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…     

The Role of Land-sea Distribution and Orography in the Asian Monsoon. Part Ⅱ:Orography

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.     

The Role of Land-sea Distribution and Orography in the Asian Monsoon. Part II： Orography

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, upper-tropospheric 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 south-to-north march of the southerly winds and subtropical rainfall starts to occur in early summer when the effects of Asian mountains are considered.     

The Influence of ENSO on the Summer Climate Change in China and Its Mechanism

The influence of ENSO on the summer climate change in China and its mechanism from the observed data is discussed. It is discovered that in the developing stage of ENSO, the SST in the western tropical Pacific is colder in summer, the convective activities may be weak around the South China Sea and the Philippines. As a consequence, the subtropical high shifted southward. Therefore, a drought may be caused in the Indo-China peninsula and in the South China. Moreover, in midsummer the subtropical high is weak over the Yangtze River valley and Huaihe River valley, and the flood may be caused in the area from the Yangtze River valley to Huaihe River valley. On the contrary, in the decaying stage of ENSO. the convective activities may be strong around the Philippines, and the subtropical high shifted northward, a drought may be caused in the Yangtze River valley and Huaihe River valley.     

The Role of Land–sea Distribution and Orography in the Asian Monsoon. Part I： Land–sea Distribution

A number of AGCM simulations were performed by including various land--sea distributions (LSDs), such as meridional LSDs, zonal LSDs, tropical large-scale LSDs, and subcontinental-scale LSDs, to identify their effects on the Asian monsoon. In seven meridional LSD experiments with the continent/ocean located to the north/south of a certain latitude, the LSDs remain identical except the southern coastline is varied from 40^o to 4^oN in intervals of 5.6^o. In the experiments with the coastline located to the north of 21^oN, no monsoon can be found in the subtropical zone. In contrast, a summer monsoon is simulated when the continent extends to the south of 21^oN. Meanwhile, the earlier onset and stronger intensity of the tropical summer monsoon are simulated with the southward extension of the tropical continent. The effects of zonal LSDs were investigated by including the Pacific and Atlantic Ocean into the model based on the meridional LSD run with the coastline located at 21^oN. The results indicate that the presence of a mid-latitude zonal LSD induces a strong zonal pressure gradient between the continent and ocean, which in turn results in the formation of an East Asian subtropical monsoon. The comparison of simulations with and without the Indian Peninsula and Indo-China Peninsula reveals that the presence of two peninsulas remarkably strengthens the southwesterly winds over South Asia due to the tropical asymmetric heating between the tropical land and sea. The tropical zonal LSD plays a crucial role in the formation of cumulus convection.     

The Role of Land–sea Distribution and Orography in the Asian Monsoon. Part I: Land–sea Distribution

A number of AGCM simulations were performed by including various land–sea distributions (LSDs), such as meridional LSDs, zonal LSDs, tropical large-scale LSDs, and subcontinental-scale LSDs, to identify their effects on the Asian monsoon. In seven meridional LSD experiments with the continent/ocean located to the north/south of a certain latitude, the LSDs remain identical except the southern coastline is varied from 40 ° to 4 ° N in intervals of 5.6° . In the experiments with the coastline located to the n...     

Regional and Synoptic-scale Features Associated with Inactive Periods of the Summer Monsoon over South China

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The Weakening of the Asian Monsoon Circulation after the End of 1970＇s

The transition of the global atmospheric circulation in the end of 1970＇s can clearly be detected in the atmospheric temperature, wind velocity, and so on. Wavelet analysis reveals that the temporal scale of this change is larger than 20 years. Studies in this work indicate that the trend of the transition over the mid-latitude Asia is opposite to that of global average for some variables at the middle troposphere. Another finding of this research is that the African-Asian monsoon circulation is weaker and the trade wind over the tropical eastern Pacific is weaker as well after this transition. Such a signal may be found in the summer precipitation over China as well.     

A Modeling Study of Climate Change and Its Implication for Agriculture in China Part II: The Implication of Climate Change for Agriculture in China

The potential CO2-induced impacts on the geographical shifts of wheat growth zones in China were studied from seven GCMs outputs. The wheat growth regions may move northward and westward under the condition of a doubling CO2 climate. The wheat cultivation features and variety types may also assume significant changes. Climatic warming would have a positive influence in Northeast China, but high temperature stress may be produced in some regions of central and southern China. Higher mean air temperatures during wheat growth, particularly during the reproductive stages, may increase the need for earlier-maturing and more heat-tolerant cultivars.     

