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1.
Based on numerical simulation, this study explored the characteristics and interactions of surface sensible heating and atmospheric latent heating over the main part of the Tibetan Plateau, i.e., terrain at elevations >2 km in summer. The impacts of these two types of heating on local vertical motion and monsoonal meridional circulation were compared. Theoretical analysis and numerical experimentation demonstrated that by changing the configuration of the upper-tropospheric air temperature and circulation, the two types of heating could generate both minimum absolute vorticity and abnormal potential vorticity forcing near the tropopause, enhance the meridional circulation of the Asian summer monsoon, and produce an eastward- propagating Rossby wave train within the mid-latitude westerly flow. Consequently, the manifestations of these features were shown to influence the circulation of the Northern Hemisphere. 相似文献
2.
Influence of land evapotranspiration on climate variations 总被引：1，自引：0，他引：1
A coupled numerical model of the global atmosphere with a qualified biosphere (GOALS/LASG) has been used to assess the nature
of the physical mechanisms for land-atmosphere interactions, and the impacts of the Asian/North American land-surface evapotranspiration
on the regional and global climate. This sensitivity study suggests that the simulated climate would be relatively sensitive
to land surface evapotranspiration, especially over the Asian regions. The removal of evapotranspiration in Asia would create
a warmer and drier climate to a certain degree. Furthermore, the surface evapotranspiration anomalies would make a substantial
contribution to the formation and variation of subtropical anticyclones through the changes in monsoon precipitation and the
β -effect, but also make a large contribution to the variations of the atmospheric circulation in the Northern Hemisphere
and even the globe. Therefore, besides the traditional perception that we have generally emphasized on the influence of subtropical
anticyclones activities on the boreal summer precipitation over the regions of eastern China, the surface evapotranspiration
anomalies, however, also have substantial impacts on the subtropical anticyclones through the changes in monsoon precipitation.
For this reason, the variation in the internal heating sources of the atmosphere caused by the land surface evapotranspiration
and the vapor phase change during the boreal summer is an important external factor forcing the weather and climate. 相似文献
3.
An overview of the influence of atmospheric circulation on the climate in arid and semi-arid region of Central and East Asia 总被引：1，自引：0，他引：1
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. 相似文献
4.
The evolution and driving mechanism of the Asian winter monsoon system are of great importance to understanding the present-day climate. Through high-resolution particle size analysis of the oldest loess-red clay sequence known so far (with a basal age of about 8 Ma) and comparison of the results with oxygen isotope curves from North Atlantic marine sediments, 4 stages of the evolution of the Asian winter monsoon were clearly demonstrated. During the first stage, between about 8.1 and 4.3 Ma, there was no relation between Asian winter monsoon and Northern Hemisphere ice volume and high latitude climate inferred from marine sediments. A weak relation developed during the second stage, about 4.3 to 3.5 Ma. During the third stage (3.5 to 2.6 Ma) an Asian winter monsoon system similar to the present formed, initiating a stronger relation between the winter monsoon and Northern Hemisphere ice volume and high latitude climate. In the final stage (2.6 to 0 Ma) the present Asian winter monsoon system was fortified and stabilized and changes in the winter monsoon system were almost in phase with Northern Hemisphere ice volume and climate. The staggered uplift of Tibetan Plateau at ≈8, 3.6, 2.6 Ma and later might be the driving force for the evolution of the Asian winter monsoon.
相似文献5.
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. 相似文献
6.
亚洲-太平洋涛动是北半球夏季亚洲大陆和北太平洋副热带地区对流层中高层扰动温度场上大尺度的东西反相的遥相关现象，其异常变化与亚洲-太平洋地区夏季风气候有着密切的联系.基于欧洲中心的ERA-40再分析资料和国家气候中心BCC_CSM1.1（m）气候系统模式多年的数值模拟结果，本文主要评估了BCC_CSM1.1（m）模式对于夏季亚洲-太平洋涛动的空间分布、指数的时间演变及与其变化所对应的亚洲地区夏季环流异常等方面的模拟能力，结果表明：BCC_CSM1.1（m）模式能够较好地模拟出北半球夏季对流层中高层扰动温度在亚-太地区中纬度存在的西高东低"跷跷板"现象；模式能够模拟出夏季亚洲-太平洋涛动指数的年际变率，但是不能模拟出该指数在20世纪60-70年代明显下降的年代际趋势；模式还能较好地模拟出亚洲-太平洋涛动高低指数年亚洲-太平洋地区夏季环流的异常：指数偏高年份，南亚高压增强，高空西风急流带和热带东风急流均加强，索马里越赤道气流增强，南亚热带季风和东亚副热带季风均增强，东亚季风低压槽加强，西北太平洋副热带高压增强，南亚和东亚北部降水增加，菲律宾地区、中国长江流域-朝鲜半岛-日本一带地区降水减少，反之亦然. 相似文献
7.
