热带印度洋MJO活动异常对四川盆地降水的影响

利用四川省132个气象观测站降水资料和NOAA的逐日向外长波辐射(OLR)资料,分析了主汛期热带东印度洋MJO活动异常年低频对流传播的显著差异,及其影响四川盆地主汛期降水的物理过程。探讨了热带东印度洋MJO活跃年低频振荡向四川盆地传播的路径和源头,以及孟加拉湾西南季风系统、东亚副热带季风系统的低频振荡分别对四川盆地主汛期低频对流活动的影响。结果表明:热带印度洋的低频对流激发了孟加拉湾西南季风ISO进入活跃期,并在西南气流的引导下继续向四川盆地传播;低频对流先从热带印度洋东传至菲律宾群岛南部的热带洋面,并向东亚副热带地区北传,激发了东亚副热带季风ISO的活跃加强,进而向四川盆地西传。热带印度洋MJO活动异常对四川盆地降水的调制,正是通过两支季风系统(孟加拉湾夏季风和东亚副热带夏季风)的共同作用,影响了四川盆地主汛期异常的对流活动以及降水的多寡。      

热带印度洋MJO对4—6月长江中下游地区降水的影响

利用站点降水资料、美国气候预测中心(CPC)的MJO指数和NCEP/DOE AMIP-II再分析资料,研究了热带印度洋MJO对4—6月长江中下游地区降水的影响及可能机制。(1) 热带印度洋MJO对长江中下游地区降水有显著影响:热带印度洋MJO偏强(偏弱)时,同期以及滞后1～2候时该地区降水偏多(偏少)。(2) 热带印度洋MJO处在不同位相时,大尺度背景场有明显的差别:热带印度洋MJO偏强(偏弱)时,同期以及滞后1～2候时MJO活跃对流中心位于热带印度洋(西太平洋),西太平洋副热带地区表现为反气旋性(气旋性)环流异常,孟加拉湾为气旋性(反气旋性)环流异常,长江中下游地区出现了异常上升(下沉)运动,水汽辐合增强(减弱);伴随MJO的东传,水汽输送异常来源有所变化。(3) 热带印度洋MJO通过激发Gill型响应和Rossby波列,对长江中下游地区降水产生影响。      

热带季节内振荡对2008年初南方持续性冰冻雨雪天气的影响

利用滤波、EOF和合成分析等统计方法及NCEP和NOAA提供的资料,分析了与2008年初我国南方罕见持续性冰冻雨雪天气有关的水汽输送演变情况,发现持续性与热带大气季节内振荡（MJO）和中低纬地区高低层环流的30 ~ 60天低频振荡关系体现为：当MJO活动以印度洋中东部赤道地区对流加强、印度尼西亚对流受抑制为特征时,印度地区700 hPa出现低频气旋有利于70 ~ 80 ?E的槽加深。与此同时,我国台湾以东洋面出现低频反气旋,有利于西太平洋副高加强。低压槽和副热带高压（副高）之间的偏南风导致孟加拉湾和南海的水汽同时向我国南方地区输送。与低层系统相配,200 hPa低频反气旋位于南压大陆,在该低频反气旋东北侧则为低频气旋,二者之间的低频西北风与低层的低频南风构成了反Hadley型局地经向环流,并导致高层西风急流入口区反气旋侧的高层辐散区向南偏移,使低频经向环流的上升支控制我国南方地区,该上升气流将来自孟加拉湾和南海的水汽抬升至高层,十分有利2008年初我国罕见冻雨的降水异常。通过对比分析相同时段降水异常偏少的1993年中低纬高低层低频环流场,发现1993年的低频环流分布形势与2008年的相反,说明了季节内振荡确实是造成2008年初我国南方地区持续性降水的重要因素之一。     

