北半球热带中太平洋与印度洋海表温度梯度对夏季西北太平洋热带气旋生成频数变化的影响     

方珂  余锦华 《热带海洋学报》2019,38(5):42-51

基于1951—2018年哈德里中心海温资料、美国气象环境预报中心和美国国家大气研究中心再分析资料和第四代欧洲中心汉堡模式, 针对1994年、2018年等西北太平洋热带气旋(TC)生成异常多的年份, 研究了引起TC增加的海表温度异常(SSTA)模态及其影响机制。结果表明, 北半球热带中太平洋增暖与印度洋变冷是夏季西北太平洋TC生成频数增加的主要原因, 北大西洋负三极型式SSTA促使TC生成的进一步增加。热带中太平洋增暖与印度洋冷却在菲律宾以东激发出西风异常和气旋性环流异常。北大西洋负三极型式SSTA在我国南海、菲律宾至东南沿岸激发出气旋性环流异常。前者在西北太平洋中部, 后者在南海产生有利于TC生成的局地环境。1994年和2018年夏季热带中太平洋出现暖SSTA、印度洋为冷SSTA、北大西洋呈现负三极型式SSTA, 西北太平洋TC生成频数极端增多。近30年来, 当出现热带中太平洋增暖和印度洋冷却时, 北大西洋表现出比1989年以前更强的负三极型式SSTA, 使西北太平洋TC生成频数和北半球热带印度洋-太平洋SSTA梯度的线性相关更显著。  相似文献   

Classification of yearly extreme precipitation events and associated flood risk in the Yangtze-Huaihe River Valley     

Zhiqing Xie  Yin Du  Yan Zeng  Qian Miao 《中国科学:地球科学(英文版)》2018,61(9):1341-1356

Fifty cases of regional yearly extreme precipitation events(RYEPEs)were identified over the Yangtze-Huaihe River Valley(YHRV)during 1979–2016 applying the statistical percentile method.There were five types of RYEPEs,namely Yangtze Meiyu(YM-RYEPE),Huaihe Meiyu(HM-RYEPE),southwest-northeast-oriented Meiyu(SWNE-RYEPE)and typhoon I and II(TC-RYEPE)types of RYEPEs.Potential vorticity diagnosis showed that propagation trajectories of the RYEPEs along the Western Pacific Subtropical High and its steering flow were concentrated over the southern YHRV.As a result,the strongest and most frequently RYEPEs events,about 16–21 cases with average rainfall above 100 mm,occurred in the southern YHRV,particularly in the Nanjing metropolitan area.There have been 14 cases of flood-inducing RYEPEs since 1979,with the submerged area exceeding 120 km~2as simulated by the Flood Area hydraulic model,comprising six HM-RYEPEs,five YM-RYEPEs,two TC-RYEPEs,and one SWNE-RYEPE.The combination of evolving RYEPEs and rapid expansion of urban agglomeration is most likely to change the flood risk distribution over the Nanjing metropolitan area in the future.In the RCP6.0(RCP8.5)scenario,the built-up area increases at a rate of about 10.41 km~2(10 yr)~(-1)(24.67 km~2(10 yr)~(-1))from 2010 to 2100,and the area of high flood risk correspondingly increases from 3.86 km~2(3.86 km~2)to 9.00 km~2(13.51 km~2).Areas of high flood risk are mainly located at Chishan Lake in Jurong,Lukou International Airport in Nanjing,Dongshan in Jiangning District,Lishui District and other low-lying areas.The accurate simulation of flood scenarios can help reduce losses due to torrential flooding and improve early warnings,evacuation planning and risk analysis.More attention should be paid to the projected high flood risk because of the concentrated population,industrial zones and social wealth throughout the Nanjing metropolitan area.  相似文献   

