Interannual and Interdecadal Variations in Heat Content of the Upper Ocean of the South China Sea

The vertically averaged temperature (TAV) from surface to 100 m depth of the South China Sea for the period 1959-1988 is analyzed. The results indicate that there is a significant long-term variability from interannual to interdecadal scales in the heat content in the upper ocean. The heat content of the upper ocean of the South China Sea increases evidently in the El Nino year. TAV anomaly in the ocean was negative from the end of 1950's to early 1970's, and then changed to positive. The changes of TAV of the ocean are closely related to ENSO events, the Asian winter monsoon and the tropical atmospheric circulation anomalies.

The Relationship between the Interdecadal Variation of Summer Precipitation and Its Interannual Variability over the Middle and Lower Reaches of the Yangtze River Valley

The intensity of summer precipitation interannual variability is strongest over the middle and lower reaches of the Yangtze River Valley(MLYRV). The variability is larger than 1.5 mm d–1 and up to 35%–40% of the climatological mean summer precipitation. The relationship between the interdecadal change in the intensity of summer precipitation and its interannual variability over this area is investigated, by analyzing five gauged and re-constructed precipitation datasets. The relationship is found to be very weak over the MLYRV, with a correlation coefficient of only approximately 0.10. The Pacific Decadal Oscillation influences the western North Pacific subtropical high, which is responsible for the interdecadal change in summer precipitation over the MLYRV. However, the precipitation interannual variability is closely related to the ENSO events in the preceding winter due to its impact on the meridional displacement of the East Asian westerly jet. Different physical mechanisms cause different interdecadal variation in the intensity of summer precipitation and its interannual variability, and thus result in a poor relationship.

Interdecadal Change in the Interannual Variation of the Western Edge of the Western North Pacific Subtropical High During Early Summer and the Influence of Tropical Sea Surface Temperature

This study reveals that the interannual variability of the western edge of the western North Pacific(WNP)subtropical high(WNPSH)in early summer experienced an interdecadal decrease around 1990.Correspondingly,the zonal movement of the WNPSH and the zonal extension of the high-pressure anomaly over the WNP(WNPHA)in abnormal years possess smaller ranges after 1990.The different influences of the tropical SSTAs are important for this interdecadal change,which exhibit slow El Nino decaying pattern before 1990 while rapid transformation from El Nino to La Nina after 1990.The early summer tropical SSTAs and the relevant atmospheric circulation anomalies present obvious interdecadal differences.Before 1990,the warm SSTAs over the northern Indian Ocean and southern South China Sea favor the WNPHA through eastward-propagating Kelvin wave and meridional-vertical circulation,respectively.Meanwhile,the warm SSTA over the tropical central Pacific induces anomalous ascent to its northwest through the Gill response,which could strengthen the anomalous descent over the WNP through meridional-vertical circulation and further favor the eastward extension of the WNPHA to central Pacific.After 1990,the warm SSTAs over the Maritime Continent and northern Indian Ocean cause the WNPHA through meridional-vertical and zonal-vertical circulation,respectively.Overall,the anomalous warm SSTs and ascent and the resultant anomalous descent over the WNP are located more westward and southward after 1990 than before 1990.Consequently,the WNPHA features narrower zonal range and less eastward extension after 1990,corresponding to the interdecadal decease in the interannual variability of the western edge of the WNPSH.On the other hand,the dominant oscillation period of ENSO experienced an interdecadal reduction around 1990,contributing to the change of the El Nino SSTA associated with the anomalous WNPSH from slow decaying type to rapid transformation type.

INTERANNUAL AND INTERDECADAL VARIATIONS OF LARGE-SCALE MOISTURE SINKS OVER GUANGDONG

The interannual and interdecadal variations of moisture sinks over Guangdong are discussed with the NCEP/NCAR reanalysis data and observed precipitation data from 1958 to 2004. The results indicate that climatically, the amount of precipitation is larger than that of evaporation in spring and summer. Precipitation and evaporation almost balance each other in autumn and the amount of evaporation is larger than that of precipitation in winter. The interannual signal dominates the variations of moisture sinks in all seasons in Guangdong with a period of three-year oscillation in autumn and winter. Remarkable interdecadal signal characterized by a period of three-decade oscillation can be identified for winter and spring from seasonally averaged moisture sink data and from annually moisture data, with variance percentage larger than 40%. This result indicates that Guangdong is at a transitional stage from positive anomalies to negative anomalies. The moisture sink anomalies in winter and following spring over Guangdong are usually in-phase. Besides, there exist periodic oscillations with periods of 10 to 15 years in summer and autumn. The positive (negative) anomalies of moisture sinks over Guangdong are due to the intensified (weakened) moisture from the tropical areas being transported to the Southern China, accompanied by an intensified (weakened) moisture convergence.

