Evaluating the Brewer–Dobson circulation and its responses to ENSO,QBO,and the solar cycle in different reanalyses

This study compares the climatology and long-term trend of northern winter stratospheric residual mean meridional circulation(RMMC), as well as its responses to El Ni?o-Southern Oscillation(ENSO), stratospheric Quasi Biennial Oscillation(QBO), and solar cycle in ten reanalyses and a stratosphere-resolving model, CESM1-WACCM. The RMMC is a large-scale meridional circulation cell in the stratosphere, usually referred to as the estimate of the Brewer Dobson circulation(BDC). The distribution of the BDC is generally consistent among multiple reanalyses except that the NOAA twentieth century reanalysis(20RC) largely underestimates it. Most reanalyses(except ERA40 and ERA-Interim) show a strengthening trend for the BDC during 1979–2010. All reanalyses and CESM1-WACCM consistently reveal that the deep branch of the BDC is significantly enhanced in El Ni?o winters as more waves from the troposphere dissipate in the stratospheric polar vortex region. A secondary circulation cell is coupled to the temperature anomalies below the QBO easterly center at 50 hPa with tropical upwelling/cooling and midlatitude downwelling/warming, and similar secondary circulation cells also appear between 50–10 hPa and above 10 hPa to balance the temperature anomalies. The direct BDC response to QBO in the upper stratosphere creates a barrier near 30°N to prevent waves from propagating to midlatitudes, contributing to the weakening of the polar vortex. The shallow branch of the BDC in the lower stratosphere is intensified during solar minima, and the downwelling warms the Arctic lower stratosphere. The stratospheric responses to QBO and solar cycle in most reanalyses are generally consistent except in the two 20 CRs.

The IOD-ENSO precursory teleconnection over the tropical Indo-Pacific Ocean:dynamics and long-term trends under global warming

The dynamics of the teleconnection between the Indian Ocean Dipole(IOD) in the tropical Indian Ocean and El Ni?o-Southern Oscillation(ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.The dynamics of the teleconnection between the Indian Ocean Dipole(IOD)in the tropical Indian Ocean and El Ni?o-Southern Oscillation(ENSO)in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations.The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean,which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO.In comparison,lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant,suggesting the short memory of the atmospheric bridge.A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans.The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15%depending on the baroclinic modes.The IOD-ENSO teleconnection is found to get stronger in the past century or so.Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century,which is found sensitive to the global warming forcing.

Interannual wave climate variability in the Taiwan Strait and its relationship to ENSO events

This study investigated the interannual wave climate variability in the Taiwan Strait(TS) and its relationship to the El Ni?o-Southern Oscillation(ENSO) phenomenon using a high-resolution numerical wave model. The results showed the interannual variability of significant wave height(SWH) in the TS, which exhibits significant spatial and seasonal variations, is typically weaker than the seasonal variability. The standard deviation of the interannual SWH anomaly(SWHA) showed similar spatial variations in the TS throughout the year, being largest in the middle of the strait and decreasing shoreward, except in summer, when there was no local maximum in the middle of the TS. Further analyses proved the interannual wave climate variability in the TS is controlled predominantly by tropical cyclone activities in summer and by the northeasterly monsoon winds in winter. Furthermore, the interannual SWHA in the TS was found correlated highly negatively with the ENSO phenomenon. This relationship mainly derives from that during the northeasterly monsoon seasons. During the northeasterly monsoon seasons in El Ni?o(La Ni?a) years, the negative(positive) SWHA in the TS derives from weakened(strengthened) northeasterly monsoon winds induced by a lower-tropospheric anomalous anticyclone(cyclone) over the western Pacific Ocean and the South China Sea. During the southwesterly monsoon season in El Ni?o(La Ni?a) years, however, the SWH in the TS tends to increase(decrease) anomalously because of intensified(weakened) TC activities over the western North Pacific Ocean and adjacent seas.

