共查询到18条相似文献，搜索用时 111 毫秒
1.
The Decadal Shift of the Summer Climate in the Late 1980s over Eastern China and Its Possible Causes 总被引：2，自引：0，他引：2 
下载免费PDF全文
下载免费PDF全文 In this paper, it is pointed out that a notable decadal shift of, the summer climate in eastern China occurred in the late 1980s. In association with this decadal climate shift, after the late 1980s more precipitation appeared in the southern region of eastern China （namely South China）, the western Pacific subtropical high stretched farther westward with a larger south-north extent, and a strengthened anticyclone at 850 hPa appeared in the northwestern Pacific. The decadal climate shift of the summer precipitation in South China was accompanied with decadal changes of the Eurasian snow cover in boreal spring and sea surface temperature （SST） in western North Pacific in boreal summer in the late 1980s. After the late 1980s, the spring Eurasian snow cover apparently became less and the summer SST in western North Pacific increased obviously, which were well correlated with the increase of the South China precipitation. The physical processes are also investigated on how the summer precipitation in China was affected by the spring Eurasian snow cover and summer SST in western North Pacific. The change of the spring Eurasian snow cover could excite a wave-train in higher latitudes, which lasted from spring to summer. Because of the wave-train, an abnormal high appeared over North China and a weak depression over South China, leading to more precipitation in South China. The increase of the summer SST in the western North Pacific reduced the land-sea thermal contrast and thus weakened the East Asian summer monsoon, also leading to more precipitation in South China. 相似文献
2.
Based on surface air temperature and precipitation observation data and NCEP/NCAR atmospheric reanalysis data,this study evaluates the prediction of East Asian summer climate during 1959–2016 undertaken by the CESM (Community Earth System Model) large-ensemble initialized decadal prediction (CESM-DPLE) project. The results demonstrate that CESM-DPLE can reasonably capture the basic features of the East Asian summer climate and associated main atmospheric circulation patterns. In general, the prediction skill is quite high for surface air temperature,but less so for precipitation, on the interannual timescale. CESM-DPLE reproduces the anomalies of mid-and highlatitude atmospheric circulation and the East Asian monsoon and climate reasonably well, all of which are attributed to the teleconnection wave train driven by the Atlantic Multidecadal Oscillation (AMO). A transition into the warm phase of the AMO after the late 1990s decreased the geopotential height and enhanced the strength of the monsoon in East Asia via the teleconnection wave train during summer, leading to excessive precipitation and warming over East Asia. Altogether, CESM-DPLE is capable of predicting the summer temperature in East Asia on the interannual timescale, as well as the interdecadal variations of East Asian summer climate associated with the transition of AMO phases in the late 1990s, albeit with certain inadequacies remaining. The CESM-DPLE project provides an important resource for investigating and predicting the East Asian climate on the interannual and decadal timescales. 相似文献
3.
A regional climate model is employed to simulate the aerosols(dust,sulfate,black carbon,and organic carbon) and their direct effect on the climate over China.The emphasis is on the direct radiative forcing due to the change in mixing state of aerosols.The results show that direct radiative forcing is significantly different between externally and internally mixed aerosols.At the top of the atmosphere(TOA),the radiative forcing of externally mixed aerosols is larger than that of internally mixed ones,especially in the Tarim desert region where the difference is about 0.7 W m 2.At the surface,however,the situation becomes opposite,especially in the Sichuan basin where the difference is about-1.4 W m 2.Nonetheless,either externally or internally mixed aerosols in China can result in a significant cooling effect,except for the warming in South China in winter and the slight warming in North China in February.The cooling effect induced by externally mixed aerosols is weaker than that induced by internally mixed aerosols,and this is more obvious in spring and winter than in summer and autumn.In spring and summer,the inhibiting effect of externally mixed aerosols on precipitation is less than that of internally mixed aerosols,whereas in autumn and winter the difference is not obvious. 相似文献
4.
