东亚夏季风降水和环流数值模拟对不同对流参数化方案的敏感性

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.     

Simulation of East Asian Summer Monsoon by Using an Improved AGCM

The IAP 2-L AGCM is modified by introducing a set of climatological surface albedo data into the model for substituting the model’s original surface albedo parameterization. The comparison between the observations and the simulation results by the modified model shows that the general features of the East Asian summer monsoon can be well reproduced by the modified IAP 2-L AGCM. Especially for the simulation of monsoon precipitation, the modi-fied model can well reproduce not only the monthly mean features of the summer monsoon rainfall over East Asia, but also the stepwise advance and retreat of the East Asian summer monsoon rainbelt. Analysis results demonstrate that the good simulation of the monsoon rainfall is closely related to the reasonable simulation of the large scale gen-eral circulation over East Asian region, such as the western Pacific subtropical high, Asian monsoon low and the low level flows. The good performance of the modified model in the rainfall simulation shows its great potential to serve as a useful tool for the prediction of summer drought / flood events over East Asia.     

East Asian summer monsoon simulation by a 20-km mesh AGCM

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.     

Multi-year simulation of the East Asian Monsoon and Precipitation in China using a Regional Climate Model and Evaluation

1. Introduction As an important way to study the global climate change, because of its low resolution, GCM (general circulation model) shows obvious deficiency and uncer- tainty in capturing some regional features when used in the regional climate study, and the uncertainty is even serious in regional climate simulation over East Asia (Ding et al., 2000; Zhao and Luo, 1998; Qian et al., 1999). The high-resolution regional climate model (RegCM) developed in the 1980s can provide better simu…     

东亚夏季风指数的年际变化与东亚大气环流

文中从夏季东亚热带、副热带环流系统特点出发 ,定义了能较好表征东亚夏季风环流年际变化的特征指数 ,并分析了东亚夏季风指数的年际变化与东亚大气环流及夏季中国东部降水的关系。文中定义的东亚夏季风指数既反映了夏季东亚大气环流风场的变化特征 ,也较好地反映了夏季中国东部降水的年际变化特征。此外 ,还探讨了东亚夏季风指数变化的先兆信号     

ECHAM4/OPYC3海气耦合模式对东亚季风年循环及其未来变化的模拟

德国马普研究所海气耦合摸式ECHAM4/OPYC3对东亚地区2 m温度年循环的模拟尽管有一些偏差,但还是相当成功的.其模拟的东亚夏季风偏弱,而冬季风偏强,此偏差可能与2 m温度以及西太平洋副热带高压模拟偏差有关.该模式模拟的东亚季风区夏季降水量偏弱,这与上述夏季风环流的模拟结果是一致的.该模式较好地抓住了华北地区经向环流和降水量的年循环特征.利用最新的温室气体和SO2排放方案,即政府间气候变化委员会(IPCC)排放方案特别报告(SRES)的A2和B2方案,通过该模式111年的积分结果讨论了东亚季风气候在21世纪后30年中的变化,其主要结果为:全球变暖导致夏季海陆温差增大和冬季海陆温差减弱,进而使东亚季风环流在夏季加强,冬季减弱.长江流域和华北地区的夏季降水量显著增强,而后者的增强更为显著,使得东亚季风区的夏季多雨区向北延伸;东亚季风区9月份的降水量在两个方案中都显著增加,说明在全球变暖条件下东亚季风区的多雨季节将延迟一个月.     

Sensitivity Study of the South China Sea Summer Monsoon in 1998 to Different Cumulus Parameterization Schemes

In this study, the improved high-resolution regional climate model of the China National Climate Center （RegCM_NCC） is used to examine the sensitivity of the simulated circulation and rainfall during the South China Sea summer monsoon （SCSSM） period during 1998 in an effort to compare to other cumulus param- eterization schemes. The investigation has indicated that the model is capable of simulating the seasonal march of the SCSSM and that the results were very sensitive to the choice of cumulus parameterization schemes. It seems that the Kuo cumulus parameterization scheme simulates the process of the SCSSM onset reasonably well, which can reproduce the onset timing and dramatic changes before and after the onset, especially the upper- and lower-level wind-fields. However, there are still some discrepancies between the simulations and observations. For example, the model can not completely simulate the intensity of the rainfall or the location of the western Pacific subtropical high as well as the feature of the rapid northward propagation of seasonal rain belt.     

