Regional-scale Surface Air Temperature and East Asian Summer Monsoon Changes during the Last Millennium Simulated by the FGOALS-gl Climate System Model

The spatial patterns and regional-scale surface air temperature （SAT） changes during the last millennium,as well as the variability of the East Asian summer monsoon （EASM） were simulated with a low-resolution version of Flexible Global Ocean-Atmosphere-Land-Sea-ice （FGOALS-gl） model.The model was driven by both natural and anthropogenic forcing agents.Major features of the simulated past millennial Northern Hemisphere （NH） mean SAT variations,including the Medieval Climate Anomaly （MCA）,the Little Ice Age （LIA） and the 20th Century Warming （20CW）,were generally consistent with the reconstructions.The simulated MCA showed a global cooling pattern with reference to the 1961-90 mean conditions,indicating the 20CW to be unprecedented over the last millennium in the simulation.The LIA was characterized by pronounced coldness over the continental extratropical NH in both the reconstruction and the simulation.The simulated global mean SAT difference between the MCA and LIA was 0.14°C,with enhanced warming over high-latitude NH continental regions.Consistencies between the simulation and the reconstruction on regional scales were lower than those on hemispheric scales.The major features agreed well between the simulated and reconstructed SAT variations over the Chinese domain,despite some inconsistency in details among different reconstructions.The EASM circulation during the MCA was stronger than that during the LIA The corresponding rainfall anomalies exhibited excessive rainfall in the north but deficient rainfall in the south.Both the zonal and meridional thermal contrast were enhanced during the MCA.This temperature anomaly pattern favored a stronger monsoon circulation.

Global Annual Mean Surface Air Temperature Anomalies and Their Link with Indian Summer Monsoon Failures

Analysis of the global mean annual temperature anomalies based on land and marine data for the last 88 years (1901-1988) of this century has been carried out with a view to find any relationship with failures in Indian summer monsoon rainfall. On the climatological scale (i.e. 30 years) it has been noticed that there is an abnormal increase in the frequency of drought years during epochs of global warming and cooling, while it is considerably less when global temperatures are near normal. Results are unchanged even when the data are filtered out for ENSO (El-Nino Southern Oscillation) effect.It has also been noticed that during warm and cold epochs in global temperatures the amount of summer monsoon rainfall decreases as compared to the rainfall during a normal temperature epoch.

Enhancement of the Summer North Atlantic Oscillation Influence on Northern Hemisphere Air Temperature

This study investigates the relationship between the summer North Atlantic Oscillation （SNAO） and the simultaneous Northern Hemisphere （NH） land surface air temperature （SAT） by using the Climate Research Unit （CRU） data. The results show that the SNAO is related to NH land SAT, but this linkage has varied on decadal timescales over the last 52 years, with a strong connection appearing after the late 1970s, but a weak connection before. The mechanism governing the relationship between the SNAO and NH land SAT is discussed based on the NCEP/NCAR reanalysis data. The results indicate that such a variable relationship may result from changes of the SNAO mode around the late 1970s. The SNAO pattern was centered mainly over the North Atlantic before the late 1970s, and thus had a weak influence on the NH land SAT. But after the late 1970s, the SNAO pattern shifted eastward and its southern center was enhanced in magnitude and extent, which transported the SNAO signal to the North Atlantic surrounding continents and even to central East Asia via an upper level wave train along the Asian jet.

Impact of Spatial Inhomogeneity in Atmospheric CO_(2) Concentration on Surface Air Temperature Variations

