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In order to evaluate the predictive simulation ability of the CMA-CPSv3 climate prediction model （hereafter CMA-CPSv3 model） on two high-pressure systems， the South Asian High and the Western Pacific Subtropical High， that affect summer precipitation in China， the return simulated data by the CMA-CPSv3 model starting in March and May from 2001 to 2020 and ERA5 reanalysis data were used to firstly evaluate the model’s predictive ability on the characteristic indices of the two high-pressure systems， and then analyze the predictive ability of the differences in predicting the summer circulation system and water vapor characteristics between two high-pressure systems in the same good year and the same bad year， as well as their impact on summer precipitation in China， were compared.The possible reasons for the stronger prediction of the two high-pressure systems were explored.The main conclusions were as follows： （1） The CMA-CPSv3 model has the best prediction effect on the average ridge position of the West Pacific subtropical high and the South Asian high， with the predicted results of the intensity index and area index being significantly stronger or larger； Compared with the forecast starting in March， the forecast results starting in May have a certain improvement in the prediction of the West Pacific subtropical high.（2） The CMA-CPSv3 model has well predicted the circulation situation at 100 hPa and 500 hPa， with good predictions for temperature and wind fields.However， the predicted range of the South Asian High and the West Pacific Subtropical High is generally stronger.（3） The predicted positions of the ridge line of the two high-pressure systems in the same good year and the same poor year are relatively good， and the predicted areas and intensities are significantly stronger.The prediction deviation for the same good year is relatively small.It can better predict the spatial distribution of water vapor flux in East Asia and the distribution pattern of summer precipitation in China.（4） The upward motion of the predicted two high pressure systems in the longitude region is weaker than the ERA5 result， which may be one of the reasons for the larger range and stronger intensity of the predicted South Asian High and West Pacific Subtropical High.

Surface heat source (SHS) is a crucial factor affecting local weather systems. Particularly SHS on the Tibetan Plateau (TP) significantly influences East Asian atmospheric circulation and global climate. Accurate prediction of summer SHS on the TP is of urgent demand for economic development and local climate change. To evaluate the performance of SHS on the TP, the observed SHS data from the eleven sites on the TP verified against CRA40-land (CRA) is evidenced significantly better than ERA5-land (ERA5), another widely used reanalysis. The predictive capability of the CMA Climate Prediction System Model (CMA-CPS) for SHS on the TP was assessed using multiple scoring methods, including the anomaly correlation coefficient and temporal correlation coefficient, among others. Furthermore, relative variability and trend analysis were conducted. Finally, based on these assessments, the causes of the biases were preliminarily discussed. The CMA-CPS demonstrates a reasonable ability to predict the spatial distribution patterns of SHS, sensible heat (SH), and latent heat (LH) on the TP in summer. Specifically, the prediction results of SHS and LH exhibit an “east-high and west-low” distribution, while the distribution of the predicted SH is opposite. Nevertheless, the predicted values are generally lower than CRA, particularly in interannual variations and trends. Among the predictions, LH exhibits the highest temporal correlation coefficients, consistently above 0.6, followed by SHS, while SH predictions are less accurate. The spatial distribution and skill scores indicate that LH on the TP contributes more significantly to SHS than SH in summer. Furthermore, discrepancies in the predictions of surface temperature gradients, ground wind speed, and humidity on the TP may partly explain the biases in SHS and their components.

