首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到18条相似文献，搜索用时 125 毫秒
1.
Response of the East Asian summer monsoon(EASM) rainfall to external forcing(insolation,volcanic aerosol,and greenhouse gases) is investigated by analysis of a millennium simulation with the coupled climate model ECHO-G.The model reproduces reasonably realistic present-day EASM climatology.The simulated precipitation variation in East Asia over the last millennium compares favorably with the observed and proxy data.It is found that the features and sensitivity of the forced response depend on latitude.On...  相似文献   

2.
Using the monthly mean NCEP/NCAR reanalysis data and the monthly rainfall observations at 160 rain gauge stations of China during 1961 1999, and based on major characteristics of the atmospheric circulation over East Asia and the western Pacific, a simple index for the East Asian subtropical summer monsoon （EASSM） is defined. The relationship between this index and summer rainfall in China and associated circulation features are examined. A comparison is made between this index and other monsoon indices. The results indicate that the index defined herein is reflective of variations of both the thermal low pressure centered in Siberia and the subtropical ridge over the western Pacific. It epitomizes the intensity of the EASSM and the variability of summer rainfall along the Yangtze River. Analysis shows that the Siberian low has a greater effect on the rainfall than the subtropical ridge, suggesting that the summer rainfall variability over the eastern parts of China is to a large extent affected by anomalies of the atmospheric circulation and cold air development in the midlatitudes. Taking into account of the effects of both the Siberian low and the subtropical ridge can better capture the summer rainfall anomalies of China. The index exhibits interannual and decadal variabilities, with high-index values occurring mainly in the 1960s and 1970s and low-index values in the 1980s and 1990s. When the EASSM index is low, the Siberian low and the subtropical ridge are weaker, and northerly wind anomalies appear at low levels over the midlatitudes and subtropics of East Asia, whereas southwesterly wind anomalies dominate in the upper troposphere over the tropics and subtropics of Asia and the western Pacific. The northerly wind anomalies bring about frequent cold air disturbances from the midlatitudes of East Asia, strengthening the convergence and ascending motions along the Meiyu front, and result in an increase of summer rainfall over the Yangtze River.  相似文献   

3.
The seasonal variations of the Asian monsoon were explored by applying the atmospheric general circulation model R42L9 that was developed recently at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences (LASG/IAP/CAS). The 20-yr (1979-1998) simulation was done using the prescribed 20-yr monthly SST and sea-ice data as required by Atmospheric Model Intercomparison Project (AMIP)Ⅱ in the model. The monthly precipitation and monsoon circulations were analyzed and compared with the observations to validate the model‘s performance in simulating the climatological mean and seasonal variations of the Asian monsoon. The results show that the model can capture the main features of the spatial distribution and the temporal evolution of precipitation in the Indian and East Asian monsoon areas. The model also reproduced the basic patterns of monsoon circulation. However, some biases exis tin this model. The simulation of the heating over the Tibetan Plateau in summer was too strong. The overestimated heating caused a stronger East Asian monsoon and a weaker Indian monsoon than the observations. In the circulation fields, the South Asia high was stronger and located over the Tibetan Plateau. The western Pacific subtropical high was extended westward, which is in accordance with the observational results when the heating over the Tibetan Plateau is stronger. Consequently, the simulated rainfall around this area and in northwest China was heavier than in observations, but in the Indian monsoon area and west Pacific the rainfall was somewhat deficient.  相似文献   

4.
Based on the EAP (East Asia/Pacific) teleconnection in the summer circulation anomalies over ther Northern Hemisphere, an index measuring the strength of the East Asian summer monsoon, i.e., the so-called EAP index, is defined in this paper. From the analyses of observed data, it is clearly shown that the EAP index defined in this study can well describe the interannual variability of summer rainfall and surface air temperature in East Asia, especially in the Yangtze River valley and the Huaihe River valley, Korea,and Japan. Moreover, this index can also reflect the interannual variability of the East Asian summer monsoon system including the monsoon horizontal circulation and the vertical-meridional circulation cell over East Asia. From the composite analyses of climate and monsoon circulation anomalies for high EAP index and for low EAP index, respectively, it is well demonstrated that the EAP index proposed in this study can well measure the strength of the East Asian summer monsoon.  相似文献   

