中国西南汛期降水的振动和分布及其与印度洋海温异常的关系

用自然正交函数展开方法对1961－1995年西南汛期（6－8月）降水大尺度变化特征进行了分析，并在此基础上用典型相关分析方法研究了1－8月印度洋海温距平场与西南汛期降水场的遥相关分布特征，结果表明：西南汛期降水的地域差异显著，年际和年代际变化明显，其变化与印度洋海温变化有一定联系，分析还进一步表明，当印度洋海温呈某种特定的配置时，特别是南印度洋中西部海温的异常变化对西南汛期降水的发觉分布有一定作用，揭示了印度洋海温变化在西南汛期降水异常分布中的信号现象，说明特定的印度洋海温分布可以作为西南汛期旱涝预报的信号因子。     

不同区域海温异常对中国夏季旱涝影响的诊断研究和预测试验

利用季降水异常的典型集合相关预测模式, 研究了前期和同期不同季节全球海表温度距平场与中国夏季旱涝的遥相关分布特征以及这种相关型随季节的变化, 揭示了全球海温的异常变化在中国夏季旱涝中的信号特征.研究表明, 全球不同区域海温对我国夏季降水的影响存在着明显的季节差异.全球特定的海温分布可以作为中国夏季旱涝预报的信号因子.选取不同区域及不同时段的海温场作为因子场分别对1998、 1999年这两个典型年份的我国夏季降水进行了诊断研究和预测试验, 并通过不同区域海温的影响权重做集成预测.试验结果表明:不同区域海温的集成预测不仅可以有效地提高预测的准确性, 而且可以揭示不同时段不同区域海温的异常变化在夏季旱涝中的强信号现象.     

不同季节海温与中国夏季降水的时空特征分析

利用季降水异常的典型集合相关降水模式,分析了不同时段和不同区域的海温场与我国夏季（6～8月）降水之间的时空分布特征。结果表明：各大洋区海温存在着明显的季节、年际和年代际变化。与中国夏季降水相联系的印度洋海温的分布特征与季节有关,存在明显的偶极和单极分布形式,这种海温的异常变化对我国夏季纬向或经向雨带有一定的影响,全球特定的海温分布可以作为中国夏季旱涝预报的信号因子。不同季节海温和中国夏季降水在1970年代末都经历了一次突变,说明海温的季节差异对中国夏季降水的影响明显地受到海洋年代际基本态的制约。     

印度洋地区异常海温的偶极振荡与中国降水及温度的关系

利用1951-1997年近47年的印度洋海温距平场资料以及相应中国160站降水资料，通过相关普查得出，印度洋地区东西海温的偶极振荡与中国6-8月汛期的降水有较好的相关关系，特别是前期3-5月份的印度洋地区东西海温的偶极指数与中国6-8月降水的相关较好。分析1958-1995年NCEP 500hPa北半球高度场资料发现，印度洋偶极指数与欧亚中高纬度地区的高度场异常有密切的联系，其中印度洋偶极指数IODI负位相年有明显的PJ波列存在，印度洋偶极海湿异常很可能是通过PJ波列来影响中国的降水。同时，对印度洋地区海温偶极指数和中国地区温度的相关分析表明，印度洋地区海温偶极指数与冬季中国南部地区的温度也有较好的相关关系。     

太平洋和印度洋5月海温变化与我国汛期降水的关系研究

通过对近半个世纪以来太平洋和印度洋海温变化趋势分析,根据海温异常变化,选取5月太平洋区域(135°～171°E,25°～39°N)和印度洋区域(71°～107°E,25°～39°S)的海温变化指数,与中国汛期降水进行相关分析.结果表明,太平洋和印度洋对中国汛期降水的影响存在很大差别,太平洋的影响大于印度洋的影响,初步建立了一个太平洋和印度洋5月海温变化与中国汛期降水分布的物理概念模型.     

印度洋海温的偶极振荡与高原汛期降水和温度的关系

利用1961—2000年近40年印度洋海温距平场资料及对应的青藏高原35个观测站的降水与温度资料,通过相关普查得出,印度洋地区东西海温的偶极振荡与青藏高原汛期降水、温度有较好的相关关系,特别是前期1月、12月～2月的印度洋地区东西海温的偶极指数与青藏高原汛期(6～8月)降水和前一年6月的印度洋地区东西海温的偶极指数与青藏高原汛期(6～8月)温度有很好的相关。分析1961—2002年NCEP／NCAR 500hPa北半球高度场资料发现,印度洋地区东西海温的偶极指数与欧亚500hPa的高度场异常有密切的关系,并通过印度西南季风的强弱,影响到青藏高原汛期降水和温度的变化。     