Recent Progress in the Impact of the Tibetan Plateau on Climate in China 总被引：14，自引：0，他引：14
Studies of the impacts of the Tibetan Plateau （TP） on climate in China in the last four years are reviewed. It is reported that temperature and precipitation over the TP have increased during recent decades. From satellite data analysis, it is demonstrated that most of the precipitation over the TP is from deep convection clouds. Moreover, the huge TP mechanical forcing and extraordinary elevated thermal forcing impose remarkable impacts upon local circulation and global climate. In winter and spring, stream flow is deflected by a large obstacle and appears as an asymmetric dipole, making East Asia much colder than mid Asia in winter and forming persistent rainfall in late winter and early spring over South China. In late spring, TP heating contributes to the establishment and intensification of the South Asian high and the abrupt seasonal transition of the surrounding circulations. In summer, TP heating in conjunction with the TP air pump cause the deviating stream field to resemble a cyclonic spiral, converging towards and rising over the TP. Therefore, the prominent Asian monsoon climate over East Asia and the dry climate over mid Asia in summer are forced by both TP local forcing and Eurasian continental forcing.
Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast.
On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal （BOB） and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP lea 相似文献
Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast.
On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal （BOB） and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP lea 相似文献
5.
INTERDECADAL VARIATION OF THE RELATIONSHIP BETWEEN ENSO AND SUMMER INTERANNUAL CLIMATE VARIABILITY IN CHINA 总被引：2，自引：0，他引：2
Interdecadal variation of the relationships between ENSO and the summer interannual climate variability in China is investigated by using techniques of sliding correlation analysis with the tropical Pacific SSTA and the observed surface air temperature and precipitation from stations in China. The results indicate that there are stable and robust relations that the Northern China is relatively dry during the developing phase of ENSO while the Yangtze River valley is relatively wet during the decaying phase of ENSO. On the other hand, interdecadal variations of the relations are also found in other regions. Over the time both prior to the Pacific decadal climate shift (before the late 1970s) and after it (after the late 1970s), during the developing phases of ENSO the summer precipitation anomaly in South China changed from below to above normal, whereas that in Northeast China changed from above to below normal; the summer surface air temperature anomaly in North and Northeast China changed from cooling to warming, whereas that in South China changed to cooling; during the decaying phases of ENSO the North China changed from wetter to dryer while the Huai River valley changed from dryer to normal; North China, Yangtze River valley and South China tend to be warmer. Based on the composite analysis of the NCAR/NCEP reanalyze datasets, significant differences existing in ENSO-related atmospheric circulation anomaly in East Asia during pre- and post-shift periods may be responsible for the interdecadal variation of relationships between ENSO and surface air temperature and precipitation in China. 相似文献
6.
Assessing the Impacts of Initial Snow Conditions over the Tibetan Plateau on China Precipitation Prediction Using a Global Climate Model 下载免费PDF全文
下载免费PDF全文 CHEN Hong 《大气和海洋科学快报》2014,(2):81-86
Two ensemble experiments were conducted using a general atmospheric circulation model. These experiments were used to investigate the impacts of initial snow anomalies over the Tibetan Plateau（TP） on China precipitation prediction. In one of the experiments, the initial snow conditions over the TP were climatological values; while in the other experiment, the initial snow anomalies were snow depth estimates derived from the passive microwave remote-sensing data. In the current study, the difference between these two experiments was assessed to evaluate the impact of initial snow anomalies over the TP on simulated precipitation. The results indicated that the model simulation for precipitation over eastern China had certain improvements while applying a more realistic initial snow anomaly, especially for spring precipitation over Northeast China and North China and for summer precipitation over North China and Southeast China. The results suggest that seasonal prediction could be enhanced by using more realistic initial snow conditions over TP, and microwave remote-sensing snow data could be used to initialize climate models and improve the simulation of eastern China precipitation during spring and summer. Further analyses showed that higher snow anomalies over TP cooled the surface, resulting in lower near- surface air temperature over the TP in spring and summer. The surface cooling over TP weakened the Asian summer monsoon and brought more precipitation in South China in spring and more precipitation to Southeast China during summer. 相似文献
7.
The numerical simulation experiment of climate at Last Glacial Maximum (LGM.21 ka BP)in China is made by using an atmospheric general circulation model (AGCM) coupled with landsurface processes (AGCM SSiB) and earth orbital parameters and boundary forcing conditions at21 ka.The modeled climate features are compared with reconstructed conditions at 21 ka frompaleo-lake data and pollen data.The results show that the simulated climate conditions at 21 ka inChina are fairly comparable with paleo-climatological data.The climate features at 21 ka in Chinafrom the experiment are characterized by a drier in the east and a wetter in the west and in theTibetan Plateau as well.According to the analysis of distribution of pressure and precipitation,aswell as the intensity of atmospheric circulation at 21 ka,monsoon circulation in eastern Asia wassignificantly weak comparing with the present.In the Tibetan Plateau,the intensity of summermonsoon circulation was strengthened,and winter monsoon was a little stronger than the present.The simulation with given forcing boundary conditions,especially the different vegetationcoverage,can reproduce the climate condition at the LGM in China,and therefore providesdynamical mechanisms on the climate changes at 21 ka. 相似文献
8.