5.
The role of various mountains in the Asian monsoon system is investigated by AGCM simulations with different mountains.The comparison of the simulation with Asian mountains(MAsia run)with the simulation without mountains(NM run)reveals that the presence of the Asian mountains results in a stronger South Asian summer monsoon(SASM),characterized by enhanced lower-tropospheric westerly winds,uppertropospheric easterly winds,and stronger water vapor convergence.In East Asia,the southerly winds and water vapor convergence are significantly strengthened in association with the intensified zonal pressure gradient between the East Asian continent and the Pacific Ocean.Both the dynamical and thermodynamic forcing of the Tibetan Plateau play important role in strengthening the Asian summer monsoon.In winter,the presence of Asian mountains significantly strengthens the continental high,which leads to a stronger Asian winter monsoon.The presence of African-Arabian mountains helps to intensify the exchange of mass between the Southern Hemisphere and Northern Hemisphere by strengthening the cross equatorial flows in the lower and upper troposphere over East Africa. Asian mountains also play a crucial role in the seasonal evolution of Asian monsoons.In comparison with the NM run,the earlier onset and later withdrawal of lower-tropospheric westerly winds can be found over South Asia in the MAsia run,indicating a longer SASM period.The African-Arabian mountains also moderately contribute to the seasonal variation of the South Asian monsoon.In East Asia,the clear southto-north march of the southerly winds and subtropical rainfall starts to occur in early summer when the effects of Asian mountains are considered.  相似文献   

6.
The East Asian westerly jet(EAJ), an important midlatitude circulation of the East Asian summer monsoon system,plays a crucial role in affecting summer rainfall over East Asia. The multimodel ensemble of current coupled models can generally capture the intensity and location of the climatological summer EAJ. However, individual models still exhibit large discrepancies. This study investigates the intermodel diversity in the longitudinal location of the simulated summer EAJ climatology in the present-day climate and its implications for rainfall over East Asia based on 20 CMIP5 models. The results show that the zonal location of the simulated EAJ core is located over either the midlatitude Asian continent or the western North Pacific(WNP) in different models. The zonal shift of the EAJ core depicts a major intermodel diversity of the simulated EAJ climatology. The westward retreat of the EAJ core is related to a warmer mid–upper tropospheric temperature in the midlatitudes, with a southwest–northeast tilt extending from Southwest Asia to Northeast Asia and the northern North Pacific, induced partially by the simulated stronger rainfall climatology over South Asia. The zonal shift of the EAJ core has some implications for the summer rainfall climatology, with stronger rainfall over the East Asian continent and weaker rainfall over the subtropical WNP in relation to the westward-located EAJ core.  相似文献   

7.
A 5-level spectral AGCM (ImPKU-5LAGCM) is used to examine the sensitivity of the simulated results of the summer monsoon rainfall and circulation in East Asia to different cumulus parameterization schemes in the climatological-mean case and in the cases of weak and strong Asian summer monsoons,respectively. The results simulated with the Arakawa-Schubert＇s(hereafter A-S＇s), Kuo＇s and Manabe＇s cumulus parameterization schemes show that these simulated distributions of the summer monsoon rainfall and circulation in East Asia depend strongly on the cumulus parameterization schemes either in the climatological-mean case or in the cases of weak and strong Asian summer monsoons. From the simulated results, it might be shown that the Kuo scheme appears to be more suitable for the simulation of the summer monsoon rainfall and circulation in East Asia than the A-S scheme or the Manabe scheme, although the A-S scheme is somewhat better in the simulations of the tropical rainfall. This might be due to that the Kuo＇s cumulus parameterization scheme is able to reflect well the characteristics of rainfall cloud system in the East Asian summer monsoon region, where the rainfall system used to be a mixing of cumulus and stratus.  相似文献   

8.
In this study, the relationship between the subsystems of Asian summer monsoon is analyzed using U.S. National Centers for Environmental Protection/National Center for Atmospheric Research reanalysis and Climate Prediction Center Merged Analysis of Precipitation monthly mean precipitation data. The results showed that there is significant correlation between the subsystems of Asian summer monsoon. The changes of intensity over the same period show that weak large-scale Asian monsoon, Southeast Asia monsoon and South Asian monsoon are associated with strong East Asian monsoon and decreasing rainfall in related areas. And when the large-scale Asian monsoon is strong, Southeast Asia and South Asia monsoons will be strong and precipitation will increase. While the Southeast Asia monsoon is strong, the South Asia monsoon is weak and the rainfall of South Asia is decreasing, and vice versa. The various subsystems are significantly correlated for all periods of intensity changes.  相似文献   

