广东2月“冷干”和“暖干”年代际特征对比及其与海温异常的联系

根据1961—2019年广东86个站点的降水和气温以及大气环流和海温资料,采用统计分析方法,研究广东2月降水和气温的时空分布特征及其相应的大气环流与海温特征。结果表明:近59年广东2月有两个年代际降水偏少时段,但对应的气温特征显著不同,分别是1961—1981年“冷干”和1999—2019年“暖干”,其对应的大气环流特征表明,第一时段1961—1981年（第二时段1999—2019年）500 hPa高度场以经向（纬向）环流为主,东亚大槽偏强（弱）,东亚冬季风偏强（弱）,低层受异常北（南）风控制,地面冷高压偏强（弱）,偏强的冷空气阻碍了来自海上的水汽输送（偏弱的冷空气不能南下至广东）,使得广东处于水汽辐散区（青藏高原表现为反气旋式环流,南支系统不活跃,对广东地区水汽输送不足）,最终导致广东2月低温少雨（高温少雨）。进一步的分析表明,热带东太平洋和北太平洋中部海温异常是影响广东2月降水的重要外强迫因子,其中第一时段1961—1981年（第二时段1999—2019年）是热带东太平洋（北太平洋中部）海温异常偏冷（暖）通过850 hPa经向风切变偏弱（北太平洋中部异常反气旋环流）来影响广东降水。热带印度洋全区一致型、西太平洋暖池区和北太平洋中部海温异常是影响广东2月气温的外强迫因子,其中前两者主要通过东亚大槽这一环流影响广东气温,而北太平洋中部海温仅影响“暖干”期下广东2月的气温。      

湘中雨季结束日期的异常与前期大气环流和海温的关系

利用1961-2009年NCEP/NCAR再分析资料及ERSST-v3海温资料,研究了湘中雨季结束日期的变化特征及其与前期大气环流和海温的关系.结果表明,近49 a湘中雨季结束日期具有较显著的年际和年代际变化特征,呈2.6天/10a的较显著变晚趋势.湘中雨季结束偏早(晚)年在大气环流上的前兆信号表现为前期冬春季北半球副热带高压、鄂霍茨克海高压和阿留申低压强度弱(强),东亚大槽较浅(深),冷空气活动偏弱(强).前期冬春季中东赤道及以北太平洋和印度洋海温异常是湘中雨季结束的重要短期气候预测信号,前期冬春季赤道中东太平洋、印度洋区域海温偏低(高),北太平洋区域海温偏高(低),湘中雨季结束日期偏早(晚).     

江苏冬夏季人体舒适度指数异常的背景场研究

利用江苏地区37个气象观测站1980—2009年逐日资料,及同时段美国NCEP/NCAR再分析资料以及北太平洋海温资料,通过合成和遥相关法,研究了当江苏冬、夏季人体舒适度指数（CIHB）出现异常偏高和偏低时,大气环流与北太平洋海温场的基本特征。结果表明：（1）CIHB偏高年较偏低年,冬季,东亚大槽偏浅,冬季风明显偏弱,尤其是北风分量偏弱最为明显,江苏上空下沉气流偏弱,均不利于冷空气东移南压以及向下入侵;夏季,副热带高压偏西、偏强,南亚高压偏东、偏北、偏强,夏季风明显偏强,尤其是南风分量偏强显著,导致往北的暖湿气流强盛,垂直运动总体偏弱,不利于夏季对流活动的发生。（2）冬季,CIHB偏高年中西太平洋的海温高于偏低年,尤其是在我国东部近海的黑潮区,偏暖幅度最为明显,无论是超前相关还是同期相关,西太平洋海温与冬季CIHB都是以正相关为主,其中暖池区的正相关最为显著。     

2017/2018年冬季北半球大气环流特征及对我国天气气候的影响

2017/2018年冬季,东亚冬季风强度较常年同期偏强,西伯利亚高压偏强,季内冬季风强弱转换阶段性特征显著。欧亚中高纬以经向环流为主,乌拉尔山高压脊持续发展,东亚槽位置偏西。冬季冷空气过程频繁,受其影响,冬季东北地区气温显著偏低,而高原和西南地区西部异常偏暖。对2017/2018年冬季东亚冬季风偏强的可能原因分析表明,受北太平洋年代际涛动暖位相的调制作用,2017年秋季开始的La Ni〖AKn~D〗a事件对东亚冬季风的影响相对较弱。而冬季北半球极涡持续偏弱,北大西洋海温持续偏暖,中高纬环流系统异常和海温外强迫的共同作用,是东亚冬季风偏强的重要原因。     