Atmospheric CO_(2) concentration is characterized by spatial inhomogeneity and seasonal variability.The response of surface air temperature(SAT)to the inhomogeneity in CO_(2) concentration globally and regionally remains elusive.In this study,the BCC-CSM2-MR climate model was used to investigate the differences in global SAT in response to the spatially inhomogeneous distribution of atmospheric CO_(2) concentration.The analysis was based on three historical experiments(Hist_1dCO_(2),Hist_2dCO_(2),and Hist_3dCO_(2))conducted separately under the forcing of globally homogeneous,zonally homogeneous,and wholly spatially inhomogeneous CO_(2) concentrations from 1850 to 2014,derived from 12 Earth System Models of the Coupled Model Intercomparison Project Phase 6.The simulation results revealed similar trends of evolution in the global mean SATs in the 20th century under the three CO_(2) concentration distributions,and showed that the simulated historical SATs considering the meridional inhomogeneity of CO_(2) concentration in Hist_2dCO_(2) and the wholly spatial inhomogeneity in Hist_3dCO_(2) were more consistent with the observations.Compared with the results of Hist_1dCO_(2),the SATs in Hist_2dCO_(2) were warmer over land in the mid–high latitudes of the Northern Hemisphere(NH)than over other land areas.Further consideration of the zonally inhomogeneous CO_(2) concentration in Hist_3dCO_(2) revealed generally colder SATs over the NH mid–high-latitude ocean than over land at the same latitudes,and even the zonal mean SATs in the NH were slightly colder than those in Hist_2dCO_(2).These differences are ascribed to the uneven distribution of CO_(2) concentration along the same latitude in the NH in Hist_3dCO_(2),which leads to strong large-scale fluctuations in the atmospheric circulation.Eurasia is the region with the highest concentration of atmospheric CO_(2),which leads to remarkable regional SAT warming owing to enhanced downward longwave radiation.Warmer SATs in Eurasia in winter will further strengthen the northwesterly winds over eastern Asia,resulting in an increase in sea ice and strengthened cold SAT anomalies over the northern North Pacific.The simulated varied responses of the atmospheric circulation and SAT to inhomogeneous CO_(2) forcing highlight the imperative need for refined representation of the inhomogeneity of the atmospheric CO_(2) distribution in climate models for more accurate assessment of climate change.

Satellite-observed trends in the Arctic sea ice concentration for the period 1979–2016

Arctic sea ice cover has decreased dramatically over the last three decades. This study quanti?es the sea ice concentration(SIC) trends in the Arctic Ocean over the period of 1979–2016 and analyzes their spatial and temporal variations. During each month the SIC trends are negative over the Arctic Ocean, wherein the largest(smallest) rate of decline found in September(March) is-0.48%/a(-0.10%/a).The summer(-0.42%/a) and autumn(-0.31%/a) seasons show faster decrease rates than those of winter(-0.12%/a) and spring(-0.20%/a) seasons. Regional variability is large in the annual SIC trend. The largest SIC trends are observed for the Kara(-0.60%/a) and Barents Seas(-0.54%/a), followed by the Chukchi Sea(-0.48%/a), East Siberian Sea(-0.43%/a), Laptev Sea(-0.38%/a), and Beaufort Sea(-0.36%/a). The annual SIC trend for the whole Arctic Ocean is-0.26%/a over the same period. Furthermore, the in?uences and feedbacks between the SIC and three climate indexes and three climatic parameters, including the Arctic Oscillation(AO), North Atlantic Oscillation(NAO), Dipole anomaly(DA), sea surface temperature(SST), surface air temperature(SAT), and surface wind(SW), are investigated. Statistically, sea ice provides memory for the Arctic climate system so that changes in SIC driven by the climate indices(AO, NAO and DA) can be felt during the ensuing seasons. Positive SST trends can cause greater SIC reductions, which is observed in the Greenland and Barents Seas during the autumn and winter. In contrast, the removal of sea ice(i.e., loss of the insulating layer) likely contributes to a colder sea surface(i.e., decreased SST), as is observed in northern Barents Sea. Decreasing SIC trends can lead to an in-phase enhancement of SAT, while SAT variations seem to have a lagged in?uence on SIC trends. SW plays an important role in the modulating SIC trends in two ways: by transporting moist and warm air that melts sea ice in peripheral seas(typically evident inthe Barents Sea) and by exporting sea ice out of the Arctic Ocean via passages into the Greenland and Barents Seas, including the Fram Strait, the passage between Svalbard and Franz Josef Land(S-FJL),and the passage between Franz Josef Land and Severnaya Zemlya(FJL-SZ).

INFLUENCE OF THE SURFACE AIR TEMPERATURE OVER ASIAN-PACIFIC REGION ON THE SUMMERTIME NORTHEASTERN ASIAN BLOCKING HIGH

Synthesis analysis and singular value decomposition (SVD) methods were used to study the impact of surface air temperature (SAT) over Asian-Pacific region on the summertime northeastern Asian blocking high (NABH) with NCEP/NCAR Reanalysis Data.The results showed that 500 hPa geopotential height and SAT fields over Asian-Pacific region shared the similar pattern of East Asian Pacific (EAP) wave train;there was steady remote response relationship between the EAP wave train in summer and the '+-+' pattern of tropical SAT in zonal direction from former winter to summer;there were two relative negative(positive) Walker circulations over the tropical Indian Ocean and Pacific when being more(less) summertime NABH. The influence of sea surface temperature anomaly (SSTA) on the summertime NABH was possibly as follows.The special distribution of SSTA in tropical zonal direction continuously forced the tropical convection and zonal circulation from former winter to summer,and led them to act anomaly.Finally the abnormal conditions were transported to middle-high latitudes through EAP wave train and yielded the advantageous or disadvantageous atmospheric circulation background for the summertime NABH.