9.
Recent advances in dynamical climate prediction at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS) during the last five years have been briefly described in this paper. Firstly,the second generation of the IAP dynamical climate prediction system (IAP DCP-II) has been described,and two sets of hindcast experiments of the summer rainfall anomalies over China for the periods of 1980-1994 with different versions of the IAP AGCM have been conducted. The comparison results show that the predictive skill of summer rainfall anomalies over China is improved with the improved IAP AGCM in which the surface albedo parameterization is modified. Furthermore, IAP DCP-II has been applied to the real-time prediction of summer rainfall anomalies over China since 1998, and the verification results show that IAP DCP-II can quite well capture the large scale patterns of the summer flood/drought situations over China during the last five years (1998-2002). Meanwhile, an investigation has demonstrated the importance of the atmospheric initial conditions on the seasonal climate prediction, along with studies on the influences from surface boundary conditions (e.g., land surface characteristics, sea surface temperature).Certain conclusions have been reached, such as, the initial atmospheric anomalies in spring may play an important role in the summer climate anomalies, and soil moisture anomalies in spring can also have a significant impact on the summer climate anomalies over East Asia. Finally, several practical techniques(e.g., ensemble technique, correction method, etc.), which lead to the increase of the prediction skill for summer rainfall anomalies over China, have also been illustrated. The paper concludes with a list of criticalre quirements needed for the further improvement of dynamical seasonal climate prediction.  相似文献   

10.
In this paper, a 5-level spectral AGCM is used to examine the sensitivity of simulated East Asian summer mon-soon circulation and rainfall to cumulus parameterization schemes. From the simulated results of East Asian mon-soon circulations and rainfalls during the summers of 1987 and 1995, it is shown that the Kuo’s convective parameterization scheme is more suitable for the numerical simulation of East Asian summer monsoon rainfall and circulation. This may be due to that the cumulus in the rainfall system is not strong in the East Asian monsoon region.  相似文献   

11.
Comparative tests and analyses on monsoon and regional precipitation   总被引：1，自引：0，他引：1  
Summary Due to the strong variation of the Asian monsoon, many countries in Asia often suffer from serious natural disasters. Droughts and floods appear in East China frequently related to the large anomalies of the two branches of East Asian monsoon. Based on rainfall data recorded by 336 Chinese stations in the 1980s, two distinctly opposite rainfall types over East China in summer (JJA) are discovered. Correspondly, 850 hPa anomalous wind fields in the Eastern Hemisphere are also possessed by two types of converse patterns in spring (MAM) and summer (JJA). The onset time and intensity of the Somali jet and the two branches of Southeast and Indian monsoon are quite different. Furthermore, in the 500 hPa geopotential height anomaly fields in spring and summer, the variations of the previous general atmospheric circulation (in spring) are closely correlated to the two kinds of conversely distributed rainfall in summer. These two types of rainfall are also related to two types of conversely distributed sea surface temperature anomaly (SSTA) in the equatorial Pacific and Indian Oceans. To investigate model capabilities refelecting the above observed features, eight numerical experiments are carried out using the IAP 2-L AGCM, with observed monthly mean global SSTs as external forcing and observed atmospheric data on February 15 as initial conditions. The simulated distributions of rainfall anomalies over East China in summer are in good accordance with observations. With conversely distributed SSTAs in the equatorial Pacific, the simulated 850 hPa anomalous wind fields and the 500 hPa geopotential height anomalies are also conversely distributed, and are closely related to the two types of simulated rainfall anomalies over East China. The cross equatorial wind varies in strength, space and time. The simulated distributions of anomalous 500 hPa geopotential height in spring and the anomalous wind at 850 hPa in spring and summer are quite similar to observations.With 10 Figures  相似文献   

12.
East Asian summer monsoon simulation by a 20-km mesh AGCM   总被引：1，自引：0，他引：1  
East Asian summer monsoon climate simulated by a global 20-km mesh atmospheric general circulation model (AGCM) forced by the global sea surface temperature during the period 1979–1998 is investigated. In comparison with a lower resolution (180-km mesh) model experiment, it is revealed that the 20-km mesh AGCM shows the superiority in simulating orographic rainfall not only its location but also its amount. The Baiu frontal structure is also better simulated in the higher resolution model, which leads to stronger Baiu rainfall. The 20-km model also shows more intense extremes in precipitation. Interannual variability of June–August mean precipitation and seasonal march of the monsoon rain band are also investigated. This paper is a contribution to the AMIP-CMIP Diagnostic Sub-project on General Circulation Model Simulation of the East Asian Climate, coordinated by W.-C. Wang.  相似文献   