Diversity on the Interannual Variations of Spring Monthly Precipitation in Southern China and the Associated Tropical Sea Surface Temperature Anomalies

There is a continuous and relatively stable rainy period every spring in southern China(SC).This spring precipitation process is a unique weather and climate phenomenon in East Asia.Previously,the variation characteristics and associated mechanisms of this precipitation process have been mostly discussed from the perspective of seasonal mean.Based on the observed and reanalysis datasets from 1982 to 2021,this study investigates the diversity of the interannual variations of monthly precipitation in spring in SC,and focuses on the potential influence of the tropical sea surface temperature(SST)anomalies.The results show that the interannual variations of monthly precipitation in spring in SC have significant differences,and the correlations between each two months are very weak.All the interannual variations of precipitation in three months are related to a similar western North Pacific anomalous anticyclone(WNPAC),and the southwesterlies at the western flank of WNPAC bring abundant water vapor for the precipitation in SC.However,the WNPAC is influenced by tropical SST anomalies in different regions each month.The interannual variation of precipitation in March in SC is mainly influenced by the signal of El Nino-Southern Oscillation,and the associated SST anomalies in the equatorial central-eastern Pacific regulate the WNPAC through the Pacific-East Asia(PEA)teleconnection.In contrast,the WNPAC associated with the interannual variation of precipitation in April can be affected by the SST anomalies in the northwestern equatorial Pacific through a thermally induced Rossby wave response.The interannual variation of precipitation in May is regulated by the SST anomalies around the western Maritime Continent,which stimulates the development of low-level anomalous anticyclones over the South China Sea and east of the Philippine Sea by driving anomalous meridional vertical circulation.

Interdecadal Variations of the March Atmospheric Heat Source over the Southeast Asian Low-Latitude Highlands

Based on the fifth-generation reanalysis dataset from the European Centre for Medium-Range Weather Forecasts for 1979–2019,we investigated the effects of the circumglobal teleconnection(CGT)on the interdecadal variation of the March atmospheric heat source(AHS)over the Southeast Asian low-latitude highlands(SEALLH).The dominant mode of the March AHS over the SEALLH features a monopole structure with an 8–11-year period.Decadal variations in the AHS make an important contribution to the 11-year low-pass filtered component of the AHS index,whichexplains 54.3%of the total variance.The CGT shows a clear interdecadal variation,which explains 59.3%of the total variance.The March AHS over the SEALLH is significantly related to the CGT on interdecadal timescales.When the CGT is optimally excited by a significant cyclonic vorticity source near northern Africa(i.e.,in its positive phase),the SEALLH is dominated by anomalous southerly winds and ascending motions on the east of the anomalous cyclone.The enhanced advection and upward transfer result in a high-enthalpy air mass that converges into and condenses over the SEALLH,leading to a largerthan-average March AHS over this region.The key physical processes revealed by this diagnostic analysis are supported by numerical experiments.

Interdecadal Change in the Interannual Variability of South China Sea Summer Monsoon Intensity

The interdecadal change in the interannual variability of the South China Sea summer monsoon(SCSSM)intensity and its mechanism are investigated in this study.The interannual variability of the low-level circulation of the SCSSM has experienced a significant interdecadal enhancement around the end of the 1980s,which may be attributed to the interdecadal changes in the evolution of the tropical Indo-Pacific sea surface temperature(SST)anomalies and their impacts on the SCSSM.From 1961 to 1989,the low-level circulation over the South China Sea is primarily affected by the SST anomalies in the tropical Indian Ocean via the mechanism of Kelvin-wave-induced Ekman divergence.While in 1990 to 2020,the impacts of the summer SST anomalies in the Maritime Continent and the equatorial central to eastern Pacific on the SCSSM are enhanced,via anomalous meridional circulation and Mastuno-Gill type Rossby wave atmospheric response,respectively.The above interdecadal changes are closely associated with the interdecadal changes in the evolution of El Niño–Southern Oscillation(ENSO)events.The interdecadal variation of the summer SST anomalies in the developing and decaying phases of ENSO events enhances the influence of the tropical Indo-Pacific SST on the SCSSM,resulting in the interdecadal change in the interannual variability of the SCSSM.