热带印度洋MJO活动对孟加拉湾西南夏季风季节内振荡的影响

通过对1979—2008年热带太平洋30—60 d振荡(Madden-Julian Oscillation,MJO)指数、美国国家环境预报中心再分析资料和日本气象厅降水资料的分析,发现热带东印度洋MJO强度和传播状况影响孟加拉湾西南夏季风季节内振荡及相关低频环流、对流和降水分布。当热带东印度洋MJO在春末夏初较活跃时,孟加拉湾西南季风季节内振荡活动在4—8月比其不活跃时提前约20 d(约1/2个周期),其对于孟加拉湾西南季风季节内振荡的影响可持续整个季风期,使西南季风的季节内振荡不仅酝酿期和活跃期提前发生,季风期有所延长,季节内振荡也更强。西南季风季节内振荡具有明显的北传和东传特征,北传沿孟加拉湾通道从赤道向副热带推进,而东传则沿10°—20°N从孟加拉湾向东传至南海地区。春末夏初时热带东印度洋MJO的异常状况,正是通过对西南季风季节内振荡东传和北传的影响,进而对孟加拉湾西南季风季节内振荡在季风期的酝酿、维持和活跃产生作用,这种作用同时体现在强度和时间上。孟加拉湾西南夏季风季节内振荡强度与热带东印度洋MJO在4月21日—5月5日的活动呈现显著负相关,当热带东印度洋MJO在春末夏初较活跃时,孟加拉湾西南夏季风季节内振荡的强度较大,在5—8月经历3次季节内振荡波动,低频对流场和环流场在1—3位相(孟加拉湾西南夏季风季节内振荡为正位相)和4—6位相(负位相)时呈反位相特征,这是由MJO低频对流的东传及在孟加拉湾和南海这两个通道上的北传引起的。从印度半岛到菲律宾群岛的降水在1—3位相和4—6位相上分别为正异常和负异常,其中,在第2位相(孟加拉湾西南季风季节内振荡波峰)和第5位相(孟加拉湾西南季风季节内振荡波谷)时分别为降水最大正异常和最大负异常。反之,在热带印度洋MJO在春末夏初不活跃年时,孟加拉湾西南夏季风季节内振荡活动较弱,强度偏弱且振荡也不规律。     

影响海南岛的热带气旋与MJO的关系

利用澳大利亚气象局MJO(Madden-Julian Oscillation)指数(1979—2015年)资料、NCEP/NCAR全球再分析格点资料和中国气象局上海台风研究所台风资料,分析了MJO不同位相、强度与7—10月影响海南岛的热带气旋活动的关系。结果表明:7—10月影响海南岛的热带气旋活跃期和沉寂期与MJO的位相和强度有关,但7—8月和9—10月的热带气旋活跃期和沉寂期对应的MJO位相和强度有所不同。在7、8月,当MJO处于强的第3、6位相或弱的第4位相时有利于热带气旋影响海南岛,当MJO处于强的第1、2、8位相时则不利于热带气旋影响海南岛。在9、10月,当MJO处于7位相时有利于热带气旋影响海南岛,当MJO处于1位相时则不利于热带气旋影响海南岛。无论是7、8月还是9、10月,有利于热带气旋偏多和偏少的MJO位相对应的环流形势基本相反。     

2008年初中国南方低温雨雪冰冻天气的季节内振荡特征

利用中国气象局国家气象中心750站逐日平均气温和降水资料、NCEP/NCAR再分析的逐日风场和近地面气温资料、以及NOAA逐日向外长波辐射资料,分析了2008年1月我国南方发生的低温冰冻雨雪天气异常.结果表明,这次冰雪灾害伴有异常的季节内振荡特征,整个过程共包括4次降温、降水过程,这4次降温过程都在近地面气温30～60...     

热带MJO和ENSO对西北太平洋热带气旋影响研究综述

对西北太平洋热带气旋的活动规律作了综合评述,简单回顾了热带季节内振荡（MJO）特征和厄尔尼诺/南方涛动（ENSO）特征以及两者间关系,较系统地总结了近年来国内外学者关于MJO和ENSO对西北太平洋海域热带气旋活动影响和机理等方面的研究成果。讨论的热带气旋活动特征包括源地、频数、路径、强度、生命期和登陆等几个方面,并简单讨论了目前该领域存在的科学问题和未来可能的研究方向。     

一次大范围雨雪天气过程的雷达回波特征分析

针对2015年1月9日贵州中西部出现的大范围雨雪天气过程,结合探空观测资料,利用新一代天气雷达基本产品分析了此次雨雪天气过程的雷达回波强度、回波高度、垂直结构和径向速度等基本变化特征。分析结果表明:雨雪天气过程雷达回波的基本特征为,无明显强回波中心,回波结构呈丝缕状,边缘模糊,降水粒子回波高度较低。从径向速度图分析来看,近地层为均匀的东北风,“牛眼”型结构,低空急流;中高层为北部为冷平流,南部为暖平流,与过程降水分布情况基本一致。深厚的冷湿结构、静止锋区的逆温层结构以及高空的西南风急流给这次大范围雨雪天气过程的形成和维持造成有利的条件。      

热带气旋影响广西造成大范围暴雨的天气类型及预报

利用EC数值预报资料,对影响广西热带气旋进行了分析,归纳整理出影响大范围暴雨的天气类型,并寻找其相关的气象要素和预报因子,通过建立各型的预报规则并进行预报应用,效果较为理想,为防台工作有一定的参考价值。     

热带气旋影响广西造成大范围暴雨的天气类型及预报

利用EC数值预报资料,对影响广西热带气旋进行了分析,归纳整理出影响大范围暴雨的天气类型,并寻找其相关的气象要素和预报因子,通过建立各型的预报规则并进行预报应用,效果较为理想,为防台工作有一定的参考价值。     

