Robustness of Precipitation Projections in China:Comparison between CMIP5 and CMIP3 Models

Three sources of uncertainty in model projections of precipitation change in China for the 21st century were separated and quantified: internal variability,inter-model variability,and scenario uncertainty.Simulations from models involved in the third phase and the fifth phase of the Coupled Model Intercomparison Project(CMIP3 and CMIP5) were compared to identify improvements in the robustness of projections from the latest generation of models.No significant differences were found between CMIP3 and CMIP5 in terms of future precipitation projections over China,with the two datasets both showing future increases.The uncertainty can be attributed firstly to internal variability,and then to both inter-model and internal variability.Quantification analysis revealed that the uncertainty in CMIP5 models has increased by about 10%–60% with respect to CMIP3,despite significant improvements in the latest generation of models.The increase is mainly due to the increase of internal variability in the initial decades,and then mainly due to the increase of inter-model variability thereafter,especially by the end of this century.The change in scenario uncertainty shows no major role,but makes a negative contribution to begin with,and then an increase later.     

Uncertainty in Projection of Climate Extremes: A Comparison of CMIP5 and CMIP6

Climate projections by global climate models(GCMs) are subject to considerable and multi-source uncertainties.This study aims to compare the uncertainty in projection of precipitation and temperature extremes between Coupled Model Intercomparison Project(CMIP) phase 5(CMIP5) and phase 6(CMIP6), using 24 GCMs forced by 3 emission scenarios in each phase of CMIP. In this study, the total uncertainty(T) of climate projections is decomposed into the greenhouse gas emission scenario uncertainty(S, mean inter-scenario variance of the signals over all the models), GCM uncertainty(M, mean inter-model variance of signals over all emission scenarios), and internal climate variability uncertainty(V, variance in noises over all models, emission scenarios, and projection lead times); namely,T = S + M + V. The results of analysis demonstrate that the magnitudes of S, M, and T present similarly increasing trends over the 21 st century. The magnitudes of S, M, V, and T in CMIP6 are 0.94–0.96, 1.38–2.07, 1.04–1.69, and 1.20–1.93 times as high as those in CMIP5. Both CMIP5 and CMIP6 exhibit similar spatial variation patterns of uncertainties and similar ranks of contributions from different sources of uncertainties. The uncertainty for precipitation is lower in midlatitudes and parts of the equatorial region, but higher in low latitudes and the polar region. The uncertainty for temperature is higher over land areas than oceans, and higher in the Northern Hemisphere than the Southern Hemisphere. For precipitation, T is mainly determined by M and V in the early 21 st century, by M and S at the end of the 21 st century; and the turning point will appear in the 2070 s. For temperature, T is dominated by M in the early 21 st century, and by S at the end of the 21 st century, with the turning point occuring in the 2060 s. The relative contributions of S to T in CMIP6(12.5%–14.3% for precipitation and 31.6%–36.2% for temperature) are lower than those in CMIP5(15.1%–17.5% for precipitation and 38.6%–43.8% for temperature). By contrast, the relative contributions of M in CMIP6(50.6%–59.8% for precipitation and 59.4%–60.3% for temperature) are higher than those in CMIP5(47.5%–57.9% for precipitation and 51.7%–53.6% for temperature). The higher magnitude and relative contributions of M in CMIP6 indicate larger difference among projections of various GCMs. Therefore, more GCMs are needed to ensure the robustness of climate projections.     