Intraseasonal Variability of Summertime Surface Air Temperature over Mid-High-Latitude Eurasia and Its Prediction Skill in S2S Models

Features of the dominant modes of surface air temperature(SAT)on the intraseasonal timescale over the mid-highlatitude Eurasia(MHE)during boreal summer(June-September)are investigated based on the ERA5 reanalysis data from 1979 to 2016.The intraseasonal variability(ISV)of SAT over MHE is primarily characterized by an eastward propagation along 60°N,which is found to impact the regional weather in China,including summertime extreme hot and cool events.The forecast skill and potential predictability of the ISV of SAT over MHE are assessed for 5 dynamical models that have participated in the subseasonal-to-seasonal(S2 S)prediction project,by analyzing12 years’(1999-2010)model reforecast/hindcast data.By using the principal component(PC)index of the leading intraseasonal SAT modes as a predictand,we found that the forecast skill for ISV of SAT can reach out to 11-17 days,and the ECMWF model exhibits the best score.All the S2 S models tend to show 1)a relatively higher skill for strong intraseasonal oscillation(ISO)cases,2)a systematic underestimate of the amplitude of the SAT ISV signal,and 3)different skills during different phases of ISO cases.Analysis of potential predictability based on the perfectmodel assumption reveals a 4-6-day skill gap for most models,and the skill gap also varies among different phases of ISO events.The results imply the need for continued development of operational forecasting systems to improve the actual prediction skills for the ISV of SAT over MHE.

Impacts of the stratospheric quasi-biennial oscillation on the tropospheric circulation and climate in the Northeast Asia-North Pacific region in early summer

本文研究了平流层准两年振荡(QBO)对东北亚-北太平洋地区初夏对流层环流和地表气温的影响.在QBO西风位相年,东北亚至北太平洋地区存在一支由QBO引发的平均经向环流异常,该经向环流异常可在东北亚至北太平洋地区激发正涡度,并形成异常气旋式环流.气旋左侧出现的异常偏北风导致6月东北亚地表气温下降.QBO东风位相年的结果与西风位相年大致相反.这些结果为QBO对热带外地区天气,气候的影响提供了新的证据,并为东北亚初夏地表气温的预测提供了新的线索。

Interdecadal variations of the East Asian winter surface air temperature and possible causes

Using the NCEP/NCAR and JRA-25 monthly analysis data from 1979 to 2011,this paper analyzes the interdecadal variations of winter(Dec.–Feb.)mean surface air temperature(SAT)over East Asia by means of the empirical orthogonal function(EOF)analysis method.Two dominant modes were extracted,with the leading mode basically depicting a sign consistent SAT variation and the second mode describing a meridional dipole structure between the northern and southern parts of East Asia.These two modes can explain more than 60%of the variance.The leading mode is closely related to the intensity of Siberian high and the East Asian winter monsoon.The second mode exhibits a notable interdecadal shift in the late 1990s,with a turning point around1996/1997.Winter SAT in the northern(southern)part of East Asia tends to be cooler(warmer)since the late 1990.Winter sea level pressure(SLP)differences between 1997–2011 and 1979–1996 show negative(positive)anomalies over southern(northern)Eurasia.At 500-hPa,an anomalous blocking high occurs over northern Eurasia,while a cyclone anomaly appears over northern East Asia.In addition,the upper-level East Asian jet stream tends to shift northward and become stronger after the late 1990.Indeed,the interdecadal shift of winter SAT over East Asia is dynamical consistent with changes of the large-scale atmospheric circulation in the late 1990s.The result indicates that previous autumn sea surface temperature(SST)in the North Atlantic Ocean,the Northern Indian Ocean and the western North Pacific Ocean,as well as sea ice concentration(SIC)in the northern Eurasia marginal seas and the Beaufort Sea also experienced obvious changes in the late 1990s.In particular,the interdecadal shifts of both SST in the North Atlantic Ocean and SIC in the Arctic Ocean and its marginal seas are well coherent with that of the winter SAT over East Asia.The results indicate that the interdecadal shift of East Asian winter SAT may be related to changes in the North Atlantic SST and the Arctic SIC in the late 1990s.

