亚洲夏季风水汽输送的年际年代际变化与中国旱涝的关系

利用1958～2002年的NCEP-R1和ERA-40逐日再分析资料以及中国160站点月平均降水资料探讨了亚洲夏季风水汽输送的年际年代际变化及其与中国降水异常的关系. 分析结果表明,亚洲夏季风水汽输送和中国夏季降水的异常主模态呈现显著的准两年变化周期. 当南亚夏季风纬向水汽输送偏强（弱）时,东亚—西北太平洋地区水汽输送的偶极型异常有利于长江中下游地区和江淮流域的水汽辐合负（正）异常与华南和华北地区的水汽辐合正（负）异常,从而引起中国东部的经向三极子雨型,即长江中下游地区和江淮流域的偏旱（涝）与华南和华北地区的偏涝（旱）. 1970s年代末之后,亚洲夏季风水汽输送的年代际减弱与西北太平洋地区水汽输送的偶极型异常相配合,导致长江中下游地区的持续偏涝与华南和华北地区的持续偏旱. 从中国夏季降水异常与水汽通量辐合异常的同相对应关系来看,ERA-40资料对亚洲夏季风水汽输送年际年代际变化的描述能力强于NCEP-R1资料.     

北极海冰与夏季欧亚遥相关型年际变化的联系及对我国夏季降水的影响

本文利用NCEP/NCAR等再分析资料和CAM3.1数值模式研究了夏季欧亚中高纬遥相关型年际变率与前期春季北极海冰变化的联系及其对我国夏季降水影响的可能机制.结果表明,夏季北大西洋-欧亚中高纬地区500 hPa位势高度场自然正交分解第二模态表现为"-+-+"遥相关波列,其中格陵兰岛-北大西洋和乌拉尔山地区为异常高空槽区所控制,而欧洲和贝加尔湖附近地区则为异常高压脊区,这种波列分布与欧亚中高纬EU型遥相关型十分类似.当遥相关波列为"-+-+"（"+-+-"）型分布时,前期春季巴伦支海北部和巴芬湾一带海冰偏少（多）,同期夏季巴伦支海北部一带海冰亦持续偏少（多）,同时在我国东北北部地区、长江和黄河之间地区降水明显偏少（多）.深入分析发现,巴伦支海北部和巴芬湾一带海冰偏少后,由于该地区湍流热通量明显偏强,在动力过程影响方面会形成异常Rossby波源,准定常Rossby波活动通量将向东亚地区传播,使得夏季欧亚中高纬"-+-+"遥相关波列出现.另外,海冰异常偏少后,在热动力过程影响方面,4-5月欧亚中高纬乌拉尔山-贝加尔湖以北地区积雪会出现"西少东多"偶极子型异常分布,其通过影响后期土壤湿度及下垫面热通量异常,也有利于夏季欧亚中高纬遥相关波列的维持.伴随着欧亚中高纬"-+-+"遥相关波列的出现,乌山阻塞高压偏弱,东亚槽偏浅,且亚洲副热带急流随之加强,贝加尔湖以北的副极地地区出现西风异常,东亚副热带急流北侧出现东风异常,贝加尔湖以南地区为异常反气旋控制,南下冷空气活动减弱.受到上述环流形势影响,我国东北北部地区、黄河和长江之间地区降水明显偏少.当巴伦支海北部和巴芬湾区域海冰偏多时,结论则反之.最后,基于春季海冰指数和晚春偶极子型积雪指数,我们建立了江淮流域夏季降水的预测模型,回报结果表明其对江淮流域夏季降水的年际变率具有较高的预测技巧.     

中尺度模式积云参数化方案的改进及其在暴雨模拟中的应用

本文针对中国暴雨发生发展天气特征,改进和发展了一种适合于描述东亚暴雨的中尺度积云参数化方案.首先基于近年来(1990—2010)江淮流域汛期降水合成分析的基础上,诊断出组织化对流降水环境的动力参数;其次利用该动力参数作为动力控制条件,改进了Kain-Fritsch Eta中尺度积云对流参数化方案;最后利用改进的中尺度积云参数化方案对梅雨期暴雨、华南前汛期暴雨过程进行了数值模拟,结果表明:改进后的中尺度积云参数化方案对上述两次暴雨过程的落区及强度的模拟,均有明显改进.     