POSSIBLE IMPACTS OF MADDEN-JULIAN OSCILLATION ON THE SEVERE RAIN-SNOW WEATHER IN CHINA DURING NOVEMBER 2009

Possible relationships between MJO and the severe rain-snow weather in Eastern China during November of 2009 are analyzed and results show that a strong MJO process is one of the strong impact factors.MJO is very active over the Indian Ocean in November 2009.Especially,it maintains 9 days in MJO phase 3,just corresponding to the two strongest rain-snow processes.Composites of MJO events show that when the MJO convective center is located over the Indian Ocean,the probability of rainfall is significantly increased and the temperature is lower than normal in eastern China,which is consistent with the situation in November of 2009.Atmospheric circulation anomalies of mid-and higher-latitudes can be influenced by the tropical MJO convection forcing and this influence could be realized by teleconnection.When the MJO is over the Indian Ocean,it is favorable for the maintenance of a circulation pattern of two ridges versus one trough at mid-and higher-latitudes.Meanwhile,the western Pacific subtropical high is stronger and more westward than normal,and a significant convective belt appears over eastern East Asia.All these circulation anomalies shown in the composite result also appeared in the observations in November 2009,which indicates the general features of relationships between the MJO and the circulation anomalies over the extratropics.Besides the zonal circulation anomalies,the MJO convection can also lead to meridional circulation anomalies.When the MJO convection is located over the Indian Ocean,the western Pacific is dominated by anomalous descending motion,and the eastern East Asia is controlled by strong convergence and ascending motion.Therefore,an anomalous meridional circulation is formed between the tropics and middle latitudes,enhancing the northward transportation of low-level moisture.It is potentially helpful to understanding and even forecasting such kind of rain-snow weather anomalies as that in November 2009 using MJO.     

积云参数化和分辨率对MJO数值模拟的影响

用中国科学院大气物理研究所发展的一个大气环流模式,使用不同的积云参数化方案和分辨率进行了6个模拟试验,考察了积云参数化方案和模式分辨率对热带大气季节内振荡（MJO）模拟的影响。结果显示：积云参数化方案和分辨率都会影响MJO的模拟。但积云参数化方案决定了模式对MJO模拟的基本能力,决定了模拟的MJO的基本特征。分辨率的变化并不能使模拟的MJO发生本质的改变,分辨率的作用更多的是对MJO的模拟起一定的调制作用,而这种调制作用又受到积云参数化方案的制约。在改进积云参数化方案的基础上提高模式的分辨率会在某些方面改善MJO的模拟。但是分辨率的提高需要同时提高水平分辨率和垂直分辨率,单独提高水平分辨率会降低模式模拟MJO的能力,引入更多的小尺度的高频扰动。非绝热加热垂直廓线对模式模拟MJO有重要的影响,而非绝热加热廓线很大程度上取决于所使用的积云参数化方案。模式水平分辨率的变化不会对加热廓线的结构产生明显的影响,而垂直分辨率的变化会对加热廓线的垂直结构产生一定的调制作用,进而对模拟的MJO起到调制作用。     

气候变暖对中国水稻生产可能影响的研究

利用随机天气模型,将大气环流模式预测的气候情景与水稻模式相链接,研究了气候变暖对中国水稻生产的可能影响。结果表明,大气中ＣＯ２浓度加倍,中国水稻主产区适宜水稻生长的日数将延长６～１１ｄ,积温增加２２０～３３０℃·ｄ。积温的相对增长率由南向北呈增长趋势。水稻产量形成期低温天气出现频率将减少,而高温天气出现的频率增加。若品种与播种、移栽期不变,水稻产量将下降;而若通过改变品种使作物生育期基本保持目前的状况,减产幅度将比品种不变时明显偏小,部分地区还有可能增产。     

IMPACTS OF CUMULUS PARAMETERIZATION AND RESOLUTION ON THE MJO SIMULATION

Madden-Julian Oscillations (MJO) in six integrations using an AGCM with different cumulus parameterization schemes and resolutions are examined to investigate their impacts on the MJO simulation. Results suggest that the MJO simulation can be affected by both resolution and cumulus parameterization, though the latter, which determines the fundamental ability of the AGCM in simulating the MJO and the characteristics of the simulated MJO, is more crucial than the former. Model resolution can substantially affect the simulated MJO in certain aspects. Increasing resolution cannot improve the simulated MJO substantially, but can significantly modulate the detailed character of the simulated MJO; meanwhile, the impacts of resolution are dependent on the cumulus parameterization, determining the basic features of the MJO. Changes in the resolution do not alter the nature of the simulated MJO but rather regulate the simulation itself, which is constrained by cumulus parameterization schemes. Therefore, the vertical resolution needs to be increased simultaneously. The vertical profile of diabatic heating may be a crucial factor that is responsible for these different modeling results. To a large extent, it is determined by the cumulus parameterization scheme used.     