Temporal Variations of the Spring Persistent Rains and South China Sea Sub-high and Their Correlations to the Circulation and Precipitation of the East Asian Summer Monsoon 下载免费PDF全文
下载免费PDF全文 National Meteorological Information Center （NMIC） rainfall data and NCEP/NCAR daily circulation reanalysis data are employed to establish the onset-pentad time index of the spring persistent rains （SPR） and the decay-pentad time index of the South China Sea （SCS） sub-high. These indexes are used to study the relationship between the factors in SPR period and their relations to the circulation and precipitation of the East Asian summer monsoon （EASM）. Results show that, the summer rainfall over southeastern China decreases when SPR onset is late. For then EASM strengthens and the cyclonic circulation around the Tibetan Plateau （TP） strengthens, which makes abnormal anti-cyclonic circulation （cyclonic convergent circulation weakens） appear over southeastern China. When the decay of SCS sub-high delays, abnormal flood prevails over the middle and lower reaches of the Yangtze River （MLYR） and to the south. That is mainly caused by EASM weakening while SCS sub-high strengthening, then the abnormal southwesterly over South China and the abnormal northerlies of anti-cyclonic circulation around the TP converge over the Yangtze Valley. The two indexes have high correlations with multivariate ENSO index （MEI） in March, indicating that the climate abnormity in East Asia is related to global climate abnormity tightly. The two time indexes are independent of each other, which is favorable for the prediction of the anomalies of the circulation and precipitation of EASM. From this point of view, we must take the global climate background into account when we analyze and predict the East Asian summer circulation and precipitation. 相似文献
9.
Simulation of the radiative effect of black carbon aerosols and the regional climate responses over China 总被引：10，自引：0，他引：10
As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS,and the transport model of BC aerosols has also been established and combined with the RIEMS model.Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July. 相似文献
10.
RegCM4.3, a high-resolution regional climate model, which includes five kinds of aerosols(dust, sea salt,sulfate, black carbon and organic carbon), is employed to simulate the East Asian summer monsoon(EASM) from 1995 to 2010 and the simulation data are used to study the possible impact of natural and anthropogenic aerosols on EASM.The results show that the regional climate model can well simulate the EASM and the spatial and temporal distribution of aerosols. The EASM index is reduced by about 5% by the natural and anthropogenic aerosols and the monsoon onset time is also delayed by about a pentad except for Southeast China. The aerosols heat the middle atmosphere through absorbing solar radiation and the air column expands in Southeast China and its offshore areas. As a result, the geopotential height decreases and a cyclonic circulation anomaly is generated in the lower atmosphere. Northerly wind located in the west of cyclonic circulation weakens the low-level southerly wind in the EASM region. Negative surface radiative forcing due to aerosols causes downward motion and an indirect meridional circulation is formed with the low-level northerly wind and high-level southerly wind anomaly in the north of 25° N in the monsoon area, which weakens the vertical circulation of EASM. The summer precipitation of the monsoon region is significantly reduced,especially in North and Southwest China where the value of moisture flux divergence increases. 相似文献
11.
春夏东亚大气环流年代际转折的影响及其可能机理 总被引：2，自引：0，他引：2
本文通过多变量联合经验正交分解(MV-EOF)方法揭示了近30年(1979~2010年) 春季和夏季东亚大气环流所发生的年代际转折及其与中国南方降水年代际季节反相变化的内在联系,探讨了局地性大气热源年代际变化影响东亚大气环流年代际转折的可能机理.结果表明:(1)东亚大气环流春季第一模态和夏季第二模态在90年代中期都发生了明显的年代际转折;(2)与春季大气环流第一模态和夏季大气环流第二模态年代际转折相对应的是中国南方降水明显的年代际季节反相变化,即春季降水年代际减少,夏季降水年代际增多;(3)春季青藏高原和夏季贝加尔湖地区大气热源年代际变化对东亚大气环流年代际转折有一定贡献,是造成中国南方降水年代际季节反相变化的直接原因;(4)春季青藏高原大气热源的年代际减弱,使得高原东南侧的西南风减弱,导致中国南方上空水汽输送不足,春季降水减少.夏季贝加尔湖大气热源偶极型分布由“南负北正”转变为“南正北负”,由此在贝湖上空激发高压异常,使得夏季雨带北进受阻而停滞南方,造成中国南方夏季降水增多. 相似文献
12.