变网格大气模式对1998年东亚夏季风异常的模拟研究

本文利用法国国家科研中心(CNRS)动力气象实验室(LMD)发展的可变网格的格点大气环流模式LMDZ4,对1998年东亚夏季降水进行了模拟,考查了变网格模式对东亚夏季降水的模拟性能.结果表明,模式在一定程度上能模拟出东亚夏季降水的极大值中心、夏季风雨带以及降水由东南向西北递减的空间分布特征.模式基本再现了1998年夏季两次雨带的进退特征,包括降水强度、雨带范围等,从而合理再现了1998年夏季江淮地区的"二度梅"现象.与观测相比,模拟的不足在于:在陡峭地形区附近存在虚假降水;江淮和华北地区以及四川盆地存在水汽输送的气旋式辐合偏差,同时高层环流辐散偏强,使得下层暖湿空气辐合上升、降水偏多;在东南地区存在反气旋式的水汽输送偏差,30°N以南地区降水偏少.对于1998年的"二度梅"现象,模拟偏差主要表现为长江中下游地区两次(特别是第二次)较强降水持续时间偏短,强降水范围偏小,而黄淮和华南地区却降水偏多.分析表明,模式对两次梅雨期降水的模拟偏差直接受环流形势模拟偏差的影响.LMDZ4区域模式版本的特点一是区域加密,二是加密区内预报场每10天向再分析资料恢复一次.敏感试验结果表明,LMDZ4加密区向强迫场的10天尺度恢复总体上有利于提高模式对华北降水的模拟能力,而对长江流域和华南降水的模拟具有不利影响.较之均匀网格模拟试验,加密试验由于在东亚的分辨率大大提高,对东亚夏季降水模拟效果更好.     

西北太平洋热带气旋活动影响区域大尺度环流的数值模拟研究

本文利用"模式手术"方法研究了西北太平洋热带气旋(TC)对东亚—西北太平洋区域大尺度环流的影响.结果表明,夏季频繁的西北太平洋TC活动导致东亚夏季风增强,季风槽加深;西太平洋副热带高压东退,位置偏北;东亚副热带高空急流强度增强,北太平洋(东亚大陆)上急流轴偏北(偏南);热带地区(副热带地区)的对流层中低层出现异常上升气流(下沉气流),并且从低纬向高纬呈现异常上升气流和异常下沉气流交替分布特征.在中国东南沿海,TC降水导致夏季降水量明显增加;而在长江中下游和华北地区,TC活动引起的异常下沉气流使夏季降水量显著减少.因此,夏季西北太平洋TC活动对东亚—西北太平洋区域气候有显著影响.     

Moisture budget variations in the Yangtze River Basin, China, and possible associations with large-scale circulation

We analyzed seasonal and annual variations of the whole layer atmospheric moisture budget and precipitation during 1961–2005 and their associations with large-scale circulation in the Yangtze River basin, China. The results indicated increasing moisture budget in summer and winter, but decreasing moisture budget in spring and autumn. Positive correlations between moisture budget and precipitation illustrate tremendous impacts the moisture budget has on the precipitation changes across the Yangtze River basin. In terms of seasonal variations, significant correlations were observed between precipitation and moisture budget in spring and autumn in the upper Yangtze River basin. Besides, we also analyzed changes of geopotential height. The positive trends of the geopotential height (850 hPa) were observed in the East Asia and the negative trends in the middle and west Pacific Ocean, indicating increasing geopotential height from south to north in east Asia which largely limited the moisture propagation to north China. While decreasing meridional geopotential height from west to east along the Yangtze River basin caused more moisture propagation from the west to the east parts of the study region, which may benefit more precipitation in the middle and lower Yangtze River basin.     