INTERANNUAL VARIATION OF INDEX OF EAST ASIAN LAND-SEA THERMAL DIFFERENCE AND ITS RELATION TO MONSOON CIRCULATION AND RAINFALL OVER CHINA*

This paper proposes an index of land-sea thermal difference(ILSTD)that describes its zonal and meridional strength responsible for East Asian monsoon circulation to study its relation to the East Asian monsoon circulation and the summer rainfall over China on an interannual basis.Results are as follows:(1)ILSTD can be used to measure the strength of East Asian summer monsoon in such a way that the strong(weak)ILSTD years are associated with strong(weak)summer monsoon circulation.(2)The index also reflects well summer rainfall anomaly over the eastern part of China.In the strong index years,rain belt is mainly located over the northern China,and serious drought emerges in the Jianghuai valleys and mid-lower reaches of the Changjiang River,along with increase of rainfall in North and South China,but in the weak years it is contrary.(3)Besides,the index has obvious QBO and quasi 4-year oscillations,but the periods and amplitudes have significant changes on an interdecadal basis.     

INTERANNUAL VARIATION OF INDEX OF EAST ASIAN LAND-SEA THERMAL DIFFERENCE AND ITS RELATION TO MONSOON CIRCULATION AND RAINFALL OVER CHINA

This paper proposes an index of land-sea thermal difference(ILSTD)that describes its zonal andmeridional strength responsible for East Asian monsoon circulation to study its relation to the EastAsian monsoon circulation and the summer rainfall over China on an interannual basis.Results are asfollows:(1)ILSTD can be used to measure the strength of East Asian summer monsoon in such away that the strong(weak)ILSTD years are associated with strong(weak)summer monsooncirculation.(2)The index also reflects well summer rainfall anomaly over the eastern part of China.In the strong index years,rain belt is mainly located over the northern China,and serious droughtemerges in the Jianghuai valleys and mid-lower reaches of the Changjiang River,along with increaseof rainfall in North and South China,but in the weak years it is contrary.(3)Besides,the index hasobvious QBO and quasi 4-year oscillations,but the periods and amplitudes have significant changes onan interdecadal basis.     

Role of the cloud adjustment time scale in simulation of the interannual variability of Indian summer monsoon

The simulation of precipitation in a general circulation model relying on relaxed mass flux cumulus parameterization scheme is sensitive to cloud adjustment time scale (CATS). In this study, the frequency of the dominant intra-seasonal mode and interannual variability of Indian summer monsoon rainfall (ISMR) simulated by an atmospheric general circulation model is shown to be sensitive to the CATS. It has been shown that a longer CATS of about 5 h simulates the spatial distribution of the ISMR better. El Niño Southern Oscillation–ISMR relationship is also sensitive to CATS. The equatorial Indian Ocean rainfall and ISMR coupling is sensitive to CATS. Our study suggests that a careful choice of CATS is necessary for adequate simulation of spatial pattern as well as interannual variation of Indian summer monsoon precipitation.     

An Index Measuring the Interannual Variation of the East Asian Summer Monsoon ——The EAP Index

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.     

Spatial variability of Holocene changes in the annual precipitation pattern: a model-data synthesis for the Asian monsoon region

This study provides a detailed analysis of the mid-Holocene to present-day precipitation change in the Asian monsoon region. We compare for the first time results of high resolution climate model simulations with a standardised set of mid-Holocene moisture reconstructions. Changes in the simulated summer monsoon characteristics (onset, withdrawal, length and associated rainfall) and the mechanisms causing the Holocene precipitation changes are investigated. According to the model, most parts of the Indian subcontinent received more precipitation (up to 5 mm/day) at mid-Holocene than at present-day. This is related to a stronger Indian summer monsoon accompanied by an intensified vertically integrated moisture flux convergence. The East Asian monsoon region exhibits local inhomogeneities in the simulated annual precipitation signal. The sign of this signal depends on the balance of decreased pre-monsoon and increased monsoon precipitation at mid-Holocene compared to present-day. Hence, rainfall changes in the East Asian monsoon domain are not solely associated with modifications in the summer monsoon circulation but also depend on changes in the mid-latitudinal westerly wind system that dominates the circulation during the pre-monsoon season. The proxy-based climate reconstructions confirm the regional dissimilarities in the annual precipitation signal and agree well with the model results. Our results highlight the importance of including the pre-monsoon season in climate studies of the Asian monsoon system and point out the complex response of this system to the Holocene insolation forcing. The comparison with a coarse climate model simulation reveals that this complex response can only be resolved in high resolution simulations.     