中国东部夏季气候20世纪80年代后期的年代际转型及其可能成因 总被引：27，自引：7，他引：20
指出了中国东部夏季气候在20世纪80年代末出现了一次明显的年代际气候转型.伴随着这次年代际转型,80年代末以后中国东部南方地区降水明显增多,500 hPa西太平洋副热带高压西伸且南北范围变大,西北太平洋上空850 hPa反气旋增强.中国东部夏季80年代后期出现南方多雨的年代际转型与欧亚大陆春季积雪、西北太平洋夏季海面温度的年代际变化存在密切联系,它们也都在80年代末出现年代际转型.从80年代末以后,伴随着欧亚大陆春季积雪明显减少和西北太平洋夏季海面温度明显增高,中国夏季南方降水明显增加.文中分析了欧亚大陆春季积雪和西北太平洋夏季海面温度影响中国降水的物理过程,指出欧亚大陆春季积雪能够在500 hPa激发出大气中的遥相关波列,所激发出的波列可以从春季一直持续到夏季,造成中国北方为高压控制,南方为微弱低压控制,使得降水出现在中国南方.西北太平洋夏季海面温度的升高能够减小海陆热力差异,使得夏季风减弱,导致中国南方地区降水增多. 相似文献
13.
全球变暖背景下,中国东部夏季降水在20世纪70年代末开始较19世纪呈现东北及长江中、下游地区多雨,华北及华南少雨的特征。与此同时,人类活动排放的CO2及气溶胶量也发生了明显的年代际变化。文中利用地球系统耦合模式（CESM）诊断了中国东部夏季的水分收支对人类活动排放的CO2及气溶胶年代际变化的响应。发现CO2排放量增加后,江淮流域的水汽辐合以及中国南方的水汽辐散主要是与质量辐散有关的动力项及与湿度梯度相关的热力项共同作用的结果,但动力作用更显著。气溶胶效应则主要通过动力作用使得江淮流域水汽辐合,而中国南方地区水汽辐散。虽然CO2和气溶胶对辐射量及温度的影响差别很大,但通过改变温度梯度,热成风效应产生的动力作用都会导致江淮流域上升运动增强,降水增多;而中国南方下沉运动显著,降水减少,与观测结果一致,且CO2相较于气溶胶的影响更为显著,证实了20世纪70年代末人类活动对中国东部夏季降水年代际转折的影响。 相似文献
14.
利用NCEP/NCAR （National Centers for Environmental Prediction/National Center for Atmospheric Research）2001-2010年再分析资料,检验了全球气候系统模式CESM中大气模块CAM （Community Atmosphere Model）对亚洲夏季风和大气热源的模拟能力。结果显示,模式可以再现亚洲夏季风和大气热源的主要特征。通过敏感试验探讨人为气溶胶影响亚洲夏季风的机理,分析、讨论了气溶胶引起的非均匀加热的变化对辐散风和无辐散风强度的影响,在机理上解释了亚洲夏季风减弱的原因。结果表明,人为气溶胶浓度的升高使东亚夏季风强度在中国东南地区、中南半岛北部和印度半岛北部减弱。而中国东南部季风的减弱促使中国内陆降水减少,沿海降水增多。进一步分析人为气溶胶浓度升高的作用发现,其改变了大气热源的分布,造成阿拉伯海、孟加拉湾和中国南海大气热源增强,中国东部地区和中南半岛大气热源减弱,其中气溶胶通过影响凝结潜热来改变大气热源,主要是对对流过程的影响。此外,大气热源分布的变化改变了季风区的热力结构,使中国东南地区、中南半岛北部的加热减弱,从而减少了全位能的产生,使得全位能向辐散风的转换减小,辐散风减弱;同时,中国东南部、中南半岛北部季风由于辐散风向无辐散风转换的减弱,无辐散风减弱,最终导致了夏季风强度的减弱。而且,人为气溶胶对亚洲夏季风的影响主要通过大气热力和动力过程的响应产生作用。 相似文献
15.