全球干旱指数研究进展          下载免费PDF全文

宋艳玲 《应用气象学报》2022,33(5):513-526

干旱是世界最严重的气象灾害, 是自然灾害中经济损失最重、影响范围最广的灾害。我国深受干旱灾害的影响, 近几十年干旱事件频繁发生, 给社会造成的不利影响和对人们生存环境的危害日趋严重。因此, 讨论全球干旱指数研究进展对于我国干旱研究及防旱抗旱工作具有重要意义。该文系统介绍全球特别是欧美等国气象干旱指数、农业干旱指数、水文干旱指数、遥感干旱指数以及综合干旱指数研究进展, 并与我国干旱指数研究情况对比。探讨我国在干旱研究领域存在的主要问题, 包括干旱指数适用性比较不足, 新的机理性干旱监测指数研究不足, 干旱预测预警研究不足。因此加强干旱机理机制研究、开展干旱监测准确性定量评估和加强数值模式在干旱预测预警中的应用是未来研究的重点和难点。  相似文献   

“21·7”河南特大暴雨气象和水文雨量观测对比          下载免费PDF全文

宝兴华  夏茹娣  罗亚丽  徐祥德 《应用气象学报》2022,33(6):668-681

2021年“21·7”河南特大暴雨打破我国大陆小时气象观测纪录,该极端天气事件位列2021年中国十大天气气候事件第2位。已有研究使用气象地面站雨量观测资料对此次过程进行雨情分析和极值统计,但降水时空分布不均匀,单一来源资料存在不确定性。通过对比气象站和水文站雨量资料,分析两套业务观测系统记录“21·7”河南特大暴雨过程的异同,发现气象站和水文站雨量在时间和空间分布上具有很好的一致性,两者不同等级的累积降雨落区、逐日和逐时降雨演变趋势均一致性强,但累积雨量和雨强极值的空间分布和数值存在差异,两套资料在暴雨中心（过程雨量大于600 mm）的系统性偏差小于1%。气象站和水文站的融合资料呈现比单一资料更细致的降雨分布、更全面的演变特征。此外,基于融合资料发现累积雨量排名前3位的城市（郑州、鹤壁、新乡）均具有累积雨量大、小时雨强极强、强降雨集中、雨强突然增长的特征,鹤壁和新乡最强降雨时段分别比郑州晚26 h和28 h。  相似文献   

Effects of convective available potential energy,temperature and humidity on the variability of thunderstorm frequency over Bangladesh     

Wahiduzzaman  Md  Ali  Md. Arfan  Luo  Jing-Jia  Wang  Yu  Uddin  Md. Jalal  Shahid  Shamsuddin  Islam  A. R. M. Towfiqul  Mondal  Sanjit Kumar  Siddiki  Ubaydur Rahaman  Bilal  Muhammad  Qiu  Zhongfeng  Dambul  Ramzah  Eibek  Kutubuddin  Haque  Md. Emdadul 《Theoretical and Applied Climatology》2022,147(1-2):325-346

Theoretical and Applied Climatology - The present study examines the effects of convective available potential energy (CAPE), temperature and humidity on the spatiotemporal variation of...  相似文献   

Intraseasonal oscillation of the southwest monsoon over Sri Lanka and evaluation of its subseasonal forecast skill          下载免费PDF全文

L.A.D.Buddika Bandurathna  Lu Wang  Xuan Zhou  Yifeng Cheng  Lin Chen 《大气和海洋科学快报》2021,14(6):7-13

斯里兰卡的雨季发生于5-9月间,主要受西南季风的控制.本文发现该地区的西南季风降水存在很强的次季节变率,主导周期为10-35天.降水的季节内变化与西传的异常气旋有关.进一步,利用S2S比较计划中欧洲中心的数值预报模式(ECMWF)提供的回报试验数据,评估了当今动力模式对斯里兰卡西南季风次季节变化的预报技巧.结果显示,对季风指数的预测技巧超过30天,而对降水指数的预测技巧大约两周,且模式的预报技巧具有明显的年际差异.分析表明,能否正确模拟出大尺度环流对热带对流的响应是影响斯里兰卡降水预测的重要因子.  相似文献   

Intraseasonal oscillation of the rainfall variability over Rwanda and evaluation of its subseasonal forecasting skill          下载免费PDF全文

Xuan Zhou  Lin Chen  Janet Umuhoza  Yifeng Cheng  Lu Wang  Ran Wang 《大气和海洋科学快报》2021,14(6):60-65