赤道中印度洋夏季变温对中国夏季降水影响的数值模拟

利用大气环流模式模拟了赤道中印度洋海区夏季变温与海温本身异常对中国夏季降水的影响.结果表明:当该海区夏季正(负)海温距平值呈递增(递减)变化时,激发出的降水场的正(负)异常幅度比正(负)海温距平强迫下相应的降水场的正(负)异常幅度大;但当正(负)海温距平呈递减(递增)趋势变化时,激发出的降水异常场与正(负)海温距平强迫下相应的降水异常场的分布形势类似(不同),异常幅度也有所差异.夏季中印度洋不同类型的海温异常对大气加热的不同,导致东亚季风和印度季风的不同变异,暖海温异常下引起东亚季风的明显偏强,而冷海温异常下引起印度季风的明显偏强.     

El Nio期间印度洋海温异常对 亚洲气候的影响

El Nio事件发生时,赤道东太平洋海温出现高达2～3 ℃的正异常,同时,印度洋海温也会出现异常。但每次El Nio事件期间,印度洋异常海温的结构是不相同的,翘翘板型的海表温度结构,是印度洋海温异常的一种典型分布。利用IAP-GCM 9L模式,我们对El Nio期间,印度洋东冷西暖异常海温分布对气候的影响,特别是对亚洲气候的影响,作了数值模拟研究。模拟研究的结果表明,印度洋海温主要影响孟加拉湾、中南半岛、印尼、印度次大陆及中国大陆南部地区的气候变化。在El Nio发生期间,东冷西暖的印度洋海温结构,加大了东太平洋海温异常给东亚季风区带来的影响,它使中南半岛到印尼更加干旱,中国华北到山东半岛的降水减少,而使中国西南到华南的降水明显增加。在其影响下,东亚地区的雨带呈纬向分布,形成旱涝相间的纬向带状异常分布型,使模式模拟结果与中国旱涝的实际分布更加接近。同时,在对高度场、流场的分析中可以看到,印度洋东冷西暖海温分布使夏季副高位置偏南,印度洋到南海的西南风减弱,在中国西南到华南为气旋性环流控制,这些特征与降水分布是一致的。模拟试验表明,印度洋海温异常对我国El Nio期间降水异常的分布型有重要影响。     

汉江流域秋汛期典型旱涝年与前期海温的关系研究

利用汉江流域16个气象观测台站1961—2010年秋汛期(9—10月)逐候降水资料,计算了降水集中度(PCD)和集中期(PCP),并建立了相应的序列,结合秋汛期降水距平百分率,确定汉江流域秋汛期典型旱涝年。同时,利用美国国家环境预测中心及国家大气研究中心(NCEP/NCAR)提供的同期海温和500 hPa高度场资料,采用合成和相关分析方法,探讨了典型旱涝年与前期海温的关系。结果表明,印度洋、赤道中太平洋、北太平洋为3个海温关键区,当这3个海区海温发生异常时,影响汉江流域秋雨的主要系统(印缅槽、贝湖槽、东西伯利亚高压和乌拉尔山高压)也相应发生变化,从而导致PCD和降雨量异常,引发汉江流域洪涝或干旱灾害。在一定程度上,可将前期海温异常作为判断汉江流域秋汛期降水量多少及PCD强弱的前兆信号。     

影响陕西汛期降水空间分布的强信号

为了寻找影响陕西省汛期降水空间分布的前期强信号,应用陕西省1959～2003年36个气象代表站汛期(6～9月)降水量标准化资料,进行经验正交EOF分解.根据特征向量分布,确定陕西汛期降水典型分布场为"全省一致"型、"南北振荡"型和由北向南的"两头多(少)、中间少(多)"型.通过分析关键区的海温异常和大气环流变化等因子与EOF分解前3个时间系数的相关性,得到了汛期降水预测的一些重要前期强信号,如西风漂流区海温,Nion 3区海温、北太平洋涛动、东亚冬季风等,对陕西汛期降水分布预测具有明显的预示作用.     

降水对热带海表温度异常的邻域响应 I．数值模拟

基于低阶大气环流谱模式，本文设计了太平洋及印度洋４个不同海域的海表温度异常试验，去研究大气环流及降水对热带海表温度异常强迫作用的“同时”性响应。结果表明尽管暖性的海表温度异常均激发出低空辐合及高空辐散，但在不同海域所激发的异常流场却差异甚大。不过降水异常均发生在海表温度异常区及其毗邻处。它在对称的ＳＳＴＡ区的分布一般是非对称的。对水汽收支的分解分析表明，海表温度异常区异常降水的大小主要由异常的低空辐合决定，而异常降水的分布形态则由异常的水汽平流过程所决定。由于异常的低空辐合及异常的水汽平流过程主要发生在海表温度异常区及毗邻处，因此，降水对热带海表温度异常的响应基本Ｌ是一种邻域响应。它发生在气候平均低空气流沿海表温度异常的下风方向，或在海表温度异常所激发的低空异常气流沿气候平均海温降低的方向。     