In order to explore the role of the changes in the strength and weakness of the South Asian monsoon on the vertical circulation of the Qinghai-Xizang （Tibetan） Plateau， the South Asian monsoon index WYI was calculated using the high-resolution JRA55 reanalysis data for the past 30 years from 1990 to 2019 and the strong and weak years of the South Asian monsoon were selected， and the effects of the changes in the strength and weakness of the South Asian monsoon on the vertical circulation of the Qinghai-Xizang （Tibetan） Plateau were analyzed by comparing the three different periods of the pre-monsoon outbreak， outbreak period and late outbreak.The following main conclusions were obtained： （1） The strength and extent of updrafts on the southern side of the plateau in May in WYI strong years are greater than in weak years， the intensity of updrafts on the main and southern sides of the plateau increases in July， and the difference between strong and weak years is not obvious.（2） In May and October， both mass and energy converge to the plateau from the south and north sides of the plateau， while in July， it turns to dissipate mass and energy from the plateau to the north and south sides.the intensity of the upper-level radiation dispersion in the south side of the plateau in the WYI strong year is greater than that in the weak year， and the difference of the irradiation intensity in the lower level is smaller.The difference in the intensity of energy and mass transfer between WYI strong and weak years is greatest in May and least in July.（3） In the WYI strong year， the 100 hPa South Asian high pressure shifts to the western type in October， and the 500 hPa West Pacific subalpine lifts northward， so the wind field on the southern side of the plateau shifts and raises the high altitude temperature， while in the WYI weak year this phenomenon occurs in May， indicating that the South Asian monsoon changes the horizontal circulation situation at high altitude and thus affects the vertical circulation of the plateau.The surface temperature of the main body of the plateau in May， July and October in WYI strong years is greater than that in weak years， indicating that under the influence of the warm and humid airflow brought by the South Asian monsoon， the updraft from the southern side of the plateau lifts to the plateau， and the surface temperature of the plateau increases significantly， and the surface heat of the plateau increases which in turn affects the vertical circulation of the plateau.

Based on the knowledge that the main sources of summer water vapor on the Qinghai-Xizang （Tibet） Plateau are the Arabian Sea， the Bay of Bengal， and the South China Sea， a simulation study of the effects of different water vapor sources on the eastern-type and western-type precipitation on the Qinghai-Xizang （Tibet） Plateau in summer was carried out.Numerical simulations of water vapor content reduction at different water vapor source locations were conducted using conventional observations， NCEP/NCAR global reanalysis data， and the mesoscale numerical model WRF for two intense precipitation processes on the Qinghai-Xizang （Tibet） Plateau from June 28 to July 2， 2016 （eastern type） and from July 19 to 23， 2018 （western type）， by separately integrating the Arabian Sea， Bay of Bengal， and South China Sea By comparing three sets of sensitivity experiment and control experiment， the relative humidity at the Arabian Sea， the Bay of Bengal and the South China Sea was reduced by 70%， 60%， 50%， 40% and 30% from the ground to 100hPa respectively， and the effects of the reduction of water vapor content at different water vapor sources on summer precipitation on the plateau were explored in depth from the perspectives of circulation field， water vapor transport and precipitation changes， and the following main conclusions were obtained： （1） The reduction of water vapor content at three water vapor sources has an effect on The reduction of water vapor over the Bay of Bengal significantly reduced the summer precipitation of the Qinghai-Xizang （Tibet） Plateau by about 10% in 2016 （eastern type） and 2018 （western type） compared with the controlled experiment， while the reduction of water vapor over the South China Sea had minimal effects on the two summer precipitation processes of the Qinghai-Xizang （Tibet） Plateau.Reducing the water vapor over the Arabian Sea plays a catalytic role in the precipitation of the western type of the plateau， increasing the precipitation by about 10% relative to the controlled test； and inhibiting the precipitation of the eastern type of the plateau， making the precipitation decrease by about 5% relative to the controlled test.（2） Changing the water vapor conditions over the Bay of Bengal source has the most obvious effect on the precipitation on the Qinghai-Xizang （Tibet） Plateau.The possible reason is that reducing the water vapor conditions over the Bay of Bengal makes the low value system on the southern side of the plateau weaken， and the southerly wind on the plateau weakens， resulting in weaker water vapor transport， resulting in less precipitation on the plateau.（3） The difference of water vapor revenue and expenditure in the plateau region was not obvious in the control experiment and three sensitivity experiment at the beginning of the simulation， but with the increase of simulation time （after about 48 h）， there were obvious differences in water vapor revenue and expenditure in the Qinghai-Xizang （Tibet） Plateau， and there was an obvious correlation between water vapor revenue and expenditure and daily precipitation.