Climate variability and predictability associated with the Indo-Pacific Oceanic Channel Dynamics in the CCSM4 Coupled System Model

An experiment using the Community Climate System Model(CCSM4), a participant of the Coupled Model Intercomparison Project phase-5(CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole(IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the "oceanic channel dynamics" and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.

Low-frequency variability of terrestrial water budget in China using GRACE satellite measurements from 2003 to 2010

Mass variations in terrestrial water storage（TWS） obtained from eight years of satellite data from the Gravity Recovery and Climate Experiment（GRACE） are used to describe low frequency TWS through Empirical Orthogonal Function（EOF） analysis. Results of the second seasonal EOF mode show the influence of the Meiyu season. Annual variability is clearly shown in the precipitation distribution over China, and two new patterns of interannual variability are presented for the first time from observations, where two periods of abrupt acceleration are seen in 2004 and 2008. GRACE successfully measures drought events in southern China, and in this respect, an association with the Arctic Oscillation and El Nino-Southern Oscillation is discussed. This study demonstrates the unique potential of satellite gravity measurements in monitoring TWS variations and large-scale severe drought in China.

Interannual variability in the sea surface cooling induced by tropical cyclones in the South China Sea

Sea surface cooling induced by tropical cyclones(TCs)is an important component of air-sea interactions.Using coordinate transformation and composite analysis methods,we examined the interannual variability in TCinduced sea surface cooling(TCSSC)in the South China Sea(SCS).The frequency of surface cooling cases was over 86%and that of surface warming cases was less than 14%.The magnitude of TCSSC was defined as the absolute value of TCSSC.The maximum magnitude of TCSSC occurred on the right side of the TC track,and the mean magnitude of TCSSC decreased by 0.04℃/a from 2006 to 2018.The interannual variability in TCSSC was highly correlated with the TC translation speed and pre-TC mixed layer depth.Notably,TCSSC got enhanced in El Nino years of 2007,2010,and 2015.The El Nino types were suggested to determine the occurring periods of strong TCSSC via controlling the positions of SCS anticyclones,which brought pre-TC shallow mixed layer and caused strong TCSSC via vertical mixing process during El Nino events.To quantify how the anticyclone influences TCSSC,we need to use mixed layer heat balances model in the next study.

AIR-SEA COUPLING FEATURES FROM THE WARM PHASE TO THE COLD PHASE OF ENSO CYCLES IN THE SEVENTIES TO THE EIGHTIES

Using the sea surface temperature and wind anomalies(SSTA and SSWA for short)of the tropical Pacific from January 1970 to December 1989,main spatial patterns of tropical Pacific SSTA and SSWA coupling features in the transform course from the warm phase to the cold phase of El Nino-southern Oscillation(ENSO)cycles are discussed. The main conclusions are as follows:(1)air-sea coupling patterns at the mature stage of El Nino(La Nina)are main spatial ones of tropical Pacific SSWA and SSTA coupling:(2)at the mature stage of El Nino,the interaction of the anticyclonic anomaly wind,generated by the forcing of distinct meridional SSTA gradient in the Northern Hemisphere tropical central Pacific.with the California cold current and SSTA is mainly responsible for weakening of El Nino;(3)the second sea temperature increase along the South American coast in the decaying course of El Nino results from the eastward movement of the weakened positive SSTA in the tropical central-eastern Pacific forced by anomalous west wind stress:(4)La Nina results from the joint effect of Walker circulation,Ekman drift and negative SSTA in the tropical central-eastern Pacific.