Interannual Variation and Statistical Prediction of Summer Dry and Hot Days in South China from 1970 to 2018

The frequent occurrence of dry and hot(DH)days in South China in summer has a negative impact on social development and human health.This study explored the variation characteristics of DH days and the possible reasons for this knotty problem.The findings revealed a notable increase in the number of DH days across most stations,indicating a significant upward trend.Additionally,DH events were observed to occur frequently.The number of DH days increased during 1970-1990,decreased from 1991 to 1997,and stayed stable after 1997.The key climate factors affecting the interannual variability of the number of DH days were the Indian Ocean Basin warming(IOBW)in spring and the East Asian Summer Monsoon(EASM).Compared with the negative phase of IOBW,in the positive phase of IOBW,500 hPa and 850 hPa geopotential height enhanced,the West Pacific subtropical high strengthened and extended abnormally to the west,more solar radiation reached the surface,surface outgoing longwave radiation increased,and there was an anomalous anticyclone in eastern South China.The atmospheric circulation characteristics of the positive and negative phases of ESAM were opposite to those of IOBW,and the abnormal circulation of the positive(negative)phases of ESAM was unfavorable(favorable)for the increase in the number of DH days.A long-term prediction model for the number of summer DH days was established using multiple linear regression,incorporating the key climate factors.The correlation coefficient between the observed and predicted number of DH days was 0.65,and the root-mean-square error was 2.8.In addition,independent forecasts for 2019 showed a deviation of just 1 day.The results of the independent recovery test confirmed the stability of the model,providing evidence that climatic factors did have an impact on DH days in South China.

Interdecadal change and projection of the relationship between spring Arctic Oscillation and summer precipitation in the Yangtze River valley in CMIP6 models

评估了20个CMIP6模式对春季北极涛动(AO)与长江流域夏季降水(YRP)关系的模拟能力.结果表明, 4个模式(ACCESS-ESM1-5, CMC-CM2-SR5, MRI-ESM2-0, NorESM2-LM))能合理模拟出1990年代后期AO-YRP关系的减弱. 1980-1998年,当春季AO位于正位相时,夏季东亚急流北移,长江流域为异常下沉运动,同时西太平洋副热带高压减弱,减少向长江流域的水汽输送,结果导致降水减少. 1999-2014年,上述大气环流与春季AO的联系不显著,从而减弱AO-YRP的关系.利用这四个模式进一步预估了RCP4.5情景下2015-2100年期间AO-YRP的关系.两者在2015-2040年为显著负相关关系,随后再次减弱.

Influence of Monsoon over the Warm Pool on Interannual Variation on Tropical Cyclone Activity over the Western North Pacific

The relationship between the interannual variation in tropical cyclone （TC） activity over the western North Pacific （WNP） and the thermal state over the warm pool （WP） is examined in this paper. The results show that the subsurface temperature in the WP is well correlated with TC geographical distribution and track type. Their relation is linked by the East Asian monsoon trough. During the warm years, the westward-retreating monsoon trough creates convergence and vorticity fields that are favorable for tropical cyclogenesis in the northwest of the WNP, whereas more TCs concentrating in the southeast result from eastward penetration of the monsoon trough during the cold years. The steering flows at 500 hPa lead to a westward displacement track in the warm years and recurving prevailing track in the cold years. The two types of distinct processes in the monsoon environment triggering tropical cyclogenesis are hypothesized by composites centered for TC genesis location corresponding to two kinds of thermal states of the WP. During the warm years, low-frequency intraseasonal oscillation is active in the west of the WNP such that eastward-propagating westerlies cluster TC genesis in that region. In contrast, during the cold years, the increased cyclogenesis in the southeast of the WNP is mainly associated with tropical depression type disturbances transiting from equatorially trapped mixed Rossby gravity waves. Both of the processes may be fundamental mechanisms for the inherent interannual variation in TC activity over the WNP.