基于空间化技术对中国近50年平均气温时空演变特征的研究

结合GIS空间化技术,对中国近50年平均气温数据进行定量化的分析,并分析其时空演变规律。采用空间化气候值+年际距平空间插值法生成中国1951—2001年分辨率为10 km×10 km的年、季平均气温空间化数据,通过对近50年空间化数据的分析,认为近50年中,年、季的全国平均气温都表现出显著增温趋势,冬季增幅最大,为0.313℃/10a,夏季增幅最小,为0.152℃/10a,年平均气温增幅为0.208℃/10a。1980年代中期以后增温趋势更加明显。从空间分布看,我国西南地区及西藏东南部和新疆西天山中段在不同季节都是主要的降温区域,而北方大部和西藏中西部地区在不同季节都表现为较强的增温趋势,我国东南地区在不同季节温度变化并不稳定,增温或降温的幅度都很小。暖冬事件在北方发生比较频繁,四川及云南部分地区较少,全国发生面积呈逐渐增大的趋势,增幅为国土面积的8.6%/10a。冷夏在新疆南部、西藏西北部和东南部以及江淮一带发生次数较多,辽宁南部、新疆沙漠地区、西藏中部、青海东部、四川大部分地区以及长江以南广大地区最少。全国发生冷夏的面积不断减小,50年平均减幅约为国土面积的5.8%/10a。

冬季亚洲大陆的热力差异对亚洲季风活动的影响

亚洲冬季地面的热力状况与冬季风活动有关,对后期的天气气候变化也有重要的作用。作者用EOF方法分析了亚洲冬季地面气温的时空特征,发现第二模态表明东北亚和南亚地区的地面气温有反相变化的特征并具有明显的年代际变化。进一步研究发现,这种南亚东北亚的热力差特征与亚洲夏季风强弱有非常好的对应关系,籍此定义了一个大陆冬季南亚—东北亚热力差指数。分析表明热力差指数有非常明显的年代际变化,根据这一特征,进一步研究了夏季北半球大尺度环流和中国气候的年代际变化,发现其年代际变化对前冬亚洲大陆热力差指数的年代际特征敏感,相应大陆正、负热力差指数年代,东亚季风的变化特征几乎完全相反:南亚东北亚热力差正(负)指数年代,东亚夏季风较强(弱)。热力差指数对中国夏季降水的年代际变化也有重要影响,正(负)指数年代,中国夏季降水主要以第1(2)类雨型为主。同时,作者还分析了低纬度热带地区海温和对流活动对大陆冬季南亚东北亚热力差异响应的滞后性特征。

春季格陵兰海冰与夏季中国气温和降水的关系

采用英国 Hadley中心的 GISST海冰面积资料、NCEP/NCAR再分析资料以及中国 1 60站气温和降水资料 ,分析了春季格陵兰海冰面积与夏季中国区域气温和降水的关系。初步研究表明 ,春季格陵兰海冰面积变化和随后夏季我国黄河长江中下游之间地区气温以及 8月份华北和西南地区降水呈明显正相关 ,而和 6月黄河中上游地区降水则具有明显的负相关。同时 ,春季格陵兰海冰异常时期对应着北半球大气环流的明显变化 。

基于递归小波神经网络的江苏城镇夏季最高气温预报预警技术

针对目前数值天气预报产品释用方法上所存在的释用因子固化,无法应对特殊转折性天气的问题,应用一种基于动态因子检验的递归小波神经网络(Recurrent Wavelet Neural Network,RWNN)对江苏城镇夏季最高气温进行释用。该方法可以自动选取气象要素且无需建立回归方程,具有泛用性好、灵活性高的特点。使用该方法基于T639的2017-2018年6-8月资料建立了江苏省南京、徐州、射阳、常州、苏州5地的最高气温预报预警模型。实验结果表明:南京、徐州、射阳3地模型的TT2和HSS35评分较反向传播神经网络方法分别平均提高了9个百分点和0.15,同时较卡尔曼滤波方法分别平均提高了17个百分点和0.2。