The East Asian summer monsoon (EASM) circulation and summer rainfall over East China have experienced large decadal changes
during the latter half of the 20th century. To investigate the potential causes behind these changes, a series of simulations
using the national center for atmospheric research (NCAR) community atmospheric model version 3 (CAM3) and the geophysical
fluid dynamics laboratory (GFDL) atmospheric model version 2.1 (AM2.1) are analyzed. These simulations are forced separately
with different historical forcing, namely tropical sea surface temperature (SSTs), global SSTs, greenhouse gases plus aerosols,
and a combination of global SSTs and greenhouse gases plus aerosols. This study focuses on the relative roles of these individual
forcings in causing the observed monsoon and rainfall changes over East Asia during 1950–2000. The simulations from both models
show that the SST forcing, primarily from the Tropics, is able to induce most of the observed weakening of the EASM circulation,
while the greenhouse gas plus (direct) aerosol forcing increases the land-sea thermal contrast and thus enhances the EASM
circulation. The results suggest that the recent warming in the Tropics, especially the warming associated with the tropical
interdecadal variability centered over the central and eastern Pacific, is a primary cause for the weakening of the EASM since
the late 1970s. However, a realistic simulation of the relatively small-scale rainfall change pattern over East China remains
a challenge for the global models. 相似文献
16.
基于气温和降水观测资料以及美国国家环境预报中心/国家大气研究中心（NCEP/NCAR）大气再分析资料,系统评估了大样本初始化十年际预测试验（CESM-DPLE）对1959—2016年东亚夏季气候预测的能力。结果表明,CESM-DPLE能较好地模拟东亚夏季气候以及相关主要大气环流系统的基本态特征,在年际尺度上对东亚气温有很高的预测技巧但对降水几乎没有预测能力。CESM-DPLE再现了北大西洋多年代际振荡（AMO）经由激发遥相关波列所引起的中高纬度大气环流、东亚夏季风和气候的异常。20世纪90年代末之后,北大西洋多年代际振荡由冷位相转为暖位相,遥相关波列位相调整,东亚受异常低压控制,东亚夏季风偏强,夏季气温偏高、降水偏多。总体上,尽管还存在着不足,但CESM-DPLE对东亚夏季温度年际变化以及与20世纪90年代末北大西洋多年代际振荡位相转变相联的东亚夏季气候年代际变化具备一定的预测能力,是目前研究和预测东亚气候变化的一套较好试验数据。 相似文献
17.
A unified chemistry-aerosol-climate model is applied in this work to compare climate responses to chang- ing concentrations of long-lived greenhouse gases(GHGs,CO2,CH4,N2O),tropospheric O3,and aerosols during the years 1951–2000.Concentrations of sulfate,nitrate,primary organic carbon(POA),secondary organic carbon(SOA),black carbon(BC)aerosols,and tropospheric O3 for the years 1950 and 2000 are obtained a priori by coupled chemistry-aerosol-GCM simulations,and then monthly concentrations are in- terpolated ... 相似文献
18.
全球海气耦合模式对中国区域年代际气候变化预测能力的评估 总被引：4，自引：1，他引：3
利用4个海气耦合模式对1960～2005年的多年代际回报结果,评估模式对中国区域年代际气候变化(温度和降水)的预测潜力,并初步给出2005～2015年的气候预测结果。与CMIP3多模式集合1960～2000年结果以及观测实况比较的结果表明:融入观测资料进行同化的年代际气候预测模式,对中国区域温度和降水的模拟能力总体好于CMIP3模式。年代际气候预测模式对温度气候场的模拟仍以"冷偏差"为主,但较之CMIP3模式已有显著改进,中国区域平均的冷偏差减少1.3°C;对降水气候场的模拟仍以"湿偏差"为主,但在华南沿海和西北内陆降水的模拟能力优于CMIP3模式,中国区域平均的湿偏差降低了20%。年代际模式和CMIP3模式都能较好地模拟出中国区域尤其是北方20世纪后期的增暖信号;但CMIP3模式对20世纪后期中国东部降水的旱涝结构演变的模拟与观测相反;而年代际气候预测模式未能再现华北偏旱的变化,但能成功地模拟江淮流域和华南沿海的旱涝演变。2005～2015年的10年预测表明中国区域将继续增暖0.3～0.7°C,且增温幅度北方大于南方,增幅中心位于西北内陆和青藏高原;而降水的变化趋势不显著,黄淮地区、西北内陆和青藏高原的降水略有增加,而西南地区降水将减少。但需要指出的是,这种预测的不确定性是相当大的。 相似文献