Possible Impacts of the Arctic Oscillation on the Interdecadal Variation of Summer Monsoon Rainfall in East Asia

The influences of the wintertime AO (Arctic Oscillation) on the interdecadal variation of summer monsoon rainfall in East Asia were examined. An interdecadal abrupt change was found by the end of the 1970s in the variation of the AO index and the leading principal component time series of the summer rainfall in East Asia. The rainfall anomaly changed from below normal to above normal in central China, the southern part of northeastern China and the Korean peninsula around 1978. However, the opposite interdecadal variation was found in the rainfall anomaly in North China and South China. The interdecadal variation of summer rainfall is associated with the weakening of the East Asia summer monsoon circulation. It is indicated that the interdecadal variation of the AO exerts an influence on the weakening of the monsoon circulation. The recent trend in the AO toward its high-index polarity during the past two decades plays important roles in the land-sea contrast anomalies and wintertime precipitation anomaly. The mid- and high-latitude regions of the Asian continent are warming, while the low-latitude regions are cooling in winter and spring along with the AO entering its high-index polarity after the late 1970s. In the meantime, the precipitation over the Tibetan Plateau and South China is excessive, implying an increase of soil moisture. The cooling tendency of the land in the southern part of Asia will persist until summer because of the memory of soil moisture. So the warming of the Asian continent is relatively slow in summer. Moreover, the Indian Ocean and Pacific Ocean, which are located southward and eastward of the Asian land, are warming from winter to summer. This suggests that the contrast between the land and sea is decreased in summer. The interdecadal decrease of the land-sea heat contrast finally leads to the weakening of the East Asia summer monsoon circulation.

Interannual and Decadal Variations of Snow Cover overQinghai-Xizang Plateau and Their Relationships to Summer Monsoon Rainfall in China

Interannual and decadal variations of winter snow cover over the Qinghai-Xizang Plateau (QXP) are analyzed by using monthly mean snow depth data set of 60 stations over QXP for the period of 1958 through 1992. It is found that the winter snow cover over QXP bears a pronounced quasi-biennial oscillation, and it underwent an obvious decadal transition from a poor snow cover period to a rich snow cover period in the late 1970’s during the last 40 years. It is shown that the summer rainfall in the eastern China is closely associated with the winter snow cov-er over QXP not only in the interannual variation but also in the decadal variation. A clear relationship ex-ists in the quasi-biennial oscillation between the summer rainfall in the northern part of North China and the southern China and the winter snow cover over QXP. Furthermore, the summer rainfall in the four cli-mate divisions of Qinling-Daba Mountains, the Yangtze-Huaihe River Plain, the upper and lower reaches of the Yangtze River showed a remarkable transition from drought period to rainy period in the end of 1970’s, in good correspondence with the decadal transition of the winter snow cover over QXP. Key words Snow cover over Qinghai-Xizang Plateau - Summer monsoon rainfall in China - Interannual and decadal variations This study was supported by the National Key Programme for Developing Basic Sciences (G 1998040900 Part I).

Large-scale Circulation Anomalies Associated with Interannual Variation in Monthly Rainfall over South China from May to August

Interannual variation in summer rainfall over South China （SC） was investigated on the monthly timescale.It was found that monthly rainfall from May to August exhibits different features of variation,and the amounts are basically independent of each other.There is a significant negative correlation,however,between May and July SC rainfall,which is partially related to the developing phases of ENSO events.It was also found that stronger （weaker） lower-tropospheric winds over SC and the upstream parts are responsible for more （less） SC rainfall in every month from May to August.Despite this monthly consistent enhancement of horizontal winds,the wind anomalies exhibit distinct differences between May-June and July-August,due to the remarkable change in climatological winds between these two periods.More SC rainfall is associated with a lower-tropospheric anticyclonic anomaly over the SCS and the Philippine Sea in May and June,but with a cyclonic anomaly centered over SC in July and August.

A Review of Decadal/Interdecadal Climate Variation Studies in China

Decadal/interdecadal climate variability is an important element in the CLIVAR (Climate Variability and Predictability) and has received much attention in the world. Many studies in relation to interdecadal variation have also been completed by Chinese scientists in recent years. In this paper, an introduction in outline for interdecadal climate variation research in China is presented. The content includes the features of interdecadal climate variability in China, global warming and interdecadal temperature variability, the NAO (the North Atlantic Oscillation)/NPO (the North Pacific Oscillation) and interdecadal climate variation in China, the interdecadal variation of the East Asian monsoon, the interdecadal mode of SSTA (Sea Surface Temperature Anomaly) in the North Pacific and its climate impact, and abrupt change feature of the climate.