Recent Progress in the Impact of the Tibetan Plateau on Climate in China

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     

绿色气候基金在全球气候治理体系中的作用和展望

作为《联合国气候变化框架公约》(简称公约）和《巴黎协定》资金机制最大运营实体,绿色气候基金(GCF)不仅是发达国家兑现1000亿美元长期资金承诺的重要平台,亦是公约和《巴黎协定》目标达成的关键因素。文中系统总结了GCF在推进气候变化国际合作进程、为发展中国家应对气候变化提供资金支持、推动私营部门参与应对气候变化行动等方面的积极作用。提出在当前多边合作面临挑战的复杂背景下,GCF亦面临美国退群、缺乏有效决策机制、项目质量及秘书处能力有待提高等系列问题。文章认为,一个持续有效运营的GCF是国际社会落实《巴黎协定》实施细则的重要保障,各方应尽快凝聚政治共识,推动GCF在全球气候治理体系中继续发挥积极作用。首先,应通过引入投票权决策机制、完善政策缺口、创新业务模式等措施提升基金治理和运营效率;其次,通过尽快完成正式增资进程、拓宽资金渠道、加强剩余资金管理等方式确保充足及可持续的资金来源;最后,还应通过强化与现有气候基金的协调互补、加大与多边发展银行的合作等途径与各方资金形成合力,推动资金流向低碳和气候韧性发展领域。文章还提出,中国应在有效发挥发达国家和发展中国家桥梁作用的基础上,引导GCF投票权改革以消除政治因素对GCF长远发展的负面影响,同时通过积极争取获得下届董事席位,推进与GCF全方位合作、参与GCF正式增资进程等举措,服务生态文明建设及全球应对气候变化目标。     

The NPO/ NAO and interdecadal climate variation in China

This article discusses the interannual variation of the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO), its relationship with the interdecadal climate variation in China which is associated with the climate jump in the Northern Hemisphere in the 1960’s, using the data analyses. It is clearly shown that both the amplitudes of the NAO and NPO increase obviously in the 1960’s and the main period of the oscillations changes from 3-4 years before the 1960’s to 8-15 years after the 1960’s. Therefore, interdecadal climate variation in China or the climate jump in the 1960’s is closely related to the anomalies of the NAO and NPO.     

孟加拉湾西南季风与南海热带季风季节内振荡特征的比较

采用美国国家环境预报中心的向外长波辐射和风场资料及日本气象厅的降水资料,用30-60d滤波后的夏季风指数在孟加拉湾和南海的区域平均值分别代表孟加拉湾西南季风和南海热带季风季节内振荡,对两支季风的季节内振荡特征进行比较分析,发现孟加拉湾西南季风的季节内振荡和南海热带季风的季节内振荡在夏季风期间(5-10月)都有约3次半的波动.夏季风期间,在阿拉伯海-西太平洋纬带上,夏季风的季节内振荡有4次从阿拉伯海的东传和3次从西太平洋的西传,其中7月后东传可直达西太平洋.孟加拉湾和南海在夏季风期间都有4次季节内振荡的经向传播,但孟加拉湾在约15°N以南为季节内振荡从热带东印度洋的北传,在约15°N以北则为副热带季风季节内振荡的南传;而在南海则是4次季节内振荡从热带的北传.在以孟加拉湾西南季风季节内振荡和南海热带季风季节内振荡分别划分的6个位相中,都存在1-3位相和4-6位相中低频对流、环流形势相反的特征,这是由热带东印度洋季节内振荡的东传和北传所致.热带印度洋季节内振荡沿西南-东北向经过约14d传到孟加拉湾,激发了孟加拉湾西南季风季节内振荡的东传,经过约6d到达南海,激发了南海热带季风季节内振荡的北传,经过约25d到达华南,形成热带印度洋季节内振荡向华南的经纬向接力传播(45d).孟加拉湾西南季风季节内振荡所影响的降水主要是在20°N以南的热带雨带随低频对流的东移而东移;而南海热带季风季节内振荡所影响的降水除了这种热带雨带随低频对流的东移外,还有在20°N以北的东亚副热带地区存在雨带随南海低频对流的北移而北移.     