POSSIBLE INFLUENCES OF THE TROPICAL INDIAN OCEAN DIPOLE ON THE EASTWARD PROPAGATION OF MJO

Based on multiple datasets, correlation and composite analyses, and case studies, this paper investigated possible influences of the Indian Ocean dipole （IOD） mode on the eastward propagation of intraseasonal oscillation in the tropical atmosphere. The results showed that （1） the 30-60 day outgoing longwave radiation anomalies in the southeastern Indian Ocean and the 30-60 day 850-hPa zonal wind anomalies over the equatorial central Indian Ocean were significantly correlated with the IOD index; （2） during positive IOD years, the anomalously cold water in the southeastern Indian Ocean and the 850-hPa anomalous easterlies over the equatorial central Indian Ocean might act as barriers to the continuously eastward propagation of the intraseasonal convection, which interrupts the Madden-Julian oscillation （MJO） propagation in the eastern equatorial Indian Ocean and western Pacific; and （3） during negative IOD years, the anomalously warm water in the southeastern Indian Ocean and the low-level westerly anomalies over the equatorial central Indian Ocean favor the eastward movement of MJO.     

MJO与ENSO关系的研究进展

MJO是热带大气的强信号,ENSO是热带太平洋海气相互作用的最强信号,两者的时间空间尺度不同,但都对全球范围的大气活动有显著的影响,且两者之间也有着密切的关系。总结了近年来MJO和ENSO相互关系方面的研究,并在此基础上提出需要进一步研究的问题。     

THE IMPACTS OF MADDEN-JULIAN OSCILLATION ON SPRING RAINFALL IN EAST CHINA

Phase composite analyses are conducted to investigate the possible effect of the Madden–Julian oscillation(MJO)on the spring rainfall anomalies in East China by using the Real-time Multivariate MJO(RMM)index from Australian Meteorological Bureau.The results show that the rainfall anomalies over the mid-and lower-valley of Yangtze River are positive when the MJO shifts eastward to the mid-and eastern-Indian Ocean,and anomalous precipitation over South China are positive when the MJO moves further eastward to the maritime continent,whereas spring rainfall anomalies over East China are negative in the other MJO episodes.The MJO impacts on the precipitation over East China result from the changes in large-scale atmospheric circulation as well as vorticity and water vapor transportation in the mid-and lower-troposphere.     

MJO对我国东部春季降水影响的分析

利用澳大利亚气象局的MJO(Madden-Julian Oscillation)指数,通过位相合成及对比分析研究了MJO对我国东部春季降水的影响.研究表明,当MJO传播至中东印度洋时,我国长江中下游地区的春季降水为正异常,当其进一步东传至中南半岛-印尼群岛一带时,我国华南地区的春季降水为正异常,而在其他活动阶段不利于我国东部的春季降水.对比分析表明,MJO的活动主要通过引起大尺度环流异常、对流层中低层涡度及水汽输送的异常,进而对我国东部春季降水产生明显的影响.     

NUMERICAL SIMULATION ON THE RESPONSE OF LAND SURFACE TO SEVERE WEATHER

A coupled model of RAMS3b(Regional Atmospheric Modeling System,Version 3b)andLSPM(a land surface process model),in which some basic hydrological processes such asprecipitation,evapotranspiration.surface runoff,infiltration and bottom drainage are included,has been established.With the coupled model,we have simulated the response of soil to the severeweather process which caused the disastrous flood in north italy during 4-7.November,1994,simultaneously compared with the observation and the original RAMS3b,which has a soil andvegetation parameterization scheme(hereafter,SVP)emphasizing on the surface energy fluxes,while some hydrological processes in the soil are not described clearly.The results show that the differences between coupling LSPM and SVP exist mainly in theresponse of soil to the precipitation.The soil in the SVP never saturates under the strong input ofprecipitation,while the newly coupled model seems better,the soil has been saturated for one dayor more and causes strong surface runoff,which constitutes the flood.Further sensitivityexperiments show that the surface hydrological processes are very sensitive to the initial soilmoisture and soil type when we compared the results with a relatively dry case and sandy soil.The coupled model has potentiality for simulation on the interaction between regional climateand land surface hydrological processes,and the regional water resources research concerningdesertification,drought and flood.     

GPS水汽资料在江西强对流天气预报中的初步应用

利用GPS/MET 水汽监测资料,对2009-2011 年江西省8 次具有代表性的强天气过程的GPS 可降水量变化进行分析和研究,并重点对2011 年6 月10-15 日的降水过程进行分析.结果表明,在每次强天气的发展过程中,水汽含量其增长率均表现为不均匀,但均呈现剧烈增长;6 次强天气过程的初始GPS 可降水量高于6...