GFDL模式对太平洋海表面温度的年际和年代际变率的模拟评估

为评估美国地球物理流体动力学实验室(Geophysical Fluid Dynamics Laboratory,GFDL)模式CM3、ESM2M和ESM2G对太平洋海表面温度的年际和年代际变率的模拟能力,本文利用GFDL历史试验模拟结果和美国海洋大气局(National Oceanic and Atmospheric Administration,NOAA)提供的扩展重建的海表温度(Extended Reconstructed Sea Surface Temperature,ERSST)资料,比较模式模拟和观测的厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation,ENSO)和太平洋年代际振荡(Pacific Decadal Oscillation,PDO)的时空分布、周期及可预报性等。结果表明:三个模式均可以较好地模拟太平洋主要年际信号ENSO和年代际信号PDO,ESM2G对ENSO的模拟最好,CM3对PDO的模拟与观测更为接近。研究结果为进一步利用模式探讨ENSO和PDO的物理机制提供可能的参考。

吕宋和台湾岛以东黑潮季节与年际变化规律的对比分析

黑潮是北太平洋副热带环流系统的一支重要的西边界流。前人对不同流段黑潮的季节和年际变化进行了诸多研究,然而基于不同数据所得结论仍存在差异,尤其是不同模式计算所得流量差别很大,而且以往研究往往着眼于某一流段,对不同流段黑潮变化之间的异同及其原因涉及较少。本文基于卫星高度计数据,评估了OFES(Ocean generalcir culation model For the Earth Simulator)和HYCOM(Hybrid Coordinate Ocean Model)两个模式对吕宋岛和台湾岛以东黑潮季节与年际变化的模拟能力,进而对两个海域黑潮变化的异同及其物理机制进行了分析。结果表明:HYCOM模式对黑潮季节变化的模拟较好,而OFES模式对黑潮年际变化的模拟较好。吕宋岛以东黑潮和台湾岛以东黑潮在季节与年际尺度上的变化规律均不相同,且受不同动力过程控制。吕宋岛以东黑潮呈现冬春季强而秋季弱的变化规律,主要受北赤道流分叉南北移动的影响;而台湾岛以东黑潮呈现夏季强冬季弱的变化特点,主要受该海区反气旋涡与气旋涡相对数目的季节变化影响。在年际尺度上,吕宋岛以东黑潮与北赤道流分叉及风应力旋度呈负相关,当风应力旋度超前于流量4个月时相关系数达到了-0.56;而台湾岛以东黑潮的流量变化则受制于副热带逆流区涡动能的变化,且滞后于涡动能9个月时达到最大正相关,相关系数为0.44。本研究对于深入理解不同流段黑潮的多尺度变异规律及其对邻近海区环流与气候的影响具有重要意义,同时对于黑潮研究的数值模式选取具有重要参考价值。

Linkages Between Tropical Cyclones and Extreme Precipitation over China and the Role of ENSO

This research investigated the linkages between tropical cyclones(TCs)and extreme precipitation,and their associations with El Nino-Southern Oscillation(ENSO)over China.The contribution of TC-induced to total extreme precipitation events along the southeast coast of China was higher than 50%,and the values gradually decreased as TCs moved inland.However,the precipitation extremes(magnitude and frequency)related to TCs did not show statistically significant changes over the most recent 57 years.The impacts of TCs on precipitation extremes are evidently modulated by the ENSO phases.We found less extreme precipitation linked with TCs in southeastern China during El Nino phase,because of the fewer TC tracks over this region and less TC genesis in the western North Pacific(WNP).The small TC track density over southeastern China is due to the prevalent westerly steering flow and abnormal integrated vapor transport from northern to southern China during El Nino years.Additionally,warmer sea surface temperature,more vigorous westerlies,larger vorticity in 250 hPa,and higher divergence in 850 hPa in an El Nino phase jointly displaced the mean genesis of the WNP TCs eastward and this led to fewer TCs passing through southeastern China.

Spatial and Temporal Variability of Thermal Stress to China's Coral Reefs in South China Sea