IPCC AR6报告解读：短寿命气候强迫因子的气候及环境效应

影响气候变化的大气成分,依据其在大气中存留的时间,分为长寿命的温室气体和短寿命的气候强迫因子（SLCFs)。考虑到SLCFs在气候变化和大气环境中的重要作用,IPCC第六次评估报告（AR6）首次有了专门针对SLCFs的章节（第六章)。本文解读IPCC报告关于SLCFs的主要结论,特别强调AR5以来的最新结论,包括：SLCFs的定义、SLCFs排放和大气含量的变化特征及其对辐射强迫和全球气候的影响、不同共享社会经济路径（SSP）情景下SLCFs对未来气候变化和空气质量可能的影响,以及COVID-19疫情期间减排对气候变化的影响。文末也讨论了结论的不确定性以及结论对我国的启示。     

中国气候预测研究与业务发展的回顾

天气预报是指一周内至两周时间尺度的气象预报,而月季及以上时间尺度的预报则属于气候预测范畴。中国的气候预测起步很早,无论在研究工作中还是在业务应用上都取得了显著成就。文中扼要回顾了这些研究和业务发展成就,重点包括:对于季风和梅雨、寒潮的早期认知和后期研究发现、早期气候预测业务发展概况、动力气候预测的早期探索、动力-统计气候预测方法的研制和应用、气候预测模式的发展以及初始化和多模式集合预测、东亚气候系统变异的全方位探索、气候预测范畴的不断拓展和气候预测研究的不断创新。也对未来气候预测研究和业务发展提出了几个重大挑战性课题,涉及不同时间尺度气候变异过程之间的相互作用、季节内至年代际气候预测、气候系统模式及初始化、动力-统计相结合的气候预测方法等方面。     

Characteristics and variations of the East Asian monsoon system and its impacts on climate disasters in China

Recent advances in studies of the structural characteristics and temporal-spatial variations of the East Asian monsoon （EAM） system and the impact of this system on severe climate disasters in China are reviewed. Previous studies have improved our understanding of the basic characteristics of horizontal and vertical structures and the annual cycle of the EAM system and the water vapor transports in the EAM region. Many studies have shown that the EAM system is a relatively independent subsystem of the Asian- Australian monsoon system, and that there exists an obvious quasi-biennial oscillation with a meridional tripole pattern distribution in the interannual variations of the EAM system. Further analyses of the basic physical processes, both internal and external, that influence the variability of the EAM system indicate that the EAM system may be viewed as an atmosphere-ocean-land coupled system, referred to the EAM climate system in this paper. Further, the paper discusses how the interaction and relationships among various components of this system can be described through the East Asia Pacific （EAP） teleconnection pattern and the teleconnection pattern of meridional upper-tropospheric wind anomalies along the westerly jet over East Asia. Such reasoning suggests that the occurrence of severe floods in the Yangtze and Hualhe River valleys and prolonged droughts in North China are linked, respectively~ to the background interannual and interdecadal variability of the EAM climate system. Besides, outstanding scientific issues related to the EAM system and its impact on climate disasters in China are also discussed.     

东亚冬季风的年代际变化及其与全球气候变化的可能联系

对近年来中外关于东亚冬季风(EAWM)年代际变化问题研究进展做了回顾和评述,主要包括以下3个方面内容:(1)东亚冬季风明显受到全球气候变化的影响,从20世纪50年代开始,中国冬季气温经历了一次冷期(从20世纪50年代延续到80年代初中期),一次暖期(从20世纪80年代初中后期延续到21世纪初)和近10-15年(约从1998年开始)出现的气候变暖趋缓期(也称气候变暖停顿期)。(2)东亚冬季风主要表现出强-弱-强3阶段的特征,即从1950年到1986/1987年,明显偏强;从1986/1987年冬季开始,东亚冬季风减弱;约2005年之后,东亚冬季风开始由弱转强。与东亚冬季风的年代际变化特征相对应,东亚冬季大气环流以及中国冬季气温和寒潮都表现出一致的年代际变化。(3)东亚冬季风的年代际变化与大气环流和太平洋海表温度(SST)的区域模态变化密切相关。当北半球环状模/北极涛动(NAM/AO)和太平洋年代际振荡(PDO)处于负(正)位相,东亚冬季风偏强(弱),中国冬季气温偏低(高)。此外,北大西洋年代尺度振荡(AMO)对东亚冬季风也有重要影响,在AMO负位相时,对应东亚冷期(强冬季风),正位相对应暖期(弱冬季风)。因而海洋的年代际变化是造成东亚冬季风气候脉动的主要自然原因,而全球气候变暖对东亚冬季风强度的减弱也有明显影响。     