Future Precipitation Extremes in China under Climate Change and Their Physical Quantification Based on a Regional Climate Model and CMIP5 Model Simulations

The atmospheric water holding capacity will increase with temperature according to Clausius-Clapeyron scaling and affects precipitation.The rates of change in future precipitation extremes are quantified with changes in surface air temperature.Precipitation extremes in China are determined for the 21st century in six simulations using a regional climate model,RegCM4,and 17 global climate models that participated in CMIP5.First,we assess the performance of the CMIP5 models and RCM runs in their simulation of extreme precipitation for the current period(RF:1982-2001).The CMIP5 models and RCM results can capture the spatial variations of precipitation extremes,as well as those based on observations:OBS and XPP.Precipitation extremes over four subregions in China are predicted to increase in the mid-future(MF:2039-58)and far-future(FF:2079-98)relative to those for the RF period based on both the CMIP5 ensemble mean and RCM ensemble mean.The secular trends in the extremes of the CMIP5 models are predicted to increase from 2008 to 2058,and the RCM results show higher interannual variability relative to that of the CMIP5 models.Then,we quantify the increasing rates of change in precipitation extremes in the MF and FF periods in the subregions of China with the changes in surface air temperature.Finally,based on the water vapor equation,changes in precipitation extremes in China for the MF and FF periods are found to correlate positively with changes in the atmospheric vertical wind multiplied by changes in surface specific humidity(significant at the p<0.1 level).     

CMIP6 Evaluation and Projection of Temperature and Precipitation over China

This article evaluates the performance of 20 Coupled Model Intercomparison Project phase 6(CMIP6)models in simulating temperature and precipitation over China through comparisons with gridded observation data for the period of 1995–2014,with a focus on spatial patterns and interannual variability.The evaluations show that the CMIP6 models perform well in reproducing the climatological spatial distribution of temperature and precipitation,with better performance for temperature than for precipitation.Their interannual variability can also be reasonably captured by most models,however,poor performance is noted regarding the interannual variability of winter precipitation.Based on the comprehensive performance for the above two factors,the“highest-ranked”models are selected as an ensemble(BMME).The BMME outperforms the ensemble of all models(AMME)in simulating annual and winter temperature and precipitation,particularly for those subregions with complex terrain but it shows little improvement for summer temperature and precipitation.The AMME and BMME projections indicate annual increases for both temperature and precipitation across China by the end of the 21st century,with larger increases under the scenario of the Shared Socioeconomic Pathway 5/Representative Concentration Pathway 8.5(SSP585)than under scenario of the Shared Socioeconomic Pathway 2/Representative Concentration Pathway 4.5(SSP245).The greatest increases of annual temperature are projected for higher latitudes and higher elevations and the largest percentage-based increases in annual precipitation are projected to occur in northern and western China,especially under SSP585.However,the BMME,which generally performs better in these regions,projects lower changes in annual temperature and larger variations in annual precipitation when compared to the AMME projections.     

How Large Precipitation Changes over Global Monsoon Regions by CMIP5 Models?

Future changes in precipitation over global monsoon domains and their adjacent dry regions are investigated using present-day climate simulations(1986–2005)and future climate simulations under the Representative Concentration Pathways(RCP4.5)scenario by the Coupled Model Intercomparison Project Phase 5(CMIP5)models.In the present-day climate simulations,high reproducibility of the extents of global monsoon domains and dry regions is observed from the multi-model ensemble(MME)result;the associated local summer precipitation variation and its interannual variability are also successfully reproduced.In the future,the global monsoon domains are projected to be expanded,while the dry regions are expected to initially increase and then decrease.The summer precipitation and its variability show significant increases over most global monsoon domains and obvious decreases over their adjacent dry regions.These results indicate that currently wet regions will become wetter and dry areas will be dryer under global warming conditions.Further analysis indicates that changes in summer precipitation over global monsoon and dry regions can be interpreted as moisture convergence changes associated with changes in horizontal moisture transport.     