13.
In this paper, a 5-level spectral AGCM is used to examine the sensitivity of simulated East Asian summer monsoon circulation and rainfall to cumulus parameterization schemes. From the simulated results of East Asian monsoon circulations and rainfalls during the summers of 1987 and 1995, it is shown that the Kuo’s convective parameterization scheme is more suitable for the numerical simulation of East Asian summer monsoon rainfall and circulation. This may be due to that the cumulus in the rainfall system is not strong in the East Asian monsoon region. This paper is supported by the National Key Progranmme “96-908”.  相似文献   

14.
Simulation of East Asian Summer Monsoon with IAP CGCM   总被引：1，自引：0，他引：1  
ＳｉｍｕｌａｔｉｏｎｏｆＥａｓｔＡｓｉａｎＳｕｍｍｅｒＭｏｎｓｏｏｎｗｉｔｈＩＡＰＣＧＣＭＣｈｅｎＱｉｙｉｎｇ（陈起英），①ＹｕＹｏｎｇｑｉａｎｇ（俞永强）ａｎｄＧｕｏＹｕｆｕ（郭裕福）ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ，Ｃｈ...  相似文献   

15.
ＴｈｅＥｆｅｃｔｏｆＨｅａｔｉｎｇＡｎｏｍａｌｙｏｎｔｈｅＡｓｉａｎＣｉｒｃｕｌａｔｉｏｎ－ＡＧＣＭＥｘｐｅｒｉｍｅｎｔ①ＷａｎｇＨｕｉｊｕｎ（王会军）ＬＡＳＧ，ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙ...  相似文献   

16.
A numerical experiment was done by using the IAP 9-Level AGCM to study the effects of radiation anomaly over East Asia on the Asian general circulation. The results show that the changes of Asian summer general circula-tion are remarkable in the Indian and China southwest monsoon, precipitation in India and the Yellow River and Huaihe River valley in China and area around the north Japan, the easterly anomaly of low-level zonal wind in the tropical Pacific and so on.  相似文献   

17.
Coupled Model Inter-comparison Project Phase 5 (CMIP5) model outputs of the South and East Asian summer monsoon variability and their tele-connections are investigated using historical simulations (1861-2005) and future projections under the RCP4.5 scenario (2006-2100). Detailed analyses are performed using nine models having better representation of the recent monsoon teleconnections for the interactive Asian monsoon sub-systems. However, these models underestimate rainfall mainly over South Asia and Korea-Japan sector, the regions of heavy rainfall, along with a bias in location of rainfall maxima. Indeed, the simulation biases, underestimations of monsoon variability and teleconnections suggest further improvements for better representation of Asian monsoon in the climate models. Interestingly, the performance of Australian Community Climate and Earth System Simulator version 1.0 (ACCESS1.0) in simulating the annual cycle, spatial pattern of rainfall and multi-decadal variations of summer monsoon rainfall over South and East Asia appears to more realistic. In spite of large spread among the CMIP5 models, historical simulations as well as future projections of summer monsoon rainfall indicate multi-decadal variability. These rainfall variations, displaying certain epochs of more rainfall over South Asia than over East Asia and vice versa, suggest an oscillatory behaviour. Teleconnections between South and East Asian monsoon rainfall also exhibit a multi-decadal variation with alternate epochs of strengthening and weakening relationship. Furthermore, large-scale circulation features such as South Asian monsoon trough and north Pacific subtropical high depict zonal oscillatory behaviour with east-west-east shifts. Periods with eastward or westward extension of the Mascarene High, intensification and expansion of the upper tropospheric South Asian High are also projected by the CMIP5 models.  相似文献   

18.
ＳｉｍｕｌａｔｉｏｎｏｆｔｈｅＡｓｉａｎＭｏｎｓｏｏｎｂｙＩＡＰＡＧＣＭＣｏｕｐｌｅｄｗｉｔｈａｎＡｄｖａｎｃｅｄＬａｎｄＳｕｒｆａｃｅＭｏｄｅｌ（ＩＡＰ９４）ＺｅｎｇＱｉｎｇｃｕｎ（曾庆存）,ＤａｉＹｏｎｇｊｉｕ（戴永久）ａｎｄＸｕｅＦｅｎｇ（薛峰...  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号