2010年秋、冬季节华北持续性干旱的气候成因分析

利用1951～2011年中国台站观测的逐日降水、温度和美国NCEP/NCAR再分析月平均资料, 本文分析2010年秋、冬季(11月至次年2月)发生在华北地区持续性干旱的大气环流和海温异常特征, 并讨论了北极涛动(AO)和La Ni?a事件对此次干旱事件的影响。分析表明, 2010年发生在华北秋、冬季节的持续性干旱是叠加在降水减少气候趋势之上的一次极端干旱事件, 但本次极端干旱事件主要成因是受到同期较强的AO负位相和La Ni?a事件共同的影响。统计发现:AO的负位相有利于乌拉尔山阻塞高压维持和发展, 而贝加尔湖上空出现负位势高度异常, 导致东亚中高纬度经向环流加强和冷空气向南侵袭。AO负位相可导致贝加尔湖上空气压场偏低并影响冷空气的路径和强度, 进而间接地导致华北地区的干冷气候, 而同期La Ni?a的海温异常分布导致西北太平洋副热带高压偏弱偏南, 抑制了西太平洋水汽向华北地区输送, 从而直接导致该地区的干旱。由于2010年AO负指数和La Ni?a事件较历史干旱年份表现出较强和长时间持续性, 从而导致了锋面位置位于华北以南和华北本次的持续性干旱事件。     

东亚-太平洋遥相关型形成过程与ENSO盛期

利用1961～2000年NCEP/NCAR再分析资料、扩展重建的海表温度资料 (ERSST) 和中国730个站旬降水资料, 采用SVD和扩展SVD (ESVD) 分析、合成分析、相关分析等方法, 在分析中国梅雨期降水与同期大气环流和前期冬季海温之间关系的基础上, 研究了ENSO盛期海温异常导致与长江流域梅雨期降水密切相关的东亚/太平洋 (EAP) 遥相关型形成的过程, 及与ENSO相关的海温和大气环流异常的持续性问题.结果表明, 梅雨期EAP遥相关型的出现与ENSO遥强迫作用有密切关系.联系冬季ENSO和梅雨期EAP遥相关型的关键过程主要有三个: (1) 西北太平洋低纬地区异常反气旋环流的形成和维持, 它在冬季形成后一直可维持到夏季, 使得夏季西北太平洋副热带高压偏南偏强; (2) 东亚大槽持续偏弱, 冷空气活动路径偏北偏东, 使西北太平洋海温呈亲潮区偏冷、黑潮区偏暖的海温分布; (3) PNA遥相关型的持续发展, 使北冰洋地区高度增高.后二者通过局地海气相互作用和大气内部调整过程对初夏鄂霍次克海阻塞形势的形成起重要作用.另外, 持续性分析表明, ENSO年大气环流和海温距平型的持续性要比非ENSO年大得多.在ENSO年大气环流和海温之间存在很强的相互作用耦合关系, ENSO引起的大气环流异常可导致太平洋海温异常, 而海温异常一旦形成反过来又可导致大气环流异常的稳定和维持, 对后期初夏东亚季风和我国天气气候产生明显滞后效应.     

东亚-太平洋遥相关型形成过程与ENSO盛期海温关系的研究

利用1961～2000年NCEP/NCAR再分析资料、扩展重建的海表温度资料(ERSST)和中国730个站旬降水资料,采用SVD和扩展SVD（ESVD）分析、合成分析、相关分析等方法,在分析中国梅雨期降水与同期大气环流和前期冬季海温之间关系的基础上,研究了ENSO盛期海温异常导致与长江流域梅雨期降水密切相关的东亚/太平洋（EAP）遥相关型形成的过程,及与ENSO相关的海温和大气环流异常的持续性问题。结果表明,梅雨期EAP遥相关型的出现与ENSO遥强迫作用有密切关系。联系冬季ENSO和梅雨期EAP遥相关型的关键过程主要有三个:（1）西北太平洋低纬地区异常反气旋环流的形成和维持, 它在冬季形成后一直可维持到夏季,使得夏季西北太平洋副热带高压偏南偏强;（2）东亚大槽持续偏弱,冷空气活动路径偏北偏东,使西北太平洋海温呈亲潮区偏冷、黑潮区偏暖的海温分布; （3）PNA遥相关型的持续发展,使北冰洋地区高度增高。后二者通过局地海气相互作用和大气内部调整过程对初夏鄂霍次克海阻塞形势的形成起重要作用。另外,持续性分析表明,ENSO年大气环流和海温距平型的持续性要比非ENSO年大得多。在ENSO年大气环流和海温之间存在很强的相互作用耦合关系,ENSO引起的大气环流异常可导致太平洋海温异常,而海温异常一旦形成反过来又可导致大气环流异常的稳定和维持,对后期初夏东亚季风和我国天气气候产生明显滞后效应。     