Decadal/Interdecadal Variations of the Ocean Temperature and its Impacts on Climate

Decadal/interdecadal climate variability is an important research focus of the CLIVAR Program and has been paid more attention. Over recent years, a lot of studies in relation to interdecadal climate variations have been also completed by Chinese scientists. This paper presents an overview of some advances in the study of decadal/interdecadal variations of the ocean temperature and its climate impacts, which includes interdccadal climate variability in China, the interdecadal modes of sea surface temperature （SST） anomalies in the North Pacific, and in particular, the impacts of interdecadal SST variations on the Asian monsoon rainfall. As summarized in this paper, some results have been achieved by using climate diagnostic studies of historical climatic datasets. Two fundamental interdecadal SST variability modes （7- 10-years mode and 25 35-years mode） have been identified over the North Pacific associated with different anomalous patterns of atmospheric circulation. The southern Indian Ocean dipole （SIOD） shows a major feature of interdecadal variation, with a positive （negative） phase favoring a weakened （enhanced） Asian summer monsoon in the following summer. It is also found that the China monsoon rainfall exhibits interdecadal variations with more wet （dry） monsoon years in the Yangtze River （South China and North China） before 1976, but vice versa after 1976. The weakened relationship between the Indian summer rainfall and ENSO is a feature of interdecadal variations, suggesting an important role of the interdecadal variation of the SIOD in the climate over the south Asia and southeast Asia. In addition, evidence indicates that the climate shift in the 1960s may be related to the anomalies of the North Atlantic Oscillation （NAO） and North Pacific Oscillation （NPO）. Overall, the present research has improved our understanding of the decadal/interdecadal variations of SST and their impacts on the Asian monsoon rainfall. However, the research also highlights a number of problems for future research, in particular the mechanisms responsible for the monsoon long4erm predictability, which is a great challenge in climate research.

The Interannual Variation in Monthly Temperature over Northeast China during Summer

The interannual variations of summer surface air temperature over Northeast China （NEC） were investigated through a month-to-month analysis from May to August. The results suggested that the warmer temperature over NEC is related to a local positive 500-hPa geopotential height anomaly for all four months. However, the teleconnection patterns of atmospheric circulation anomalies associated with the monthly surface air temperature over NEC behave as a distinguished subseasonal variation, although the local positive height anomaly is common from month to month. In May and June, the teleconnection pattern is characterized by a wave train in the upper and middle troposphere from the Indian Peninsula to NEC. This wave train is stronger in June than in May, possibly due to the positive feedback between the wave train and the South Asian rainfall anomaly in June, when the South Asian summer monsoon has been established. In July and August, however, the teleconnection pattern associated with the NEC temperature anomalies is characterized by an East Asia/Pacific （EAP） or Pacific/Japan （PJ） pattern, with the existence of precipitation anomalies over the Philippine Sea and the South China Sea. This pattern is much clearer in July corresponding to the stronger convection over the Philippine Sea compared to that in August.

Analysis of interdecadal variation of tropical Pacific thermocline based on assimilated data

The interdecadal variation of Pacific thermocline represented by depth anomalies of 25σθ isopycnal surface calculated from SODA data set is analyzed. The climatological depth of 25σθ isopycnal surface is quite close to the depth of 20 ℃ isotherm in the tropical Pacific. The EOF1 mode of the 25σθ isopycnal surface accounts for 26. 4% of the total variance and its associated pattern is of east-west direction. The centers of positive and negative extremes are located near 10oS over the southern Pacific and the correlation coefficient with zero-lag between the corresponding EOF1 time coefficient and PDO index is -0.67. This shows that there is very close relation between the southern tropical Pacific and PDO. The wavelet analysis of detrended EOF1 time coefficient reveals that there are two dominant time scales of about 3～7 and 30 a respectively. An apparent abruptness of mean value occurred in the late 1970s. EOF2 mode accounts for 12.4% of the total variance and its pattern is an ENSO-related one. The correlation coefficient between the EOF2 time coefficient and NINO3 index is -0.68. The wavelet analysis of EOF2 time coefficient reveals that there are two leading time scales of about 2～7 and 10～15 a respectively. On an interdecadal scale, the zonal change is consistent along the equator and is seesaw along 10oS; there is consistent polarity in the tropics along 165oE, but reverse polarity between around equator and other tropical region along 120oW. In all the four profiles mentioned above, the regime shift occurred in the late 1970s. The evolving characteristics of anomalies can be explained mostly by the anomalies of ocean currents during a complete cycle on an interdecadal scale.