How the “Best” Models Project the Future Precipitation Change in China

Projected changes in summer precipitation characteristics in China during the 21st century are assessed using the monthly precipitation outputs of the ensemble of three “best” models under the Special Report on Emissions Scenarios (SRES) A1B, A2, and B1 scenarios. The excellent reproducibility of the models both in spatial and temporal patterns for the precipitation in China makes the projected summer precipitation change more believable for the future 100 years. All the three scenarios experiments indicate a consistent enhancement of summer precipitation in China in the 21st century. However, the projected summer precipitation in China demonstrates large variability between sub-regions. The projected increase in precipitation in South China is significant and persistent, as well as in North China. Meanwhile, in the early period of the 21st century, the region of Northeast China is projected to be much drier than the present. But, this situation changes and the precipitation intensifies later, with a precipitation anomaly increase of 12.4%–20.4% at the end of the 21st century. The region of the Xinjiang Province probably undergoes a drying trend in the future 100 years, and is projected to decrease by 1.7%–3.6% at the end of the 21st century. There is no significant long-term change of the projected summer precipitation in the lower reaches of the Yangtze River valley. A high level of agreement of the ensemble of the regional precipitation change in some parts of China is found across scenarios but smaller changes are projected for the B1 scenario and slightly larger changes for the A2 scenario.     

Future changes and uncertainties in temperature and precipitation over China based on CMIP5 models

Climate changes in future 21 st century China and their uncertainties are evaluated based on 22 climate models from the Coupled Model Intercomparison Project Phase 5(CMIP5). By 2081–2100, the annual mean surface air temperature(SAT) is predicted to increase by 1.3℃± 0.7℃, 2.6℃± 0.8℃ and 5.2℃± 1.2℃ under the Representative Concentration Pathway(RCP) scenarios RCP2.6, RCP4.5 and RCP8.5, relative to 1986–2005, respectively. The future change in SAT averaged over China increases the most in autumn/winter and the least in spring, while the uncertainty shows little seasonal variation.Spatially, the annual and seasonal mean SAT both show a homogeneous warming pattern across China, with a warming rate increasing from southeastern China to the Tibetan Plateau and northern China, invariant with time and emissions scenario.The associated uncertainty in SAT decreases from northern to southern China. Meanwhile, by 2081–2100, the annual mean precipitation increases by 5% ± 5%, 8% ± 6% and 12% ± 8% under RCP2.6, RCP4.5 and RCP8.5, respectively. The national average precipitation anomaly percentage, largest in spring and smallest in winter, and its uncertainty, largest in winter and smallest in autumn, show visible seasonal variations. Although at a low confidence level, a homogeneous wetting pattern is projected across China on the annual mean scale, with a larger increasing percentage in northern China and a weak drying in southern China in the early 21 st century. The associated uncertainty is also generally larger in northern China and smaller in southwestern China. In addition, both SAT and precipitation usually show larger seasonal variability on the sub-regional scale compared with the national average.     

Projected Climate Change against Natural Internal Variability over China

The ability of 42 Coupled Model Intercomparison Project Phase 5(CMIP5) models in simulating the annual and seasonal temperature and precipitation over China is first examined by using their historical experiments for 1986–2005, and then 39 relatively reliable models are chosen to project temperature and precipitation changes against the natural internal variability over the country under the Representative Concentration Pathways(RCP) scenarios in the 21 st century. The result shows the temperature continuing to increase, especially in northern China. The annual warming for 2081–2099 relative to 1986–2005 over the whole of the country is larger than the background variability, with the multimodel median changes under RCP2.6, RCP4.5, RCP6.0, and RCP8.5 being 9.9, 19.3, 22.8, and 35.9 times greater than one standard deviation of internal variability, respectively. The annual precipitation is projected to increase by 6.1%, 9.3%, 9.6%, and 16.2% for 2081–2099 relative to 1986–2005 under RCP2.6, RCP4.5, RCP6.0, and RCP8.5 respectively, while large changes with high model agreement only occur over the northern Tibetan Plateau and Northeast China, which is mainly due to the robust changes in winter and spring under RCP6.0 and RCP8.5.     