Monsoon and arid regions in the Asia-Africa-Australia(A-A-A) realm occupy more than 60% of the total area of these continents. Geological evidence showed that significant changes occurred to the A-A-A environments of the monsoon and arid regions, the land-ocean configuration in the Eastern Hemisphere, and the topography of the Tibetan Plateau(TP) in the Cenozoic. Motivated by this background, numerical experiments for 5 typical geological periods during the Cenozoic were conducted using a coupled ocean-atmosphere general circulation model to systemically explore the formations and evolutionary histories of the Cenozoic A-A-A monsoon and arid regions under the influences of continental drift and plateau uplift. Results of the numerical experiments indicate that the timings and causes of the formations of monsoon and arid regions in the A-A-A realm were very different. The northern and southern African monsoons existed during the mid-Paleocene, while the South Asian monsoon appeared in the Eocene after the Indian Subcontinent moved into the tropical Northern Hemisphere. In contrast, the East Asian monsoon and northern Australian monsoon were established much later in the Miocene. The establishment of the tropical monsoons in northern and southern Africa, South Asia, and Australia were determined by both the continental drift and seasonal migration of the Inter-Tropical Convergence Zone(ITCZ), while the position and height of the TP were the key factor for the establishment of the East Asian monsoon. The presence of the subtropical arid regions in northern and southern Africa,Asia, and Australia depended on the positions of the continents and the control of the planetary scale subtropical high pressure zones, while the arid regions in the Arabian Peninsula and West Asia were closely related to the retreat of the Paratethys Sea. The formation of the mid-latitude arid region in the Asian interior, on the other hand, was the consequence of the uplift of the TP.These results from this study provide insight to the important roles played by the earth's tectonic boundary conditions in the formations and evolutions of regional climates during geological times. 相似文献
8.
Heinz Wanner Stefan Brönnimann Carlo Casty Dimitrios Gyalistras Jürg Luterbacher Christoph Schmutz David B. Stephenson Eleni Xoplaki 《Surveys in Geophysics》2001,22(4):321-381
This paper aims to provide a comprehensive review of previous studies and concepts concerning the North Atlantic Oscillation. The North Atlantic Oscillation (NAO) and its recent homologue, the Arctic Oscillation/Northern Hemisphere annular mode (AO/NAM), are the most prominent modes of variability in the Northern Hemisphere winter climate. The NAO teleconnection is characterised by a meridional displacement of atmospheric mass over the North Atlantic area. Its state is usually expressed by the standardised air pressure difference between the Azores High and the Iceland Low. ThisNAO index is a measure of the strength of the westerly flow (positive with strong westerlies, and vice versa). Together with the El Niño/Southern Oscillation (ENSO) phenomenon, the NAO is a major source of seasonal to interdecadal variability in the global atmosphere. On interannual and shorter time scales, the NAO dynamics can be explained as a purely internal mode of variability of the atmospheric circulation. Interdecadal variability maybe influenced, however, by ocean and sea-ice processes. 相似文献
9.
应用日本东京大学气候系统研究中心(CCSR)发展起来的一个全球大气环流谱模式(T42L200版本),对l998年夏季气候异常和大气环流的预测问题进行了研究,定量地检查了该模式对夏季降水和大气环流异常的预测准确度.说明该模式对1998年的预测水平是比较高的;并证实大气环流在春季的初始异常对北半球夏季大气环流和降水异常起了很重要的作用,而对南半球的作用则小得多.就中国长江流域1998年的降水异常而言,初始环流的作用约占50%. 相似文献
10.