华南及邻近海域春季海陆温差减弱与东亚夏季风强度关系的分析和模拟

利用NCEP/NCAR再分析资料,计算了1948—2006年春季平均地面气温的线性变率,表明其在华南地区为负变率,而在南部海洋则为正变率,即华南及邻近海域的春季海陆温差具有明显的减弱趋势。合成分析表明,其与夏季东亚区域南风的减弱趋势存在一定的联系。采用第三代区域气候模式(ICTP RegCM3)进行了在春季增高华南陆地表面气温和降低南部海洋表面气温的理想状况数值模拟试验,进一步分析华南及其邻近海域春季海陆温差减弱趋势对东亚夏季风强度的影响。模拟结果表明,与控制试验相比,敏感试验模拟的夏季850 hPa风场在中国东部地区表现出南风减弱的特征(差值风场为北风),同时还可发现夏季中国东部及其以东洋面存在一个气旋性差值环流。因此,华南及其邻近海域春季海陆温差的减弱趋势对东亚夏季风强度可能具有一定的影响。

重庆地区极端高温事件的模拟研究

该文使用了中国科学院大气物理研究所大气环流模式IAP AGCM4.1和中尺度数值模式WRF3.2建立的耦合模式(IWRF),利用该耦合模式对1982—2014年重庆夏季气候进行了试验,将模拟结果与NCEP/DOE再分析资料驱动WRF3.2(NWRF)的模拟结果进行了比较,并利用观测资料评估了这2个试验对于重庆极端高温事件的模拟能力。结果表明:(1)2个试验均能较为合理地再现重庆夏季地表气温的气候态特征,IWRF的模拟偏差较大,尤其对于高海拔地区。它们对极端高温事件的模拟存在较大偏差,对日最高气温最大值(TXx),两者的距平分布相似,对暖昼指数(TX90p)和热浪持续指数(HWDI),IWRF的表现好于NWRF。在西部和东南部地区,2个试验对暖昼指数都具有一定的模拟能力;(2)NWRF能够模拟出极端高温指数的年际变化特征,而IWRF表现欠佳;(3)它们都不能模拟出TXx的变化趋势,但是,NWRF能够模拟出HWDI和TX90p的增加趋势。该文的结论可为重庆短期气候预测系统用于极端高温的预测提供一定参考。

1980~2019年中亚夏季地表气温的异常增暖

本文利用1980~2019年NCEP/NCAR全球再分析资料、CRU地表气温资料、积雪覆盖率资料和全球海温资料,分析了中亚夏季地表气温的气候突变及其和北大西洋海温、青藏高原积雪之间的关系。结果表明:中亚夏季地表气温在2005年发生明显的气候突变。标准化的中亚区域平均的气温指数从之前的负位相为主变为之后的正位相为主,表示中亚地区夏季地表气温显著增温。和中亚夏季地表气温异常增温相联系的大气环流场的分析表明,2005年之后,中亚地区西侧的反气旋性环流系统异常增强,该反气旋异常对应的大气下沉增暖以及反气旋异常增强引起的云量减少进而导致向下的短波辐射增加均有利于中亚夏季气温异常升高。进一步的合成分析表明,中亚夏季地表气温在2005年的气候突变和北大西洋中高纬度地区的海表温度的增暖和青藏高原西部积雪的减少有着密切关系。北大西洋中高纬度海表温度增温能激发一个向下游传播的罗斯贝波,青藏高原西部积雪减少能够通过积雪的反照率效应对上空的大气有增温作用,两者均能增强中亚地区上空的反气旋系统,从而有利于中亚夏季地表气温异常偏高。

RegCM3 CORDEX东亚试验模拟和预估的中国夏季温度变化

按照CORDEX(COordinated Regional Downscaling Experiment)计划试验设计要求,利用中国科学院大气物理研究所全球模式FGOALS-g2的数据驱动区域气候模式RegCM3,针对1986~2005年历史气候和2010~2065年RCP8.5排放情景下气候预估,对东亚地区进行了50 km动力降尺度模拟。首先评估了RegCM3模式及驱动模式FGOALS-g2对1986~2005年夏季中国地表气温和极端高温事件的模拟能力,然后比较了两个模式在RCP8.5排放情景下对中国夏季地表气温和极端高温事件预估的变化,重点分析了动力降尺度结果的优势。结果表明,两个模式均能合理再现夏季中国地表气温和极端高温事件的大尺度气候态特征。相对于全球模式,区域模式由于水平分辨率较高,能在刻画地表气温分布的细节上体现出优势。在RCP8.5排放情景下,两个模式预估的三个地表气温指标均显著升高,到21世纪中期(2046~2065年),两个模式预估的全国平均地表气温增幅相当,气温日较差变化均较小。在FGOALS-g2模式预估中,到21世纪中期,三个地表气温指标的增幅相当,气温日较差没有明显变化,东北和青藏高原的地表气温增幅最大。在RegCM3模式预估中,到21世纪中期,中国大部分地区日最高气温(Tmax)增幅大于日最低气温(Tmin)增幅,气温日较差增加;而在青藏高原西部,Tmax的增幅较Tmin偏低,气温日较差减小。在RCP8.5排放情景下,两个模式预估的极端高温事件到21世纪中期也显著增加,RegCM3模式预估的极端高温事件全国平均增幅略高于FGOALS-g2模式的预估。在两个模式的预估中,日最高气温最大值(TXx)、暖昼指数(TX90p)和持续暖期指数(WSDI)变化的空间分布特征与Tmax相似;和当代相比TX90p增加了60%以上,而WSDI增加了一倍以上。