Using Statistical Downscaling to Quantify the GCM-Related Uncertainty in Regional Climate Change Scenarios： A Case Study of Swedish Precipitation

There are a number of sources of uncertainty in regional climate change scenarios. When statistical downscaling is used to obtain regional climate change scenarios, the uncertainty may originate from the uncertainties in the global climate models used, the skill of the statistical model, and the forcing scenarios applied to the global climate model. The uncertainty associated with global climate models can be evaluated by examining the differences in the predictors and in the downscaled climate change scenarios based on a set of different global climate models. When standardized global climate model simulations such as the second phase of the Coupled Model Intercomparison Project （CMIP2） are used, the difference in the downscaled variables mainly reflects differences in the climate models and the natural variability in the simulated climates. It is proposed that the spread of the estimates can be taken as a measure of the uncertainty associated with global climate models. The proposed method is applied to the estimation of global-climate-model-related uncertainty in regional precipitation change scenarios in Sweden. Results from statistical downscaling based on 17 global climate models show that there is an overall increase in annual precipitation all over Sweden although a considerable spread of the changes in the precipitation exists. The general increase can be attributed to the increased large-scale precipitation and the enhanced westerly wind. The estimated uncertainty is nearly independent of region. However, there is a seasonal dependence. The estimates for winter show the highest level of confidence, while the estimates for summer show the least.     

Projected Changes in Asian Summer Monsoon in RCP Scenarios of CMIP5

Responses of the Asian Summer Monsoon(ASM) in future projections have been studied based on two core future projections of phase five of the Coupled Model Intercomparison Project(CMIP5) coordinated experiments with the IAP-coupled model FGOALS_s2(the Flexible Global Ocean-Atmosphere-Land System Model).The projected changes of the ASM in climatological mean and interannual variability were respectively reported.Both the South Asian Summer Monsoon(SASM) and the East Asian Summer Monsoon(EASM) were intensified in their climatology,featuring increased monsoon precipitation and an enhanced monsoon lower-level westerly jet flow.Accordingly,the amplitude of the annual cycle of rainfall over East Asia(EA) is enhanced,thereby indicating a more abrupt monsoon onset.After the EA monsoon onset,the EASM marched farther northward in the future scenarios than in the historical runs.In the interannual variability,the leading pattern of the EASM,defined by the first multi-variable EOF analysis over EA,explains more of the total variances in the warmest future scenario,specifically,Representative Concentration Pathway(RCP8.5).Also,the correlation coefficients analysis suggests that the relationship between the EASM interannual variations and ENSO was significantly strengthened in the future projections,which may indicate improved predictability of the EASM interannual variations.     

Projections of the East Asian Winter Monsoon under the IPCC AR5 Scenarios Using a Coupled Model: IAP-FGOALS

Responses of the East Asian winter monsoon(EAWM) in future projections were studied based on two core future projections of CMIP5 in coordinated experiments with the IAP-coupled model FGOALS2-s.The projected changes of EAWM in climatology,seasonality,and interannual variability are reported here;the projections indicated strong warming in winter season.Warming increased with latitude,ranging from 1 C to 3 C in the Representative Concentration Pathways simulation RCP4.5 projection(an experiment that results in additional radiative forcing of ～4.5 W m 2 in 2100) and from 4 C to 9 C in the RCP8.5 projection(an experiment that results in additional radiative forcing of ～8.5 W m 2 in 2100).The northerly wind along the East Asian coastal region became stronger in both scenarios,indicating a stronger EAWM.Accordingly,interannual variability(described by the standard deviation of temperature) increased around the South China Sea and lower latitudes and decreased over eastern China,especially in North China.The two EAWM basic modes,defined by the temperature EOF analysis over East Asia,were associated with the Arctic Oscillation(AO) and stratospheric polar vortex.The future projections revealed more total variance attributable to the secondary mode,suggesting additional influences from the stratosphere.The correlation between AO and the leading mode decreased,while the correlation between AO and the secondary mode increased,implying increased complexity regarding the predictability of EAWM interannual variations in future projections.     