Heating status of the Tibetan Plateau from April to June and rainfall and atmospheric circulation anomaly over East Asia in midsummer

Based on the 1958-1999 monthly averaged reanalysis data of the National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) and the rainfall data of 160 Chinese surface stations, the relationship between rainfall and the atmospheric circulation anomaly over East Asia (EA) in July and the sensible heating (SH) over the Tibetan Plateau (TP) from April to June (AMJ) is investigated by using the rotational experimental orthogonal function (REOF) method. The results show that the TP is an isolated heating source in this period. The lagged correlation analysis between the first rotational principal component (RPC) of SH over the TP in May and rainfall of EA in July demonstrates that strong SH over the TP before July leads to a positive rainfall anomaly over the TP, the valley between the Yangtze River and Huaihe River, and the regions south and southeast of the TP, and the Sichuan Basin and Yunnan-Guizhou Plateau, but less rainfall anomaly over the regions north, northeas     

A comparative study of the atmospheric circulations associated with rainy-season floods between the Yangtze and Huaihe River Basins

Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins for the 21 years(1990–2010),using the daily rain gauge measurements taken in the 756 stations throughout China and the NCEP/reanalysis data for the rainyseasons(June–July)from 1990 to 2010.The major differences in the atmospheric circulations and physical quantity fields between the Yangtze and Huaihe River basins are as follows:for flooding years of the Yangtze River Basin,the South Asia high center is located further east than normal,the blocking high over the Urals and the Sea of Okhotsk maintains,and the Meiyu front is situated near 30°N whereas for flooding years of the Huaihe River Basin,the South Asia high center is further west than normal,the atmospheric circulations over the mid and high latitudes in the Northern Hemisphere are of meridional distribution,and the Meiyu front is situated near 33°N.In addition,there are distinct differences in water vapor sources and associated transports between the Yangtze and Huaihe River basins.The water vapor is transported by southwesterly flows from the Bay of Bengal and monsoon flows over the South China Sea for flooding years of the Yangtze River Basin whereas by southeast monsoons from the eastern and southern seas off China and monsoon flows over the South China Sea for flooding years of the Huaihe River Basin.     

梅雨与北极涛动及平流层环流异常的关联

平流层过程如何影响气候变化是一个大家关注的科学问题,在WCRP中专门设置了一个研究子计划SPARC.本文的分析研究表明,中国的梅雨异常可能受到平流层大气环流异常的影响,而这种影响是通过北极涛动（AO）的变化来实现的.从分析和计算结果可以看到,二月份北半球30 hPa位势高度的EOF第一主分量对应着副热带和高纬度地区的显著下传异常波作用量,其第三主分量对应着极地地区的显著下传异常波作用量,这些下传的异常波作用量都对三月份AO形势的形成有明显的贡献.三月份的AO则会通过影响东亚地区夏季对流层大气的冷暖状况和环流,在长江中下游地区导致异常垂直运动和辐散辐合形势,从而影响夏季的梅雨降水.     

长江上游地区可利用降水量的气候特征

利用长江上游地区107个观测站1960-2008年气温、降水观测资料,采用陆面蒸发经验模型计算得到各观测站的月蒸发量,再根据水量平衡关系,得到可利用降水量,采用数理统计、REOF分析和M-K突变检验等方法,分析长江上游地区可利用降水量的气候变化特征.结果表明:长江上游可利用降水量季节变化显著,5-9月长江上游可利用降水...     

近50a淮河流域汛期降水日数和强度的分布与变化特征

选用1961-2010年淮河流域145个地面气象站的观测资料,分析淮河流域汛期(5-9月)降水的时空变化规律.结果表明:淮河流域汛期降水的空间分布不仅受到地理位置和地形的影响,而且与湿度和风速的空间分布具有较好的相关性;在时间变化上,雨日出现频率有下降的趋势,但暴雨日比重和暴雨日平均降水量均有升高的趋势.淮河流域汛期暴雨日出现频率以及各类型雨日的平均降水量均有上升的趋势,强降水时空变化呈现局地性和频发性.     