Coral bleaching, caused by elevated sea surface temperature(SST), is occurring more frequently and seriously worldwide. Due to the lack of field observations, we understand little about the large-scale variability of thermal stress in the South China Sea(SCS) and its effect on China's coral reefs. This paper used 4-km high resolution gap-filled SST(Filled SST) data and thermal stress data related to coral bleaching derived from Coral Reef Temperature Anomaly Database(Co RTAD) to quantify the spatial and temporal characteristics of chronic thermal stress and acute thermal stress to China's coral reefs in SCS from 1982 to 2009. We analyzed the trend of SST in summer and the thermal stress frequency, intensity and duration during this period. The results indicate that, as a chronic thermal stress, summer mean SST in SCS shows an average upward trend of 0.2℃/decade and the spatial pattern is heterogeneous. Waters of Xisha Islands and Dongsha Islands of the northern SCS are warming faster through time compared to Zhongsha Islands and Nansha Islands sea areas of the southern SCS. High frequency bleaching related thermal stress events for these reefs are seen in the area to the northwest of Luzon Island. Severe anomaly thermal stress events are more likely to occur during the subsequent year of the El Nino year for these coral reefs. Besides, the duration of thermal stress varies considerably by anomaly year and by region.

The first two leading modes of the tropical Pacific and their linkage without global warming

A discrepancy remains in the first two leading empirical orthogonal function(EOF) modes of the tropical Pacific sea surface temperature anomaly(SSTA) based on observations since the 1980s. The EOF1 mode, representing the El Ni?o-Southern Oscillation(ENSO), is a robust result. However, the EOF2 features either El Ni?o Modoki(EM) or ENSO evolution during different periods, which is probably associated with the impacts of global warming. The underlying question is what the EOF2 mode of the tropical Pacific would be without global warming. Using the CMIP5 preindustrial scenario to exclude the influence of global warming, we find that the EOF1 mode of the tropical Pacific SSTA represents ENSO and that the EOF2 mode is not EM. According to the lead–lag correlation between the ENSO and EOF2 modes, the linkage between these two modes is as follows: …El Ni?o → EOF2 → La Ni?a →–EOF2 → El Ni?o…. By analyzing the evolution of sea surface temperature, surface wind, and subsurface ocean temperature anomalies, we find the mechanism linking the ENSO and EOF2 modes is the air–sea interaction associated with the ENSO cycle. This result suggests that the EOF2 mode represents an aspect of ENSO evolution under preindustrial conditions. Therefore, this study further indicates that the EM is probably due to the influence of global warming.

Exploring the reproductive ecology of the tropical semifossorial snake Ninia atrata

Based on histological analyses and field studies,this research describes the reproductive ecology of a population of Ninia atrata snakes inhabiting an oil palm plantation.Furthermore,through a multivariate approach,we explored the main drivers of reproductive output in N.atrata.Results showed that prey abundance and food intake were crucial variables contributing to reproductive output.Multiple linear regression models showed that neonates had high sensitivity(R2=55.29%)to extreme changes in climate,which was strongly related to slug and snail abundance variability and microhabitat quality.Reproductive cycles were markedly different between the sexes,being continuous in males and cyclical in females.Despite this variation,reproductive cycles at the population level were seasonal semi-synchronous.Constant recruitment of neonates all year,multiple clutches,high mating frequency,and continuous sperm production characterized the reproductive phenology of N.atrata.In addition,a significant number of previtellogenic females presented oviductal sperm as well as uterine scars,suggesting a high precocity in the species.The main drivers of reproductive output also differed between the sexes.In females,clutch size and secondary follicle variability were highly related to stomach bolus volume,fat body area,and body mass.In males,height of piles of palm leaves and body mass,rather than intrinsic reproductive traits,were the main drivers of sperm production.Nevertheless,in both cases,the relationship between body mass,prey abundance,and food intake suggests that N.atrata follows the income breeding strategy to compensate for reproductive costs and to maximize fitness.