Climate Simulation and Future Projection of Precipitation and the Water Vapor Budget in the Haihe River Basin

The climatological characteristics of precipitation and the water vapor budget in the Haihe River basin (HRB) are analyzed using daily observations at 740 stations in China in 1951-2007 and the 4-time daily ERA40 reanalysis data in 1958-2001. The results show that precipitation and surface air temperature present significant interannual and interdecadal variability, with cold and wet conditions before the 1970s but warm and dry conditions after the 1980s. Precipitation has reduced substantially since the 1990s, with a continued increase of surface air temperature. The total column water vapor has also reduced remarkably since the late 1970s. The multi-model ensemble from the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) has capably simulated the 20th century climate features and successfully reproduced the spatial patterns of precipitation and temperature. Unfortunately, the models do not reproduce the interdecadal changes. Based on these results, future projections of the climate in the HRB are discussed under the IPCC Special Report on Emissions Scenarios (SRES) B1, A1B, and A2. The results show that precipitation is expected to increase in the 21st century, with substantial interannual fluctuations relative to the models’ baseline climatology. A weak increasing trend in precipitation is projected before the 2040s, followed by an abrupt increase after the 2040s, especially in winter. Precipitation is projected to increase by 10%-18% by the end of the 21st century. Due to the persistent warming of surface air temperature, water vapor content in the lower troposphere is projected to increase. Relative humidity will decrease in the mid-lower troposphere but increase in the upper troposphere. On the other hand, precipitation minus evaporation remains positive throughout the 21st century. Based on these projection results, the HRB region is expected to get wetter in the 21st century due to global warming.     

Surface Temperature Changes Projected by FGOALS Models under Low Warming Scenarios in CMIP5 and CMIP6

To meet the low warming targets proposed in the 2015 Paris Agreement,substantial reduction in carbon emissions is needed in the future.It is important to know how surface climates respond under low warming targets.The present study investigates the surface temperature changes under the low-forcing scenario of Representative Concentration Pathways(RCP2.6)and its updated version(Shared Socioeconomic Pathways,SSP1-2.6)by the Flexible Global Ocean-Atmosphere-Land System(FGOALS)models participating in phases 5 and 6 of the Coupled Model Intercomparison Project(CMIP5 and CMIP6,respectively).In both scenarios,radiative forcing(RF)first increases to a peak of 3 W m^?2 around 2045 and then decreases to 2.6 W m^?2 by 2100.Global mean surface air temperature rises in all FGOALS models when RF increases(RF increasing stage)and declines or holds nearly constant when RF decreases(RF decreasing stage).The surface temperature change is distinct in its sign and magnitude between the RF increasing and decreasing stages over the land,Arctic,North Atlantic subpolar region,and Southern Ocean.Besides,the regional surface temperature change pattern displays pronounced model-to-model spread during both the RF increasing and decreasing stages,mainly due to large intermodel differences in climatological surface temperature,ice-albedo feedback,natural variability,and Atlantic Meridional Overturning Circulation change.The pattern of tropical precipitation change is generally anchored by the spatial variations of relative surface temperature change(deviations from the tropical mean value)in the FGOALS models.Moreover,the projected changes in the updated FGOALS models are closer to the multi-model ensemble mean results than their predecessors,suggesting that there are noticeable improvements in the future projections of FGOALS models from CMIP5 to CMIP6.     

Preface to the Special Issue:Aerosols,Clouds,Radiation,Precipitation,and Their Interactions

正The treatment of aerosols,clouds,radiation,and precipitation in climate models,in addition to their interactions and associated feedbacks,has long been one of the largest sources of uncertainty in predicting any potential future climate changes.Although many improvements have been made in CMIP5,aerosols,clouds,radiation,and their feedbacks are still a problem     

Asian summer monsoon onset in simulations and CMIP5 projections using four Chinese climate models