Antecedent anomalies of sea surface temperature and atmospheric circulation are important signals for making long-term streamflow forecasts. In this study, four groups of ocean-atmospheric indices, i.e, El Niño Southern Oscillation (ENSO), the Northern Hemisphere atmospheric circulation, the Southern Hemisphere atmospheric circulation (SAC), and the Western Pacific and Indian Ocean SST (WPI), are evaluated for forecasting summer streamflow of the Yangtze River. The gradient boosting regression tree (GBRT) is used to forecast streamflow based on each group of indices. The score based on receiver operating characteristics (ROC) curves, i.e., area under the ROC curve (AUC), is used to evaluate skills of models for identifying the high category and the low category of summer streamflow. It is found that the ENSO group and the SAC group show higher AUC values. Furthermore, both AUC values of GBRT models and individual indices show that the low flow years are easier to be identified than the high flow years. The result of this study highlights the skill from the Southern Hemisphere circulation systems for forecasting summer streamflow of the Yangtze River. Results of relative influences of predictors in GBRT models and AUC of individual indices indicate some key ocean-atmospheric indices, such as the Multivariate ENSO Index and the 500-hPa height of the east of Australia. 相似文献
11.
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. 相似文献
12.
Qing He Kwok Pan Chun Mou Leong Tan Bastien Dieppois Liew Juneng Julian Klaus Matthieu Fournier Nicolas Massei Omer Yetemen 《水文研究》2021,35(9):e14356
Ocean–atmosphere modes of climate variability in the Pacific and Indian oceans, as well as monsoons, regulate the regional wet and dry episodes in tropical regions. However, how those modes of climate variability, and their interactions, lead to spatial differences in drought patterns over tropical Asia at seasonal to interannual time scales remains unclear. This study aims to analyse the hydroclimate processes for both short- and long-term spatial drought patterns (3-, 6, 12- and 24-months) over Peninsular Malaysia using the Standardized Precipitation Index, Standardized Precipitation Evapotranspiration Index, and Palmer Drought Severity Index. Besides that, a generalized least squares regression is used to explore underlying circulation mechanisms of these spatio-temporal drought patterns. The tested drought indices indicate a tendency towards wetter conditions over Peninsular Malaysia. Based on principal component analysis, distinct spatio-temporal drought patterns are revealed, suggesting North–South and East–West gradients in drought distribution. The Pacific El Nino Southern Oscillation (ENSO), the South Western Indian Ocean (SWIO) variability, and the quasi-biennial oscillation (QBO) are significant contributors to the observed spatio-temporal variability in drought. Both the ENSO and the SWIO modulate the North–South gradient in drought conditions over Peninsular Malaysia, while the QBO contributes more to the East–West gradient. Through modulating regional moisture fluxes, the warm phases of the ENSO and the SWIO, and the western phases of the QBO weaken the southwest and northeast monsoon, leading to precipitation deficits and droughts over Peninsular Malaysia. The East–West or North–South gradients in droughts are related to the middle mountains blocking southwest and northeast moisture fluxes towards Peninsular Malaysia. In addition, the ENSO and QBO variations are significantly leading to short-term droughts (less than a year), while the SWIO is significantly associated with longer-duration droughts (2 years or more). Overall, this work demonstrates how spatio-temporal drought patterns in tropical regions are related to monsoons and moisture transports affected by the oscillations over the Pacific and Indian oceans, which is important for national water risk management. 相似文献
13.
利用高低层大气环流、OLR（向外长波辐射）、CMAP降水、SST（海表温度）等资料分析了孟加拉湾地区3—5月多年气候平均大气环流及不同要素的演变特征，定义了一个新的孟加拉湾夏季风（BOBSM，下同）爆发指标为孟加拉湾地区（5°N—15°N，90°E—97.5°E）850 hPa和200 hPa纬向风区域平均的变化同时满足U850 > 3 m·s-1和U200 < -5 m·s-1，并持续5天的第一天即作为BOBSM爆发日期.该季风指数有明确的天气学意义，可以反映孟加拉湾低层西南风持续稳定和南亚高压在青藏高原建立早晚的特征.文章进一步分析了BOBSM爆发的年际特征及其前兆海洋信号特征，结果表明：1981—2010年BOBSM爆发的平均日期为5月10日，季风爆发有显著的年际波动，爆发最早在1999年（4月11日）和最晚在1968年（6月1日），年代际尺度上表现为由爆发偏晚至偏早的变化趋势；BOBSM爆发早（晚）与热带印度洋地区850 hPa的越赤道气流和西风异常加强（减弱），以及200 hPa青藏高原南亚高压的季节性建立偏早（晚）等密切联系；前期冬季赤道西太平洋的海温冷（暖）变化对BOBSM爆发早（晚）有很好的指示意义，前期冬季海温偏高（低）有利于季风偏早（晚），其影响的主要途径是通过热源变化激发纬向垂直环流及其热带印度洋和太平洋低层环流异常，进而影响季风爆发早晚. 相似文献
14.