印度洋海温与长江上游夏季风关系的初步分析

对印度洋海温分布的基本特征和长江上游夏季风活动的基本规律进行分析，并作了相关场研究．结果表明，印度洋海温距平与长江上游夏季风综合指数之间反相关密切，索马里海流区、莫桑比克海流区、南印度洋中部海区及菲律宾以东洋面为显著相关区，尤其是索马里海流区和莫桑比克海流区先年秋季的海温距平对长江上游夏季风的活动具有预报意义．这些结果对探讨长江上游夏季风、印度洋海温和长江上游旱涝三者的关系，对三峡水库水文特征的研究具有重要意义．

NORTHERN HEMISPHERIC SUMMER CLIMATIC JUMP IN THE 1960s (Ⅰ)——RAINFALL AND TEMPERATURE

With the conception of the climatic jump, the authors revealed the large-scale characteristics of the abrupt summer climatic change in the Northern Hemisphere in the 1960s. This paper concerns the change of the summer rainfall, air temperature and sea surface temperature in 1951—1980. There was a wide zone including North Africa, northwest India, central China and Japan where the rainfall decreased abruptly in the 1960s while two zones, respectively south and north of the drying zone, experienced increasing rainfall. The temperature decreased abruptly in most of the northern mid-high latitudinal regions and increased significantly in some of the lower-latitudinal regions, leading to a sudden enlarging of the equator-polar thermal difference. It was noted that the climatic jump seemed to occur asynchronously from one region to another.

清江流域水热关系与东亚夏季风的联系

降水(P)与气温(T)之间的关系,即水热关系(PTR),在夏季一定程度上可反映干旱—高温热浪(或洪涝多雨—凉夏)极端气候灾害事件的发生情况。三峡库区内的清江流域,存在发育良好的洞穴,其沉积物中碳氧同位素序列长,可一定程度代表降水或气温信息,存在构造长序列PTR指标的可能性。从现代器测与再分析记录出发,研究清江流域PTR的演变特征和成因,可为利用石笋碳氧同位素构造PTR代用指标提供一些物理基础和启发。本文利用清江流域6个站(巴东、建始、利川、恩施、五峰、宜昌)1960~2016年逐日气温与降水观测资料及NCEP耦合预报模式再分析(CFSR)、日本气象厅55年再分析(JRA55)和欧洲中期天气预报中心再分析(ERA-interim)等3套资料,分析了清江流域PTR季节性差异、年际与年代际变化及其与东亚夏季风的联系。结果表明:1)PTR有明显季节性差异,夏季为显著负相关,其他季节不明显;2)夏季PTR存在明显年代际变化,表现出20~25年准周期振荡特征。在过去的几十年间,1965~1976年和1993~2011年期间水热相关不显著,而1977~1992年为显著负相关,即分别在1974年、1986年、1992年发生了年代际转折;3)夏季PTR年代际变化和东亚夏季风强度有一定的联系。在水热显著负相关时段(1977~1992年),夏季风偏弱;PTR不显著时段(1965~1976年和1993~2011年),夏季风偏强;4)机制上,夏季风减弱,南北方气流交汇位置靠南,清江流域水汽增加,上升运动增强,云量与降水增加,导致地表热通量减少,地面气温下降,PTR为显著负相关。夏季风增强时,南北气流交汇区北移,清江流域水汽减少,下沉运动增强,导致云量减少而地表热通量增加,使得气温上升,进一步使气温垂直递减率增加,降水效率对降水贡献为正,表明气温上升利于降水增加,同时云量/降水对气温的影响减弱,但并未消失,使得PTR不显著。5)太平洋年代际振荡(IPO/PDO)对清江流域夏季PTR起着一定的调制作用。