El Nino演变不同阶段东亚大气环流年际异常型的数值模拟

给定1948～1999年逐月变化的全球观测的海表温度分布，使用全球大气环流模式（CCM3/NCAR）模拟了大气对海表温度变化的响应，利用SVD和合成检验方法，分析了El Nino发展阶段夏季、成熟阶段冬季以及衰亡阶段夏季东亚大气环流的年际异常型.结果表明：El Nino发展阶段夏季，中国东北、朝鲜半岛以及日本海附近为高度负异常中心，西太平洋副高偏弱、偏东，东亚夏季风增强；El Nino成熟阶段冬季，东亚大槽加强，东亚北部冬季风加强；El Nino衰亡阶段夏季，西太平洋副高偏强、偏南、西伸，东亚夏季风减弱；El Nino事件在其衰亡阶段夏季与东亚大气环流异常的关系最紧密，其次是成熟阶段冬季，最后是发展阶段夏季.模拟的El Nino演变不同阶段东亚大气环流年际异常型易于解释以往研究中观测分析揭示的由El Nino造成的我国东部气温和降水异常型.     

Regional difference of annual precipitation and discharge variation over west China during the last 50 years

Using annual precipitation and discharge data measured in the past five decades,this paper analyzed the regional differences over west China in terms of climate and discharge variations,and investigated the relationship between the regional characteristics and the activities of South and East Asian sum-mer monsoon. Results revealed that the precipitation and discharge in the upper reaches of the Yellow River (Central West China) have a negative correlation with those in Xinjiang (northwest China) and the Yarlung Zangbo River (the upper reaches of the Brahmaputra Rive,southwest China) regions. The geographical patterns of precipitation and discharge variations are different over west China,i.e. the regional climate displays the alteration of dry-wet-dry or wet-dry-wet from north to south in west China. The negative correlation of annual discharges between Xinjiang and the upper reaches of the Yellow River is found statistically significant in the decadal scale,and that between the Yarlung Zangbo River and the upper reaches of the Yellow River is found active in the interannual scale. The regional char-acteristics indicate that the discharge/precipitation variations in the upper reaches of the Yellow River are dominated by the East Asian summer monsoon while their variations in Xinjiang are affected by both the west wind and East Asian summer monsoon.     

索马里急流的年际变化及其对半球间水汽输送和东亚夏季降水的影响

利用美国国家环境预报中心和美国国家大气科学研究中 心（NCEP/NCAR）再分析月平均气候资料以及Xie和Arkin分析的月平均降水资料（1968～199 8年），针对索马里低空急流（SMJ）的年际变化及其对东亚夏季降水的影响问题展开了分析 研究. 结果揭示，SMJ作为最主要的越赤道气流，对两个半球间水汽输送起最关键的作用， 它把水汽从冬半球输送到夏半球. 夏季SMJ的年际变化有全球范围内的环流异常与之相联系 ，特别是东亚沿岸的波列状异常分布、南亚高压以及澳大利亚以南的偶极型异常分布；它 也同春季的北印度洋等海区的海温异常有密切关系. 研究还表明，春季SMJ的年际变化对东 亚夏季降水和大气环流有显著影响，由于SMJ影响的超前性，因此它在东亚夏季气候预测上 有重要意义.     

Extreme precipitation events in East China and associated moisture transport pathways

Interannual variation of summer precipitation in East China, and frequency of rainstorms during the monsoon season from 1961 to 2010, are analyzed in this study. It is found that the two variables show opposite trends on a decadal time scale: frequency of rainstorms increases significantly after the 1990s, while summer precipitation in East China decreases during the same period. Analysis of the spatial distribution of summer rainstorm frequency from 1961 to 2010 indicates that it decreases from the southeast to the northwest at the east edge of the large-scale topography associated with the plateaus. Spatial distribution of rainstorms with daily rainfall greater than 50 mm is characterized by a “high in the southeast and low in the northwest” pattern, similar to the staircase distribution of the topography. However, the spatial distribution of variation in both summer precipitation and frequency of extreme rainstorms under global warming differs significantly from the three-step staircase topography. It is shown that moisture characteristics of summer precipitation and extreme rainstorms during the monsoon season in East China, including moisture transport pathways, moist flow pattern, and spatial structure of the merging area of moist flows, differ significantly. Areas of frequent rainstorms include the Yangtze River Valley and South China. Column- integrated moisture transport and its spatial structure could be summarized as a “merging” of three branches of intense moist flows from low and middle latitude oceans, and “convergence” of column-integrated moisture fluxes. The merging area for moist flow associated with rainstorms in the high frequency region is located slightly to the south of the monsoonal precipitation or non-rainstorm precipitation, with significantly strong moisture convergence. In addition, the summer moist flow pattern in East China has a great influence on the frequency of extreme rainstorms. Moisture flux vectors in the region of frequent rainstorms correspond to vortical flow pattern. A comparison of moisture flux vectors associated with non-rainstorms and rainstorms indicates that the moist vortex associated with rainstorms is smaller in size and located to the south of the precipitation maximum, while the moist vortex associated with non-rainstorms is larger and located to the north. It is shown that column- integrated moist transport vortices and the structure of moist flux convergence have significant impacts on the north-south oscillation of frequent rainstorm areas in East China, which is synchronized with the maximum vorticity of moisture transport and the minimum of convergence on the decadal time scale. Synthesis of moisture transport pathways and related circulation impacts leads to a conceptual model of moisture flow associated with rainstorms.     