Changes in lake area and water level in response to hydroclimate variations in the source area of the Yellow River:a case study from Lake Ngoring

In the north-eastern Qinghai-Tibet Plateau(QTP),the source area of the Yellow River(SAYR)has been experiencing significant changes in climatic and environmental conditions in recent decades.To date,few studies have combined modern hydrological conditions with paleoclimate records to explore the mechanism(s)of these changes.This study seeks to improve understanding of hydrological variability on decadal and centennial timescales in the SAYR and to identify its general cause.We first determined annual fluctuations in the surface area of Lake Ngoring from 1985 to 2020 using multi-temporal Landsat images.The results show that lake surface area changes were generally consistent with variations in precipitation,streamflow and the regional dry-wet index in the SAYR,suggesting that the water balance of the Lake Ngoring area is closely associated with regional hydroclimate changes.These records are also comparable to the stalagmite δ^(18)O monsoon record,as well fluctuations in the Southern Oscillation Index(SOI).Moreover,an association of high TSI(total solar insolation)anomalies and sunspot numbers with the expansion of Lake Ngoring surface area is observed,implying that solar activity is the key driving factor for hydrologic variability in the SAYR on a decadal timescale.Following this line of reasoning,we compared the δ^(13)C org-based lake level fluctuations of Lake Ngoring for the last millennium,as previously reported,with the hydroclimatic history and the reconstructed TSI record.We conclude that the hydrological regime of Lake Ngoring has been mainly controlled by centennial fluctuations in precipitation for the last millennium,which is also dominated by solar activity.In general,it appears that solar activity has exerted a dominant influence on the hydrological regime of the SAYR on both decadal and centennial timescales,which is clearly manifested in the variations of lake area and water level of Lake Ngoring.

Impact of ENSO on MJO Pattern Evolution over the Maritime Continent

The modulation of Madden–Julian oscillation(MJO)pattern evolution over the Maritime Continent(MC)by El Nino–Southern Oscillation(ENSO)was investigated through a combined observational and modeling study.MJO convective branches shifted south of the equator over the MC during eastern Pacific(EP)El Nino winters,while it became relatively symmetric about the equator during La Ni?a winters.The impact of central Pacific(CP)El Ninos to MJO pattern,on the other hand,is not statistically significant.The cause of the distinctive MJO pattern evolutions is likely attributed to the ENSO-induced changes of the background moisture and vertical shear over the MC.Idealized numerical experiments with a 2.5-layer model were carried out,and the result revealed that the background moisture change played a dominant role.An observational diagnosis of column-integrated moist static energy(MSE)budgets was further conducted.The result indicated that the MJO pattern difference was attributed to the MSE tendency asymmetry in front of MJO convection between EP El Nino and La Ni?a,caused by the advection of the mean MSE by anomalous meridional wind.The difference in the MJO-scale anomalous meridional wind was ultimately controlled by the change of the background meridional moisture gradient associated with EP El Nino and La Ni?a.

Effects of ENSO and Climate Change on Reference Evapotranspiration in Southern Vietnam

This study aims to evaluate the effects of climate change and El Nino-Southern Oscillation(ENSO)on reference evapotranspiration(ET_(o))in the climate sub-regions of South Vietnam(SVN)and the role of the related meteorological variables.The trend analysis shows that ET_(o) has been increasing quite clearly,especially during the rainy season.By examining the contribution of meteorological variables to the increase of ET_(o),it is indicated that temperature is the main contributor.Among the meteorological variables that are related to ET_(o),temperature is also the factor that has gained the most significant increase.Analysis of variance reveals that there is no difference in the increase of ET_(o) among the climate sub-regions of SVN.The effect of ENSO on ET_(o) is assessed based on the difference in the mean value of ET_(o) between the El Nino and La Nina phases.The results show that this difference is most obvious from October to May,and the main factor contributing to the increase is not temperature but sunshine hours.The difference in sunshine hours between the warm and cold phases in these months is around one hour per day,contributing about58%-86%to the ET_(o) difference.Further analysis of variance shows that ENSO has different levels of influences on ET_(o) in the climate sub-regions.Compared to the increase in ET_(o) due to climate change over the past 40 years,the ET_(o) difference between El Nino and La Nina phases is many times higher.In addition,since the effect of ENSO on ET_(o) is most obvious in the study area during the dry season,it is much stronger.In order to mitigate the effect of ENSO on drought in this area,monitoring and forecasting meteorological variables that have the main contribution to the variation of ET_(o),including the number of sunshine hours,should be promoted.