观测事实揭示,春季Hadley环流在年际时间尺度上与东亚夏季风环流和降水具有密切联系.在未来全球变暖背景下,春季Hadley环流与东亚夏季风环流和降水的这种年际关系是否会发生变化？针对该问题,本文在评估的基础上选取五个气候模式,分析了A1B排放情景下春季北半球Hadley环流年际变率的未来变化及其与东亚夏季风环流和降水的年际关系.多模式集合(MME)预估结果表明,在全球变暖背景下,与20世纪末期(1970—1999年)相比,到21世纪末期(2070—2099年),春季北半球Hadley环流的年际变率强度将减弱,减弱幅度达32%.随着春季Hadley环流年际变率的减弱,其与夏季西太平洋副热带高压和东亚夏季风强度的联系将变弱.MME模拟结果还显示,春季Hadley环流与夏季东亚西风急流和降水的关系也降低,但各单个模式间存在较大差异. 相似文献
15.
Arabian Peninsula-North Pacific Oscillation and its association with the Asian summer monsoon 总被引：2，自引：0，他引：2
Using correlation and EOF analyses on sea level pressure from 57-year NCEP-NCAR reanalysis data, the Arabian Peninsula-North Pacific Oscillation (APNPO) is identified. The APNPO reflects the co-variability between the North Pacific high and South Asian summer monsoon low. This teleconnec- tion pattern is closely related to the Asian summer monsoon. On interannual timescale, it co-varies with both the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM); on decadal timescale, it co-varies with the EASM: both exhibit two abrupt climate changes in the middle 1960s and the late 1970s respectively. The possible physical process for the connections between the APNPO and Asian summer monsoon is then explored by analyzing the APNPO-related atmospheric circulations. The results show that with a strong APNPO, the Somali Jet, SASM flow, EASM flow, and South Asian high are all enhanced, and an anomalous anticyclone is produced at the upper level over northeast China via a zonal wave train. Meanwhile, the moisture transportation to the Asian monsoon regions is also strengthened in a strong APNPO year, leading to a strong moisture convergence over India and northern China. All these changes of circulations and moisture conditions finally result in an anoma- lous Asian summer monsoon and monsoon rainfall over India and northern China. In addition, the APNPO has a good persistence from spring to summer. The spring APNPO is also significantly corre- lated with Asian summer monsoon variability. The spring APNPO might therefore provide valuable in- formation for the prediction of Asian summer monsoon. 相似文献
16.
本文应用欧洲中期预报中心（ECMWF,European Centre for Medium\|Range Weather Forecasts—ERA\|40）资料和美国国家环境预测中心和国家大气研究中心(NCEP/NCAR, National Centers for Environmental Prediction/National Center for Atmospheric Research)资料,研究了青藏高原雪深变化对南海夏季风爆发的影响和ENSO对青藏高原降雪的影响.结果表明：（1）ECMWF的雪深资料是可信的,可以用来研究青藏高原雪深变化对南海夏季风爆发的影响;（2）青藏高原的积雪异常影响到500 hPa以上的温度异常和印度洋与大陆间的气温对比,一方面使上层的南亚高压移动速度发生变化,另一方面也影响到低层大气的运动和东西向风异常,在青藏高原少雪年,东印度洋产生西风异常和一个气旋对,而在青藏高原多雪年,东印度洋产生东风异常和一个反气旋对;（3）ENSO与青藏高原春季积雪关系密切.东太平洋SST正异常时,东印度洋和南海气压偏高,从而导致该区海陆经向压强梯度增强和西风异常.另外,此时青藏高原北部气压偏高,北风偏强,副热带锋面增强,同时,印度洋的SST偏高,为青藏高原降雪提供了水汽保障,这些都有利于青藏高原的降雪. 相似文献
17.