The reproducibility and future changes of the onset of the Asian summer monsoon were analyzed based on the simulations and projections under the Representative Concentration Pathways(RCP) scenario in which anthropogenic emissions continue to rise throughout the 21 st century(i.e. RCP8.5) by all realizations from four Chinese models that participated in the Coupled Model Intercomparison Project Phase 5(CMIP5). Delayed onset of the monsoon over the Arabian Sea was evident in all simulations for present-day climate, which was associated with a too weak simulation of the low-level Somali jet in May.A consistent advanced onset of the monsoon was found only over the Arabian Sea in the projections, where the advanced onset of the monsoon was accompanied by an increase of rainfall and an anomalous anticyclone over the northern Indian Ocean. In all the models except FGOALS-g2, the enhanced low-level Somali jet transported more water vapor to the Arabian Sea, whereas in FGOALS-g2 the enhanced rainfall was determined more by the increased wind convergence. Furthermore,and again in all models except FGOALS-g2, the equatorial SST warming, with maximum increase over the eastern Pacific,enhanced convection in the central West Pacific and reduced convection over the eastern Indian Ocean and Maritime Continent region, which drove the anomalous anticyclonic circulation over the western Indian Ocean. In contrast, in FGOALS-g2, there was minimal(near-zero) warming of projected SST in the central equatorial Pacific, with decreased convection in the central West Pacific and enhanced convection over the Maritime Continent. The broader-scale differences among the models across the Pacific were related to both the differences in the projected SST pattern and in the present-day simulations.     

Statistical Downscaling of FGOALS-s2 Projected Precipitation in Eastern China

A statistical regression downscaling method was used to project future changes in precipitation over eastern China based on Phase 5 of the Coupled Model Intercomparison Project （CMIPS） the Representative Concentration Pathway （RCP） scenarios simulated by the second spectral version of the Flexible Global Ocean- Atmosphere-Land System （FGOALS-s2） model. Our val- idation results show that the downscaled time series agree well with the present observed precipitation in terms of both the annual mean and the seasonal cycle. The regres- sion models built from the historical data are then used to generate future projections. The results show that the en- hanced land-sea thermal contrast strengthens both the subtropical anticyclone over the western Pacific and the east Asian summer monsoon flow under both RCPs. However, the trend of precipitation in response to warming over the 21 st century are different across eastern Chi- na under different RCPs. The area to the north of 32°N is likely to experience an increase in annual mean precipitation, while for the area between 23°N and 32°N mean precipitation is projected to decrease slightly over this century under RCP8.5. The change difference between scenarios mainly exists in the middle and late century. The land-sea thermal contrast and the associated east Asian summer monsoon flow are stronger, such that precipitation increases more, at higher latitudes under RCP8.5 compared to under RCP4.5. For the region south of 32°N, rainfall is projected to increase slightly under RCP4.5 but decrease under RCP8.5 in the late century. At the high resolution of 5 km, our statistically downscaled results for projected precipitation can be used to force hydrological models to project hydrological processes, which will be of great benefit to regional water planning and management.     

Projection of Summer Precipitation over the Yangtze–Huaihe River Basin Using Multimodel Statistical Downscaling Based on Canonical Correlation Analysis

By using observational daily precipitation data over the Yangtze–Huaihe River basin, ERA-40 data, and the data from eight CMIP5 climate models, statistical downscaling models are constructed based on BP-CCA(combination of empirical orthogonal function and canonical correlation analysis) to project future changes of precipitation. The results show that the absolute values of domain-averaged precipitation relative errors of most models are reduced from 8%–46% to 1%–7% after statistical downscaling. The spatial correlations are all improved from less than 0.40 to more than 0.60. As a result of the statistical downscaling multimodel ensemble(SDMME), the relative error is improved from –15.8% to –1.3%, and the spatial correlation increases significantly from 0.46 to 0.88. These results demonstrate that the simulation skill of SDMME is relatively better than that of the multimodel ensemble(MME) and the downscaling of most individual models. The projections of SDMME reveal that under the RCP(Representative Concentration Pathway)4.5 scenario, the projected domain-averaged precipitation changes for the early(2016–2035), middle(2046–2065), and late(2081–2100) 21 st century are –1.8%, 6.1%, and 9.9%, respectively. For the early period, the increasing trends of precipitation in the western region are relatively weak, while the precipitation in the east shows a decreasing trend. Furthermore, the reliability of the projected changes over the area east of115?E is higher than that in the west. The stations with significant increasing trends are primarily located over the western region in both the middle and late periods, with larger magnitude for the latter. Stations with high reliability mainly appear in the region north of 28.5?N for both periods.     