Regimes of seasonal air–sea interaction and implications for performance of forced simulations

Sea surface temperature (SST) anomalies can induce anomalous convection through surface evaporation and low-level moisture convergence. This SST forcing of the atmosphere is indicated in a positive local rainfall–SST correlation. Anomalous convection can feedback on SST through cloud-radiation and wind-evaporation effects and wind-induced oceanic mixing and upwelling. These atmospheric feedbacks are reflected in a negative local rainfall–SST tendency correlation. As such, the simultaneous rainfall–SST and rainfall–SST tendency correlations can indicate the nature of local air–sea interactions. Based on the magnitude of simultaneous rainfall–SST and rainfall–SST tendency correlations, the present study identifies three distinct regimes of local air–sea interactions. The relative importance of SST forcing and atmospheric forcing differs in these regimes. In the equatorial central-eastern Pacific and, to a smaller degree, in the western equatorial Indian Ocean, SST forcing dominates throughout the year and the surface heat flux acts mainly as a damping term. In the tropical Indo-western Pacific Ocean regions, SST forcing and atmospheric forcing dominate alternatively in different seasons. Atmospheric forcing dominates in the local warm/rainy season. SST forcing dominates with a positive wind-evaporation feedback during the transition to the cold/dry season. SST forcing also dominates during the transition to the warm/rainy season but with a negative cloud-radiation feedback. The performance of atmospheric general circulation model simulations forced by observed SST is closely linked to the regime of air–sea interaction. The forced simulations have good performance when SST forcing dominates. The performance is low or poor when atmospheric forcing dominates.     

Delayed Atmospheric Temperature Response to ENSO SST： Role of High SST and the Western Pacific

Tropical zonally symmetric atmospheric warming occurs during ENSO’s warm phase, and lags the equa- torial east Pacific sea surface temperatures (SSTs) by 3–4 months. The role of the Indian and Atlantic oceans on the atmospheric delayed response has been pointed out by earlier studies. For 1951–2004, a regression analysis based on the observed SST data shows the western Pacific has a similarly important role as the Indian and Atlantic. Nevertheless, there is time mismatch of around 1–2 months between the zon...     

Effects of meridional sea surface temperature changes on stratospheric temperature and circulation

Using a state-of-the-art chemistry-climate model,we analyzed the atmospheric responses to increases in sea surface temperature （SST）.The results showed that increases in SST and the SST meridional gradient could intensify the subtropical westerly jets and significantly weaken the northern polar vortex.In the model runs,global uniform SST increases produced a more significant impact on the southern stratosphere than the northern stratosphere,while SST gradient increases produced a more significant impact on the northern stratosphere.The asymmetric responses of the northern and southern polar stratosphere to SST meridional gradient changes were found to be mainly due to different wave properties and transmissions in the northern and southern atmosphere.Although SST increases may give rise to stronger waves,the results showed that the effect of SST increases on the vertical propagation of tropospheric waves into the stratosphere will vary with height and latitude and be sensitive to SST meridional gradient changes.Both uniform and non-uniform SST increases accelerated the large-scale Brewer-Dobson circulation （BDC）,but the gradient increases of SST between 60°S and 60°N resulted in younger mean age-of-air in the stratosphere and a larger increase in tropical upwelling,with a much higher tropopause than from a global uniform 1.0 K SST increase.     

Numerical Simulation of the Effect of the SST Anomalies in the Tropical Western Pacific on the Blocking Highs over the Northeastern Asia

The effects of the sea surface temperature (SST) anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are simulated by the IAP-GCM with an observed and idealized distributions of the SST anomalies in the tropical western Pacific,respectively.Firstly,the atmospheric circulation anomalies during July and August,1980 are simulated by three anomalous experiments including the global SST anomaly experiment,the tropical SST anomaly experiment and the extratropical SST anomaly experiment,using the observed SST anomalies in 1980.It is shown that the SST anomalies in the tropical ocean greatly influence the formation and maintenance of the blocking high over the northeastern Asia,and may play a more important role than the SST anomalies in the extratropical ocean in the influence on the atmospheric circulation anomalies.Secondly,the effects of the SST anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are also simulated w     

Intensified impact of northern tropical Atlantic SST on tropical cyclogenesis frequency over the western North Pacific after the late 1980s