The variability of surface radiation fluxes over landfast sea ice near Zhongshan station,east Antarctica during austral spring

Surface radiative fluxes over landfast sea ice off Zhongshan station have been measured in austral spring for five springs between 2010 and 2015.Downward and upward solar radiation vary diurnally with maximum amplitudes of 473 and 290 W m^(−2),respectively.The maximum and minimum long-wave radiation values of the mean diurnal cycle are 218 and 210 W m^(−2)for downward radiation,277 and 259 W m^(−2)for upward radiation and 125 and−52 W m^(−2)for net radiation.The albedo has a U-shaped mean diurnal cycle with a minimum of 0.64 at noon.Sea ice thickness is in the growth phase for most spring days,but can be disturbed by synoptic processes.The surface temperature largely determines the occurrence of ice melting.Surface downward and upward long-wave radiation show synoptic oscillations with a 5–8 day period and intraseasonal variability with a 12–45 day period.The amplitudes of the diurnal,synoptic and intraseasonal variability show some differences during the five austral springs considered here.The intraseasonal and synoptic variability of downward and upward long-wave radiation are associated with the variability of cloud cover and surface temperature induced by the atmospheric circulation.

A Statistical Comparison of the Westerly Wind Bursts between the Positive and Negative Phases of the PDO

To understand the diversity of the El Ni?o–Southern Oscillation(ENSO)under the background of Pacific decadal oscillation(PDO)during recent decades,characteristics of westerly wind bursts(WWBs)during positive and negative phases of the PDO were analyzed.It is shown that,during the ENSO developing period,the El Ni?o evolution may be affected by stronger or more frequent WWBs in the positive PDO phase than in the negative PDO phase.The sustained effects of atmospheric dynamics on the equatorial ocean can be indicated by the accumulated WWB strength,which contains most WWB characteristics,including the accumulated days,occurrence frequency,strength,and spatial range of WWBs.The synoptic/climate systems that are directly related to WWBs show a wider spatial distribution in the positive PDO phase than in the negative PDO phase.

Summer Monsoon Rainfall Variability in Central China over the Past 4700 Years and Its Possible Link to Solar Activity

Based on 467 pairs ofδ^(18)O andδ^(13)C records and 8230 Th dates from a stalagmite(BF4)from Xiniu Cave,central China,we present a reconstruction of 9-yr resolution monsoon rainfall record for the past 4700 years.Ourδ^(18)O record shows good coherence with East Asian summer monsoon(EASM)rainfall proxies from adjacent regions during the overlapping intervals,suggesting thatδ^(18)O signal in BF4 can be interpreted as a monsoon rainfall proxy.Theδ^(13) C variations are related to changes in local processes at the cave site,and regional rainfall and temperature changes.Based on theδ18 O record,a series of dry periods can be identified at 4500-4200,3500-3200,2800-2500,1900-1600,1400-1200,700-500,and 400-200 yr BP,while a series of wet periods can be identified at 4200-3600,2400-2200,3200-2800,1100-900,600-400,and 200-100 yr BP.Power spectrum analysis on ourδ^(18) O record reveals significant cycles at 470 and 80 yr,coinciding with the typical solar periodic variations.This result suggests that changes in solar activity play a dominant role in driving centennial-decadal monsoon rainfall variation in central China.Due to minor changes in solar irradiance(less than 1.5 W m^(-2))over the past 4700 years,our record was further compared to the El Nino-Southern Oscillation(ENSO)and Pacific Decadal Oscillation(PDO)proxies,confirming that solar forcing on monsoon rainfall changes might be amplified by the ENSO and PDO variations.From 600 to 150 yr BP(the Little Ice Age,LIA),a positive shift of 2‰can be revealed in both theδ^(18)O andδ^(13)C records,indicating a cold/dry climatic pattern.By comparing ourδ^(18)O andδ^(13)C records with historical documents,we suggest that the climatic deteriorations between 450 and 250 yr BP may have caused serious social unrest at the end of the Ming Dynasty.