青藏高原大地形的热力强迫作用对亚洲夏季风的形成和发展具有重要的影响.本文利用较高分辨率的WRF区域模式,探讨了高原不同区域(斜坡和平台)的地形加热分别对南亚夏季风和东亚夏季风的影响.结果表明:高原南部喜马拉雅山脉的斜坡地形加热对其周围局地的环流形势和降水影响十分明显,是南亚夏季风北支分量形成和维持的主导因子,也是斜坡上气流爬坡和降水发生的必要条件.斜坡加热对东亚夏季风也有明显的增强作用,它不仅加强了中国东部低空西南季风环流,还会造成北部南下的异常干冷空气的响应.斜坡上的地形加热作用也是对流层高层暖中心位置维持在斜坡上空的一个重要原因.而高原平台加热对季风环流和降水的影响虽然没有喜马拉雅山脉斜坡加热那么显著,但是对南亚夏季风的影响范围更广,对经向哈得来环流影响更明显,能够调控高原以外更远处热带洋面上的西南季风环流.通过比较高原不同区域地形加热条件下的多种季风指数,进一步表明了高原地形加热对南亚和东亚夏季风均有增强作用,但是高原不同区域的地形加热对两类夏季风子系统又会产生不一样的影响. 相似文献
18.
观测事实揭示出春季Hadley环流与夏季西北太平洋热带气旋频数之间存在显著的负相关关系.由春季Hadley环流异常引起的西北太平洋地区夏季纬向风垂直切变、大气辐合辐散等的异常变化是这一关系存在的内在原因.本文通过数值试验对这一关系的真实性进行了验证,即利用中国科学院大气物理研究所发展的9层大气环流模式（IAP9L-AGCM）模拟了春季Hadley环流异常偏强情景,并分析了该情景下影响西北太平洋热带气旋生成的环境场的响应.结果表明,在春季Hadley环流偏强情景下,夏季西北太平洋地区纬向风垂直切变幅度加大,低空大气异常辐散,高空大气异常辐合,东亚夏季风减弱,这种环流背景不利于热带气旋生成和发展,因此,西北太平洋热带气旋频数异常偏少.数值模拟结果与已有的诊断结果相吻合,进而证实了春季Hadley环流与夏季西北太平洋热带气旋频数负相关关系的存在.因此,春季Hadley环流信号可以用于西北太平洋热带气旋活动的气候预测. 相似文献
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清华大学地球系统科学研究中心在一个标准耦合模式（SC）的基础上建立了交互集合耦合模式系统（IE）,该系统可以实现多个不同大气模式或者同一大气模式采取不同初值组成的多个分量集合之后与海、陆、冰模式进行耦合.本文利用同一大气模式七个不同初值分量与其它模式分量开展在线集合耦合试验,利用积分稳定之后100年的试验结果,分析了IE在减小海-气界面大气噪音的情况下,对北太平洋海表面温度（SST）变率和ENSO的模拟,并与SC模拟结果进行了对比.分析表明,IE减小了北太平洋中高纬度SST方差的85%以上,表明该区域SST变率主要受大气的影响,且主要是通过改变海表湍流热通量实现的.黑潮延伸体区和北太平洋中部副热带涡旋区域平均SST 8年左右的低频周期主要受来自大气内部动力过程的驱动.在集合耦合模拟中,无论是副热带涡旋区SST与ENSO的联系,还是ENSO与北太平洋中高纬度SST的联系都能模拟出来,而标准模式未能模拟出这些现象,意味着大气噪音过强将掩盖ENSO与太平洋热带外SST的联系.IE对与ENSO关联的“太平洋-北美”（PNA）遥相关型的合理模拟,并通过湍流热通量对海表温度的影响,是其能够更好模拟ENSO与北太平洋中高纬度SST关系的重要原因.本文通过分析验证了所建立的交互集合耦合模式系统的合理性,揭示了该系统在海-气相互作用研究领域方面具有一定应用前景. 相似文献
20.
Instability characteristics of the East Asian Monsoon recorded by high-resolution loess sections from the last interglacial (MIS5) 总被引：3，自引：0，他引：3
Guan QingYu Pan BaoTian Gao HongShan Li BingYuan Wang JunPing Su Huai 《中国科学D辑(英文版)》2007,50(7):1067-1075
The selection of high-resolution loess sections is needed in order to determine the climatic variability of the East Asian Monsoon during the last interglacial. Two sequences of S1 on the eastern and west-ern sides of the Liupan Mountain were both composed of five paleosol layers and four loess layers,indicating that there were five strong summer monsoon events and four strong winter monsoon events in MIS5. This corresponds with other records of the East Asian Monsoon,along with NGRIP and the North Atlantic records,implying that the climate of the Northern Hemisphere was very instable during the last interglacial. Two layers of paleosols and one layer of loess had developed during MIS5a and MIS5c. Compared with MIS5e,the climate in MIS5a and MIS5c fluctuated more intensively on a millen-nial scale,whereas the climate was relatively stable in MIS5e. 相似文献