2011年海洋和大气环流异常及对中国气候的影响

本文基于实时和历史观测资料,利用气候统计和气候机理诊断方法,对2011年气候异常及成因进行总结分析。结果表明,全球海洋外源强迫和大气内部动力过程共同作用下的大气环流系统组合异常,是造成2011年中国大部地区降水异常偏少,温度明显偏高,呈现暖干型气候特征的主要原因。具体表现为,拉尼娜事件在2011年夏季短暂中断后,9月再次进入拉尼娜状态;西太平洋副热带高压在5月之前异常偏弱、偏东,致使长江中下游出现严重春旱,之后副热带高压有所加强,尤其在6月异常偏强,使长江中下游地区梅雨量偏多、旱涝急转;秋季副热带高压脊线偏北、中高纬度冷空气活动阶段性活跃,致使华西、黄淮地区秋雨异常偏多;热带印度洋海温演变经历负偶极型海温模态后,夏季转为全区一致型暖海温;2010／2011年东亚冬季风偏强,2011年南海夏季风爆发偏早、结束偏晚,东亚夏季风正常偏弱;西北太平洋和南海热带气旋生成数量处于偏少的年代际时段,2011年热带气旋生成数量偏少。     

2011年夏季气候异常及主要异常事件成因分析

本文对2011年夏季的中国气候及大气环流异常特征进行分析,发现我国总体气温偏高,降水偏少。西北西部、华北南部、江淮至江南一带,西南地区东部等地出现了阶段性的较大范围极端高温天气过程。西南地区东部和广西等地出现严重干旱;而长江下游地区降水显著偏多。进一步对中国气候异常事件的成因分析表明：异常高压的长期维持,孟加拉湾的向北水汽输送偏弱及西太平洋副热带高压位置偏东使其西侧的东南和偏南水汽输送对我国西南地区影响小是导致西南地区严重干旱的大气环流因素;2010年秋季出现的中部型拉尼娜事件可能是西南干旱的一个重要外强迫条件。2011年夏季亚洲极涡偏弱偏小,欧亚中高纬地区经向环流偏强,有利于冷空气南下;同时,中纬度西太平洋地区海温持续偏低而激发反气旋性环流产生,造成西太平洋副高偏大偏强,冷暖气流在长江下游地区交汇造成降水显著偏多。     

重庆地区冬季冷暖变化及其异常成因分析

利用1961—2018年重庆地区34个国家气象站冬季逐月平均气温资料,NCEP/NCAR再分析资料及大气环流指数和海温等资料,分析重庆冬季冷暖变化的时间演变特征及冷冬、暖冬年的异常环流形势。结果表明,近58 a重庆冬季平均气温整体呈增加趋势(约增加0.7℃),且变暖趋势通过α=0.05的显著性检验,增暖突变从1993年开始。重庆冷冬年和暖冬年的环流形势存在明显差异:前期夏、秋季的热带海温场偏冷(暖),冬季海平面气压场上西伯利亚高压偏强(弱),500 hPa高度距平场上欧亚大陆呈明显北高(低)南低(高)分布形势,乌拉尔山高压脊和东亚大槽偏强(弱);同时,西太平洋副热带高压和高原冷高压偏弱(强),印缅槽偏强(弱),导致东亚冬季风偏强(弱),有(不)利于冷空气南下影响重庆地区;印缅槽偏强(弱)导致槽前偏南风偏强(弱),有(不)利于槽前暖湿空气输送和重庆地区降水,这种环流配置导致重庆地区易出现冷(暖)冬。热带印度洋、西北太平洋和南半球赤道中太平洋是影响重庆冬季冷暖的关键海温区,对重庆冬季气温预测具有一定的指示意义。     

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