亚洲急流与冬季风的关系及其对中国气候的影响

利用NCEP\NCAR逐月再分析资料和中国台站逐日观测数据,采用奇异值分解(SVD)、相关分析和合成分析等方法,研究冬季亚洲高空急流的配置与冬季风的关系及其对地面气候的影响.结果表明,青藏高原至亚洲东部沿海的副热带急流强(弱),高纬的温带急流弱(强)时,中国中、东部大范围地区气温偏低(高);中东急流强(弱),东亚副热带急流偏南(北),温带急流东南部较弱(强)时,西南气温偏低(高),东北气温偏高(低),中、东部地区冬季降水偏多(少).结合水平风场的变化,副热带地区出现西风异常弱,温带出现东风异常时,有利于东亚大槽加深并向南扩张,低层偏北风加强,东亚冬季风增强,而青藏高原反气旋环流被削弱,冷高压减弱,相应的高原季风减弱.高、低纬急流区纬向风的差异较大时,加强了急流对低层冷、暖空气交绥的引导和汇聚的作用.东亚季风指数(EAMI)与高原季风指数(PMI)在冬季多呈负相关.冬季风异常期间,若副热带急流偏强,温带急流偏弱,高纬的干冷空气受南侧急流的汇聚作用而南侵,有利于中国大部分地区降温,降水减少;反之,低纬的暖湿气流受到北侧急流引导而向北输送,导致中国大部分地区升温,降水偏多.     

Aligning climate action with the self-interest and short-term dominated priorities of decision-makers

The global and long-term nature of climate change conflicts with the self-interest and short-term dominated priorities of decision-makers. Climate change mitigation makes sense at the global level, but not at the level of the individual decision-maker. This conflict has been and remains the main obstacle to effective global cooperation and mitigation. This paper proposes a framework that aligns climate action with short-term self-interest through results-based payments to governments. Its key components are: determining an emission benchmark for each country as well as a price for carbon saving; paying countries annually for reducing emissions below their respective benchmark; a new international fund to finance these annual payments by borrowing capital from private investors; and repaying borrowings in the long-term through payments made by countries to the fund based on a pre-determined allocation mechanism. This framework would offer important benefits over an approach focused on allocating climate action or a carbon budget among countries. These include the improved prospect of reaching an effective climate agreement and delivering fast and dramatic mitigation thanks to stronger political commitment, the transformation of short-term self-interest from an obstacle into a driver of climate action, and the additional financing created. The paper also proposes a pilot scheme focusing on hydrofluorocarbon emissions with a considerably lower financing requirement. This offers the possibility of an alternative financing mechanism, and thus a faster and more straightforward implementation path. Short-term financial incentives offered to governments could turn policy action from a burden into an opportunity from their perspective unlocking a huge potential for timely mitigation.

Key policy insights

• A new international framework that offers short-term, results-based payments to governments to promote mitigation action could lead to much more effective global mitigation and international cooperation.

• The financing of such an approach could be solved through a novel financing structure, backed by the long-term commitments of participating countries and thus aligning the timeframe of the financial costs of mitigation with its climate benefits.

• The effectiveness of results-based payments and the concept behind this new approach could be proven through a pilot scheme focusing on hydrofluorocarbon emissions.

     

基于卫星观测的南海表层温度气候学特征及长期变化

利用高分辨率AVHRR Pathfinder卫星海表温度资料,分析了1982-2012年南海及其毗邻海区海表温度（SST）的变化趋势,并给出了近30年该海域SST的气候学特征。结果表明：南海年平均SST随纬度的增加而降低,且越靠近陆地海温梯度越大,等温线呈西南-东北向分布;南海最高、最低SST分别出现在夏季和冬季;夏季中南半岛和海南岛东侧存在相对低温区,应与西南季风和地转偏向力共同作用引起的深层冷水涌升有关;近30年南海及毗邻海区年平均SST增温趋势为0.100℃/10a,20世纪90年代末到21世纪初年平均SST处于高值期,最高值出现在1998年;南海海区四季均存在变暖趋势,冬季增温趋势最大,为0.194℃/10a,夏、春季次之,分别为0.121℃/10a和0.107℃/10a,秋季最小,为0.086℃/10a;近30年台湾海峡和中国大陆东南沿海增温最显著,最大增温值达到0.7℃/10a以上。