An overview of the influence of atmospheric circulation on the climate in arid and semi-arid region of Central and East Asia

The arid and semi-arid (ASA) region of Asia occupies a large area in the middle latitudes of the Northern Hemisphere, of which the main body is the ASA region of Central and East Asia (CEA). In this region, the climate is fragile and the environment is sensitive. The eastern part of the ASA region of CEA is located in the marginal zone of the East Asian monsoon and is jointly influenced by westerly circulation and the monsoon system, while in the western part of the ASA of CEA, the climate is mainly controlled by westerly circulation. To understand and predict the climate over this region, it is necessary to investigate the influence of general circulation on the climate system over the ASA region of CEA. In this paper, recent progress in understanding the relationship between the general circulation and climate change over the ASA region is systematically reviewed. Previous studies have demonstrated that atmospheric circulation represents a significant factor in climate change over the ASA region of CEA. In the years with a strong East Asian summer monsoon, the water vapor flux increases and precipitation is abundant in the southeastern part of Northwest China. The opposite situation occurs in years when the East Asian summer monsoon is weak. With the weakening of the East Asian summer monsoon, the climate tends to dry over the semi-arid region located in the monsoon marginal zone. Recently, owing to the strengthening of the South Asian monsoon, more water vapor has been transported to the ASA region of Asia. The Plateau summer monsoon intensity and the precipitation in summer exhibit a significant positive correlation in Central Asia but a negative correlation in North China and Mongolia. A significant positive correlation also exists between the westerly index and the temperature over the arid region of CEA. The change in the westerly circulation may be the main factor affecting precipitation over the arid region of Central Asia.     

南半球环流异常与长江中下游夏季旱涝的关系

本文对长江中下游夏季旱涝年前期（3、4、5月的季节平均）和同期（6、7、8月的季节平均）的南半球环流作对比分析,探讨南半球环流异常与长江中下游夏季旱涝的关系. 结果表明前期和同期南半球环流均有显著差异,春季南极涛动对长江中下游旱涝的影响较夏季显著,南半球副热带高压在春、夏两季中有很好季节持续性. 因此,春季南半球环流异常可以作为长江中下游夏季旱涝主要短期气候预测因子. 南、北半球中高纬环流相互作用是长江中下游夏季降水的一个重要因素,其可能的联系机制是从南半球高纬到北半球东亚沿岸经向分布的正压遥相关. 研究中还发现在长江中下游的涝年,整个对流层中南半球春、夏两季有持续增温,这说明了南北半球的温度梯度减弱也是东亚夏季风减弱的原因之一.     

BCC_CSM1.1(m)模式对于夏季亚洲-太平洋涛动的模拟

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结合淮河流域平原区水文地质条件,阐述了淮河流域平原区铁锰元素在浅层地下水（埋深0～50 m）中的赋存特征和分布规律.结合前人研究成果并总结现有水质资料,认为淮河流域地下水中铁锰的形成和分布特征除了受含水介质成分、上覆土层性质、酸碱条件等影响外,主要受氧化还原环境控制.建议通过适当除铁锰工艺或改变地下水循环条件等方式来改变研究区浅层水地下水水质状况.     

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