非洲中东部地区的经济主要依靠自给农业支撑,该地区农业经济对降水的变化尤为敏感.本文以卢旺达为例,观测分析指出卢旺达的次季节降雨主要集中在10-25天;根据次季节尺度降水变率的单点相关方法,发现卢旺达的次季节降水变率和周围区域变化一致;进一步合成结果显示该地区次季节降水变率与异常西风有关,这可追溯到赤道地区西传的赤道Rossby波.最后,本文评估了当前动力模式ECMWF对 卢旺达地区(即非洲中东部)次季节降水变率的预报能力,发现EC模式在对该区域降水和相关风场指数的预报技巧都在18天左右,且预报技巧表现出一定的年际差异,这可能与热带太平洋的背景海温信号有关.该工作增进了当 前对非洲中东部地区的次季节降水变率和预测水平的认知,并且对该地区国家粮食安全和防灾减灾具有启示性意义.  相似文献   

Trigger mechanism of a snow burst event in Northeast China: 东北一次雪飑事件的触发机制研究          下载免费PDF全文

《大气和海洋科学快报》2021,14(2):100017

A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017, with the snowband generally aligned with a northeast–southwest-oriented cold front. ECMWF reanalysis data were used to diagnose the possible trigger mechanism. Results showed there were two stages: (a) an initial stage far away from the Changbai Mountains, and (b) an enhancement stage under the influence of high terrain. During the initial stage, the coupling of low-level frontogenesis and a favorable convergence pattern caused strong upward motion, contributing to the release of instability. When the snowband approached the high terrain during the enhancement stage, the various instabilities were triggered by the low-level frontogenesis, terrain circulation, and strong wind shear associated with the low-level jet. Further, a modified Q-vector divergence including generalized potential temperature was calculated to diagnose the vertical motion. It showed that the frontogenesis terms contributed greatly to the negative Q-vector divergence along the moist isentropes, while the pseudo-vorticity terms played a role in the regions with strong wind shear associated with the low-level jet in the warm section, suggesting both were important in stimulating the ascending motion. The regions with negative Q-vector divergence had a close relationship with the vertical structure of convection, indicating the potential to track the development of the snowband in the next few hours.摘要2017年1月26日, 中国东北地区发生了一次短时强降雪过程.本文利用ECMWF再分析数据诊断该过程的可能触发机制.分析表明, 该过程可分两个阶段:初生阶段降雪远离高地形, 低层锋生和有利的辐散场配置激发上升运动释放不稳定;增强阶段雪带接近长白山, 低层锋生,地形环流以及与低空急流有关的风切变共同释放锋前不稳定.本文进一步计算了包含广义位温的修正Q矢量方程.结果表明, 锋生项对沿湿等熵线的负Q矢量散度贡献较大, 而拟涡度项在暖区强风切变区域中比较显著, 两项在激发上升运动中同等重要.  相似文献   

Comparative research on visibility and light extinction of PM2.5 components during 2014–17 in the North China plain: 2014-2017年华北平原PM2.5组分消光与能见度对比研究          下载免费PDF全文