Differences between CMIP6 and CMIP5 Models in Simulating Climate over China and the East Asian Monsoon

We compare the ability of coupled global climate models from the phases 5 and 6 of the Coupled Model Intercomparison Project(CMIP5 and CMIP6, respectively) in simulating the temperature and precipitation climatology and interannual variability over China for the period 1961–2005 and the climatological East Asian monsoon for the period1979–2005. All 92 models are able to simulate the geographical distribution of the above variables reasonably well.Compared with earlier CMIP5 models, current CMIP6 models have nationally weaker cold biases, a similar nationwide overestimation of precipitation and a weaker underestimation of the southeast–northwest precipitation gradient, a comparable overestimation of the spatial variability of the interannual variability, and a similar underestimation of the strength of winter monsoon over northern Asia. Pairwise comparison indicates that models have improved from CMIP5 to CMIP6 for climatological temperature and precipitation and winter monsoon but display little improvement for the interannual temperature and precipitation variability and summer monsoon. The ability of models relates to their horizontal resolutions in certain aspects. Both the multi-model arithmetic mean and median display similar skills and outperform most of the individual models in all considered aspects.     

The Projection of Temperature and Precipitation over China under RCP Scenarios using a CMIP5 Multi-Model Ensemble

Climate changes in 21st century China are described based on the projections of 11 climate models under Representative Concentration Pathway (RCP) scenarios. The results show that warming is expected in all regions of China under the RCP scenarios, with the northern regions showing greater warming than the southern regions. The warming tendency from 2011 to 2100 is 0.06°C/10 a for RCP2.6, 0.24°C/10 a for RCP4.5, and 0.63°C/10 a for RCP8.5. The projected time series of annual temperature have similar variation tendencies as the new greenhouse gas (GHG) emission scenario pathways, and the warming under the lower emission scenarios is less than under the higher emission scenarios. The regional averaged precipitation will increase, and the increasing precipitation in the northern regions is significant and greater than in the southern regions in China. It is noted that precipitation will tend to decrease in the southern parts of China during the period of 2011-2040, especially under RCP8.5. Compared with the changes over the globe and some previous projections, the increased warming and precipitation over China is more remarkable under the higher emission scenarios. The uncertainties in the projection are unavoidable, and further analyses are necessary to develop a better understanding of the future changes over the region.     

Evaluation of spring persistent rainfall over East Asia in CMIP3/CMIP5 AGCM simulations

The progress made fi＇om Phase 3 to Phase 5 of the Coupled Model Intercomparison Project （CMIP3 to CMIP5） in simulating spring persistent rainfall （SPR） over East Asia was examined from the outputs of nine atmospheric general circulation models （AGCMs）. The majority of the models overestimated the precipitation over the SPR domain, with the mean latitude of the SPR belt shifting to the north. The overestimation was about 1mm d-1 in the CMIP3 ensemble, and the northward displacement was about 3°, while in the CMIP5 ensemble the overestimation was suppressed to 0.7 mm d-i and the northward shift decreased to 2.5°. The SPR features a northeast-southwest extended rain belt with a slope of 0.4°N/°E. The CMIP5 ensemble yielded a smaller slope （0.2°N/°E）, whereas the CMIP3 ensemble featured an unre- alistic zonally-distributed slope. The CMIP5 models also showed better skill in simulating the interannual variability of SPR. Previous studies have suggested that the zonal land-sea thermal contrast and sensible heat flux over the southeastern Tibetan Plateau are important for the existence of SPR. These two ther- mal factors were captured well in the CMIP5 ensemble, but underestimated in the CMIP3 ensemble. The variability of zonal land-sea thermal contrast is positively correlated with the rainfall amount over the main SPR center, but it was found that an overestimated thermal contrast between East Asia and South China Sea is a common problem in most of the CMIP3 and CMIP5 models. Simulation of the meridional thermal contrast is therefore important for the future improvement of current AGCMs.