支槽偏弱。1月,全国平均降水量为5.6 mm,比常年同期(13.2 mm)偏少58%,为1961年以来第四少;全国平均气温为-4.5℃,比常年同期(-5.0℃)偏高0.5℃。月内降水偏少,共出现1次强冷空气过程、2次沙尘天气过程和1次大范围持续性雾-霾天气过程。其中4—7日,我国中东部地区遭遇的强冷空气过程具有影响范围广、华北黄淮低温极端性显著、大风持续时间长等特点。     

2020年12月大气环流和天气分析

2020年12月大气环流的主要特征是:北半球极涡呈偶极分布,环流呈三波型,欧亚中高纬度环流经向度大,东亚大槽偏强,南支槽偏弱。12月,全国平均降水量为5.8 mm,比常年同期(10.5 mm)偏少45.3%,全国平均气温为-3.9℃,比常年同期(-3.2℃)偏低0.7℃。月内共出现2次强冷空气过程、2次大范围降水过程和2次大范围雾-霾天气过程。其中27—31日,我国大部分地区遭遇寒潮天气,降温幅度大,影响范围广,多地最低气温突破历史极值。     

2022年11月大气环流和天气分析

2022年11月大气环流的主要特征是:北半球极涡呈偶极型,东亚大槽偏弱,南支槽偏弱,副热带高压偏强。11月,全国平均降水为26.9 mm,比常年同期(20.2 mm)偏多33.2%;全国平均气温为4.8℃,较常年同期(3.3℃)偏高1.5℃。月内气温冷暖起伏较大,前中期冷空气活动偏弱,大部地区气温偏高,降水偏少;后期受强冷空气、活跃南支槽影响,气温大幅降低,降水显著增多。月内出现了1次全国型寒潮过程,影响范围广、降温幅度大,以及2次大范围持续性雾-霾天气过程。     

2016年1月大气环流和天气分析

2016年1月大气环流主要特征为：北半球共有三个极涡中心,强度较常年同期偏强,欧亚中高纬环流经向度大,东亚大槽和南支槽均偏强。1月,全国平均降水量25.7 mm,较常年同期偏多94.7%,广东、广西和湖南三省(区)平均降水量偏多3.7倍,为1951年以来同期第一多。1月,全国平均气温-5.3℃,较常年同期（-5.0℃）偏低0.3℃,冷空气和降水活动频繁,共有5次降水过程和4次寒潮过程,其中,1月21—25日,我国大部地区遭受强寒潮天气。此次过程降温幅度大,影响范围广,多地最低气温跌破历史极值。1月28—29日,南方出现历史同期罕见的强暴雨天气过程。     

2021年3月大气环流和天气分析

2021年3月大气环流呈双极型分布,中高纬环流为三波型,东亚大槽偏弱,西太平洋副热带高压强度与常年相当。3月全国平均气温为6.6℃,较常年同期(4.1℃)偏高2.5℃,为1961年以来同期第二高。全国降水量为27.8 mm,较常年同期(29.5 mm)偏少6%。本月有3次大范围沙尘天气过程,较常年偏强偏多,其中13—18日为近十年我国最强沙尘天气过程。强对流天气偏少,仅月底在长江流域发生一次强对流天气过程。月内冷空气偏弱,仅于15—17日发生一次中等强度冷空气过程。云南等地干旱持续,华南干旱开始发展。     

2018年3月大气环流和天气分析

2018年3月大气环流的主要特征是极涡呈偶极型分布,中高纬环流呈3波型,西太平洋副热带高压强度较常年偏弱,南支槽强度与常年相当。3月全国平均气温7.0℃,较常年同期（4.1℃）偏高2.9℃,为1961年以来同期最高;全国平均降水量29.4 mm,接近常年同期（29.5 mm）。月内我国中东部地区出现1次全国中等（南方强）冷空气过程,1次北方强冷空气过程;南方地区有5次主要降水过程;北方地区有3次沙尘天气过程;江西、湖北、湖南和广西等省(区)局地遭受风雹袭击。     

2020年11月大气环流和天气分析

2020年11月大气环流的主要特征为:北半球极涡呈偶极分布,环流呈三波型,东亚大槽偏弱,南支槽偏弱,西太平洋副热带高压偏西偏强。全国平均降水量为16.9 mm,比常年同期(19.0 mm)偏少11%,月内17—19日出现了一次强雨雪天气过程,湖北恩施建始县和辽宁丹东出现大暴雨,黑龙江牡丹江、鸡西和七台河、内蒙古通辽和赤峰等地出现大暴雪或特大暴雪。全国平均气温为3.9℃,比常年同期(2.9℃)偏高1℃,11月共出现4次冷空气过程,其中1次为全国强冷空气过程(18—22日)。10—17日,大气扩散条件较为不利,华北中南部、黄淮西部、汾渭平原等地发生一次雾-霾天气过程。     

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