Prediction of the Asian-Australian Monsoon Interannual Variations with the Grid-Point Atmospheric Model of IAP LASG(GAMIL)

Seasonal prediction of Asian-Australian monsoon （A-AM） precipitation is one of the most important and challenging tasks in climate prediction. In this paper, we evaluate the performance of Grid Atmospheric Model of IAP LASG （GAMIL） on retrospective prediction of the A-AM interannual variation （IAV）, and determine to what extent GAMIL can capture the two major observed modes of A-AM rainfall IAV for the period 1979-2003. The first mode is associated with the turnabout of warming （cooling） in the Nifio 3.4 region, whereas the second mode leads the warming/cooling by about one year, signaling precursory conditions for ENSO. We show that the GAMIL one-month lead prediction of the seasonal precipitation anomalies is primarily able to capture major features of the two observed leading modes of the IAV, with the first mode better predicted than the second. It also depicts the relationship between the first mode and ENSO rather well. On the other hand, the GAMIL has deficiencies in capturing the relationship between the second mode and ENSO. We conclude： （1） successful reproduction of the E1 Nifio-excited monsoon-ocean interaction and E1 Nifio forcing may be critical for the seasonal prediction of the A-AM rainfall IAV with the GAMIL; （2） more efforts are needed to improve the simulation not only in the Nifio 3.4 region but also in the joining area of Asia and the Indian-Pacific Ocean; （3） the selection of a one-tier system may improve the ultimate prediction of the A-AM rainfall IAV. These results offer some references for improvement of the GAMIL and associated seasonal prediction skill.

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. Key words North Atlantic Oscillation (NAO) - North Pacific Oscillation (NPO) - Climate Jump - Interdecadal climate variation This work was supported by National Key Basic Science Program in China (G1998040903), Chinese Academy of Science and the National Natural Science Fundation of China (Grant No.49823002).The authors are also grateful to Ms. Wang Xuan for typing the manuscript.

Numerical Simulation of the Impact of Vegetation Index on the Interannual Variation of Summer Precipitation in the Yellow River Basin

Two sets of numerical experiments using the coupled National Center for Environmental Prediction General Circulation Model （NCEP/GCM T42L18） and the Simplified Simple Biosphere land surface scheme （SSiB） were carried out to investigate the climate impacts of fractional vegetation cover （FVC） and leaf area index （LAI） on East Asia summer precipitation, especially in the Yellow River Basin （YRB）. One set employed prescribed FVC and LAI which have no interannual variations based on the climatology of vegetation distribution; the other with FVC and LAI derived from satellite observations of the International Satellite Land Surface Climate Project （ISLSCP） for 1987 and 1988. The simulations of the two experiments were compared to study the influence of FVC, LAI on summer precipitation interannual variation in the YRB. Compared with observations and the NCEP reanalysis data, the experiment that included both the effects of satellite-derived vegetation indexes and sea surface temperature （SST） produced better seasonal and interannual precipitation variations than the experiment with SST but no interannual variations in FVC and LAI, indicating that better representations of the vegetation index and its interannual variation may be important for climate prediction. The difference between 1987 and 1988 indicated that with the increase of FVC and LAI, especially around the YRB, surface albedo decreased, net surface radiation increased, and consequently local evaporation and precipitation intensified. Further more, surface sensible heat flux, surface temperature and its diurnal variation decreased around the YRB in response to more vegetation. The decrease of surface-emitting longwave radiation due to the cooler surface outweighed the decrease of surface solar radiation income with more cloud coverage, thus maintaining the positive anomaly of net surface radiation. Further study indicated that moisture flux variations associated with changes in the general circulation also contributed to the precipitation interannual variation.