南海夏季风爆发的数值模拟

利用高分辨率的区域气候模式 (RegCM_NCC) 对南海夏季风爆发进行模拟研究。研究表明:该模式对积云对流参数化方案的选择十分敏感, 其中以Kuo积云参数化方案为最好, 可以比较成功地模拟出南海夏季风的爆发时间、爆发前后高、低层风场的剧烈变化以及季风与季风雨带的向北推进。然而该方案对于雨量和副热带高压位置的模拟, 与观测相比尚存在一定的偏差, 主要表现为副热带高压位置模拟偏北、偏东; 南海地区的降水量模拟偏少、降水范围偏小。此外, 采用4种参数化方案 (Kuo, Grell, MFS, Betts-Miller) 集成的结果在某种程度上要优于单个方案的结果, 这种改善主要体现在对南海地区季风爆发后降水的模拟上。     

Intermodel Diversity in the Zonal Location of the Climatological East Asian Westerly Jet Core in Summer and Association with Rainfall over East Asia in CMIP5 Models

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.     

Impacts of Cumulus Convective Parameterization Schemes on Summer Monsoon Precipitation Simulation over China

By using the Betts-Miller-Janjic, Grell-Devenyi, and Kain-Fritsch cumulus convective parameterization schemes in theWeather Research and Forecasting (WRF) model, long time simulations from 2000 to 2009 are conducted to investigate the impacts of different cumulus convective parameterization schemes on summer monsoon precipitation simulation over China. The results show that all the schemes have the capability to reasonably reproduce the spatial and temporal distributions of summer monsoon precipitation and the corresponding background circulation. The observed north-south shift of monsoon rain belt is also well simulated by the three schemes. Detailed comparison indicates that the Grell-Devenyi scheme gives a better performance than the others. Deficiency in simulated water vapor transport is one possible reason for the precipitation simulation bias.     

El Nio和La Nia冬季增强型和减弱型及其对中国夏季旱涝的影响

根据 El Nino和 La Nina发生以后冬季赤道东太平洋海温距平的月际差定义了 El Nino和 La Nina冬季增强型和冬季减弱型 ,讨论了 El Nino和 La Nina冬季增强型和减弱型冬、春、夏季大气环流、东亚季风及我国夏季降水和旱涝分布的特征 .我国夏季降水和旱涝有明显差异的四种不同分布型可能与冬季所处 ENSO循环的不同阶段以及大气环流和东亚季风对它的不同响应有关 .提出了从 El Nino和 La Nina冬季不同型→大气环流和东亚季风→我国夏季降水和旱涝分布型的物理统计概念模型 .     

NUMERICAL SIMULATION OF THE INFLUENCE OF INDIAN OCEAN DIPOLE ON CLIMATIC VARIATIONS OVER EAST ASIAN MONSOON REGION DURING EQUATORIAL EAST PACIFIC OCEAN SSTA

1 INTRODUCTION In the recent years, more and more researches have shown that the effect of Tropical Ocean is very evident in the process of ocean-air interaction; Sea-Surface Temperature Anomaly (SSTA) takes on global configuration and SSTA in different areas are interrelated and also have their respective characteristics. The SSTA over Indian Ocean and Pacific Ocean are interrelated. WU et al.[1] and MENG et al.[2] indicated that the evident positive correlation of inter-annual…     

青藏高原积雪与亚洲季风环流年代际变化的关系

利用高原测站的月平均雪深资料和NCEP／NCAR再分析资料，分析了20世纪70年代末以来，青藏高原积雪的显著增多与亚洲季风环流转变的联系。研究表明，高原南侧冬春季西风的增强及西风扰动的活跃是造成青藏高原冬春积雪显著增多的主要原因，高原积雪的增多与亚洲夏季风的减弱均是亚洲季风环流转变的结果；20世纪70年代末以来，夏季华东降水的增多、华南降水的减少及华北的干旱化与青藏高原冬春积雪增多及东亚夏季风的减弱是基本同步的，高原冬春积雪与华东夏季降水的正相关、与华北及华南夏季降水的负相关主要是建立在年代际时间尺度上，因此，高原积雪与我国夏季降水关系的研究应以亚洲季风环流的年代际变化为背景。     

El Ni?o和La Ni?a冬季增强型和减弱型及其对中国夏季旱涝的影响

根据El Ni?o和La Ni?a发生以后冬季赤道东太平洋海温距平的月际差定义了El Ni?o和La Ni?a冬季增强型和冬季减弱型, 讨论了El Ni?o和La Ni?a冬季增强型和减弱型冬、春、夏季大气环流、东亚季风及我国夏季降水和旱涝分布的特征.我国夏季降水和旱涝有明显差异的四种不同分布型可能与冬季所处ENSO循环的不同阶段以及大气环流和东亚季风对它的不同响应有关.提出了从El Ni?o和La Ni?a冬季不同型→大气环流和东亚季风→我国夏季降水和旱涝分布型的物理统计概念模型.