《大气和海洋科学快报》2021,14(2):100034

Severe air pollution with visibility deterioration has long been a focus in the North China Plain (NCP). In this study, concentration and light extinction analysis of PM_2.5 chemical components were carried out from 2014 to 2017 to study the pollution characteristics in Baoding, a case city of the NCP. The annual average concentration of total PM_2.5 components showed a declining trend, decreasing by 11 µg m⁻³ (water-soluble inorganic ions), 23 µg m⁻³ (carbonaceous aerosols), and 1796 ng m⁻³ (inorganic elements). Contributing 82.9% to the concentration of total ions, the dominant components, NH₄⁺, NO₃⁻, and SO₄²⁻ became the main pollutants in PM_2.5 pollution. Based on the IMPROVE algorithm, the average reconstructed PM_2.5 mass concentration was 93 ± 69 µg m⁻³ during the observation period. Meanwhile, the light extinction coefficients were 373.8 ± 233.6 M m⁻¹, 405.3 ± 300.1 M m⁻¹, 554.3 ± 378.2 M m⁻¹ and 1005.2 ± 750.3 M m⁻¹, in spring, summer, autumn, and winter, respectively. Ammonium sulfate, ammonium nitrate, and organic matter were the largest contributors to light extinction, accounting for a total of 55%–77% in the four seasons. The b_sca (light scattering by particles and gases) reconstructed from PM_2.5 components (Rb_sca) and the b_sca converted from visibility (Vb_sca) were compared to evaluate the performance of the IMPROVE algorithm, revealing a high correlation coefficient of 0.84. The high values of Vb_sca were underestimated while the low values were overestimated, as determined through comparison with the one-to-ne line. Especially, when Rb_sca > 1123 M m⁻¹ (corresponding to < 2.0 km, approximately), Vb_sca was underestimated by 17.6%. PM_2.5 mass concentration and relative humidity also had an impact on the estimation.摘要华北平原大气污染与低能见度状况一直是人们关切的问题.本文通过分析2014 - 2017年PM_2.5化学成分的浓度和消光效果, 研究了华北平原典型城市保定市的大气污染特征.结果表明, PM_2.5组分的年均浓度显示下降趋势, 水溶性无机离子,碳质气溶胶和金属元素分别减少了11 µg m⁻³, 23 µg m⁻³和1796 ng m⁻³.NH₄⁺,NO₃⁻和SO₄²⁻是PM_2.5污染的主要污染物, 三者之和占总离子浓度的82.9%.基于IMPROVE方程对细颗粒物进行重构, 在观测期间PM_2.5质量浓度平均为93 ± 69 µg m^−3, 春季,夏季,秋季和冬季的消光系数分别为373.8 ± 233.6 M m⁻¹,405.3 ± 300.1 M m⁻¹,554.3 ± 378.2 M m⁻¹和1005.2 ± 750.3 M m⁻¹.硫酸铵,硝酸铵和有机物对消光的贡献最大, 不同季节下占比达55% ~77%.通过PM_2.5组分进行重构, 利用IMPROVE算法计算得到Rbsca, 用能见度测量值转换得到Vbsca, 二者具有较高的相关性 (r²=0.84) ;但存在Vbsca的高值被低估, Vbsca的低值被高估的现象;特别是当Rbsca > 1123 M m⁻¹ (对应能见度约小于2.0 km) 时, Vbsca的值被低估了17.6%.高浓度PM_2.5和高湿度对IMPROVE算法结果有显著的影响.  相似文献   

Possible contribution of the PDO to the eastward retreat of the western pacific subtropical high: PDO对西太平洋副热带高压年代际东退的可能贡献          下载免费PDF全文

《大气和海洋科学快报》2021,14(1):100005

Previous studies have demonstrated that the western Pacific subtropical high (WPSH) has experienced an eastward retreat since the late 1970s. In this study, the authors propose that this eastward retreat of the WPSH can be partly attributed to atmospheric responses to the positive phase of the Pacific decadal oscillation (PDO), based on idealized SST forcing experiments using the Community Atmosphere Model, version 4. Associated with the positive phase of the PDO, convective heating from the Indian Peninsula to the western Pacific and over the eastern tropical Pacific has increased, which has subsequently forced a Gill-type response to modulate the WPSH. The resulting cyclonic gyre over the Asian continent and the western Pacific in the lower troposphere is favorable for the eastward retreat of the WPSH. Additionally, the resulting anticyclonic gyre in the upper troposphere is favorable for the strengthening and southward expansion of the East Asian westerly jet, which can modulate the jet-related secondary meridional–vertical circulation over the western Pacific and promote the eastward retreat of the WPSH.摘要以往的研究已证实, 西太平洋副热带高压 (副高) 在1970s后期减弱东退.基于大气模式 (CAM4) 的理想型海温强迫试验, 结果表明:副高的东退可能是大气对于正位相太平洋年代际振荡 (PDO) 的相应.伴随着PDO转变为正位相, 西太平洋至印度半岛以及热带东太平洋的对流加热增强, 大气表现为Gill型响应, 在亚洲大陆至西太平洋上空低层产生气旋性异常, 有利于副高东退.同时, 高层产生反气旋异常, 使得东亚西风急流加强和向南扩展, 进而调节西太平洋上空的次级环流, 进一步有利于副高东退.  相似文献