Previous studies suggest that spring SST anomalies over the northern tropical Atlantic(NTA) affect the tropical cyclone(TC) activity over the western North Pacific(WNP) in the following summer and fall. The present study reveals that the connection between spring NTA SST and following summer–fall WNP TC genesis frequency is not stationary. The influence of spring NTA SST on following summer–fall WNP TC genesis frequency is weak and insignificant before, but strong and significant after, the late 1980 s. Before the late 1980 s, the NTA SST anomaly-induced SST anomalies in the tropical central Pacific are weak, and the response of atmospheric circulation over the WNP is not strong. As a result, the connection between spring NTA SST and following summer–fall WNP TC genesis frequency is insignificant in the former period. In contrast,after the late 1980 s, NTA SST anomalies induce pronounced tropical central Pacific SST anomalies through an Atlantic–Pacific teleconnection. Tropical central Pacific SST anomalies further induce favorable conditions for WNP TC genesis,including vertical motion, mid-level relative humidity, and vertical zonal wind shear. Hence, the connection between NTA SST and WNP TC genesis frequency is significant in the recent period. Further analysis shows that the interdecadal change in the connection between spring NTA SST and following summer–fall WNP TC genesis frequency may be related to the climatological SST change over the NTA region.     

海温异常对江淮流域入梅的影响

通过对江淮流域入梅期与海温场的相关分析，以及对海温异常年大气环流的合成分析，研究了海温异常对江淮流域入梅的影响。结果表明，太平洋、印度洋和大西洋的海温异常对江淮流域的入梅期有较大影响，前一年11月至当年6月西太平洋暖池的海温偏高（低）时，江淮流域入梅早（晚）。2~5月中太平洋的海温偏高时，江淮流域入梅偏晚。5~6月，马斯克林高压附近的海温对入梅期有较好的指示意义，高海温对应早入梅，而低海温对应晚入梅。2~4月以及2~5月西太平洋暖池附近的海温对江淮流域的入梅也有较好的指示意义。6月，台湾以东以及南大西洋的海温异常对入梅期有较大影响。     

太平洋区域海温跃变及其与东亚夏季风的关系

本文利用英国气象局提供的全球SST月平均资料和NCAR／NCEP提供的500百帕高度场资料，分析了全球SSTA的年际和年代际变化，发现夏季全球SST在70年代发生了一次跃变，尤其北太平洋区域SST在1976年前后，由正距平变为负跨燕，并且跃变前后东亚夏季风也发了显著变化，我国汛期降水异常形势成相反分布，海温对东亚夏季风的影响途径和机制也发生了改变，1976年以前北太平洋区域海温起主要作用，跃变后，北太平洋区域海温异常与东亚夏季风关系变得不明显，而赤道中东太平洋海温的作用变得异常重要。     

Influences of Tidal Fronts on Coastal Winds Over an Inland Sea

A regional numerical model of the atmosphere was applied to an inland sea, the Seto Inland Sea in Japan, to study the influence of sea-surface temperature (SST) variations, accompanied by a tidal front, on the coastal winds in summer when tidal fronts fully develop. After confirmation of the model performance, two sensitivity simulations, which used spatially uniform SST with the highest and lowest values over the study area, were performed. The control and sensitivity simulations show that the mean wind speeds were apparently reduced by the low SST and the SST gradient accompanying the tidal front. The comparison of the terms in the momentum equations in control and sensitivity simulations indicates that the change of the perturbation pressure gradient force with the SST gradient is the most important factor in the modification of near-surface winds with SST variations. When the air flows across a tidal front, the air cools over the low SST area and warms over the high SST area. Consequently, the surface perturbation pressure increases over the low SST area and decreases over the high SST area. This adjustment in surface perturbation pressure produces an additional pressure gradient force with direction from the low SST area to the high SST area that decelerates the surface wind in the area upwind of the tidal front and accelerates the surface wind downwind of the tidal front.     

The sensitivity of sub-Saharan precipitation to Atlantic SST

The climate model of the Goddard Institute for Space Studies (Hansen et al., 1983) is used to study the sensitivity of sub-Saharan rainfall to Atlantic Ocean SST. Initial changes of SST in the South Atlantic Ocean on March 1st are shown to reduce the June–August sub-Saharan precipitation totals using the model version with an interactive ocean that updates SST. Evidence is offered in support of theories that link Sahel drought with anomalously warm SST in the eastern South Atlantic and the study compares the model's response to spatially coherent SST anomalies with the response to random SST perturbations. The physical processes whereby SST and sea-level pressure synoptics influence the African summer monsoon are discussed in reference to the simulations. Predictibility of Sahel summer rainfall based on spring SST patterns or spring atmospheric circulation patterns is implied by the results. The SST/Sahel drought links are discussed for projections of future climate characteristics.