In order to study the characteristics of low frequency oscillation of summer precipitation over Qinghai-Xizang Plateau， based on the daily precipitation data of 62 meteorological stations over the Qinghai-Xizang Plateau from 1978 to 2017 and the high-resolution daily reanalysis data of ERA5.This paper adopted the collection of empirical mode decomposition （EEMD）， Lanczos filter and synthesis analysis method.Filter out the years of drought and flood， and analyzed the characteristics of low frequency oscillation， variation of meteorological elements and circulation of precipitation in dry and flood years in summer over the Qinghai-Xizang Plateau.Reveals the drought and flood years， the characteristics of low frequency oscillation period of precipitation in plateau area， the circulation characteristics and low frequency and other transmission characteristics of wind field and vorticity field.The results show that： （1） There is an oscillation period of 10~20 days in summer precipitation over the Qinghai-Xizang Plateau.The period frequency of drought and flood years is different， the oscillation frequency of flood years is obviously higher than that of drought years.In flood years， the significant oscillation is 10~20 days and 30-days oscillation， while in drought years， the oscillation is mainly 10~20 days.（2） In flood years， the low-frequency precipitation phase is strong， the high-altitude low-frequency cyclones control the plateau， the high-altitude divergence， the low-altitude convergence.The water vapor supply from the south of the Bay of Bengal， and the low-frequency disturbance is strong， which is conducive to the occurrence of precipitation， there is an abnormal circulation distribution of low-frequency anticyclone- low-frequency cyclone- low-frequency anticyclone from west to east.On the contrary， in the low frequency precipitation weak phase， the high frequency anticyclone controlled the main body of the plateau， high altitude convergence， low altitude divergence， the warm and wet southerly air is weak， the disturbance is weak， not conducive to the occurrence of precipitation.The distribution of low-frequency anticyclone， low-frequency cyclones and low-frequency anticyclone is not obvious in drought years， and the oscillation intensity is not as strong as that in flood years， and the intensity of low-frequency element field is weak.（3） The transmission of low-frequency fluctuation is different in drought and flood years.In flood years， the high and low plateau is the sink area of low-frequency oscillation， and the meridian is also the convergence area.The precipitation in the oscillation sink area is more frequent， so the precipitation in flood years is more.In the dry years， the low-frequency oscillation propagates upward from the plateau to the upper level， so the low-frequency precipitation occurs less in the dry years.

Roots play an important role in the carbon cycle of ecosystems.The Earth System Models （ESMs） of the Coupled Model Intercomparison Project （CMIP） have been widely used to simulate and predict root biomass.In this paper， the spatial distribution， dynamic change， and comparison with observed values of root biomass of 14 ESMs simulated historical experiments were analyzed.The results showed that： （1） The global distribution of multi-year average from 1850 to 2005 of root biomass indicated that 7 ESMs had maximum or minimum values， while the rest ESMs showed that root biomass was higher in the middle and high latitudes of the equator and the northern hemisphere.The root biomass distribution at different latitudes showed that 40°S is also one of the high value areas； （2） The simulation results from 1995 to 2005 are compared with the site observation data （1990 -2010） in different climatic zones by using SS index， the result showed deviations are relatively large but the simulation effect of temperate zone is slightly better than frigid zone and tropical zone.On the global scale， BCC-CSM2-MR is the best simulated ESM； （3） In the Qinghai-Xizang Plateau， ESMs can reasonably simulate the seasonal variation over the years 1850 to 2005 of root biomass， but the relationship between interannual variation of the simulated root biomass and the meteorological factors （temperature， precipitation） by different ESMs is different.In order to conduct more precise and in-depth research and analysis， in addition to improving the model， it is also necessary to improve the collection of observational data.

In order to further study the characteristic indices and their interactive function based on ERA5 reanalysis data from the European Centre for Medium-term Weather Forecasts （ECMWF） from 2001 to 2020 with the horizontal resolution of 0.25°×0.25°， the intensity index， area index， ridge position and east-west extension ridge point of the South Asian High （SAH） and the West Pacific Subtropical High （WPSH） are calculated in summer by statistical methods.And the distance of the relative position of the longitude and latitude and the same strong and weak years in summer are selected.The influence of their cooperation on the summer precipitation in eastern China is studied by the comparative analysis.The results show as follow： （1） There is a good positive correlation between the intensity index and the area index of the SAH and the WPSH in summer.The pentad changes of the ridgeline position of the SAH is very well related to changes in its intensity and area indices.Better consistency， the more north （south） the SAH deviates， the larger （smaller） its intensity and area are.（2） The changes in pentad of the east-west ridge point between the WPSH and the SAH have a trend of "going towards each other and going away from each other".Under the temporal changes， the sudden change of the zonal position of the SAH is later than that of the meridional position.The interval time of the sudden change is about 4 pentads/20 days.（3） When the SAH and the WPSH are both strong （weak）， the rainfall in the middle and lower reaches of the Yangtze River is much （less）， and the rainfall in South China is less （much）.When their latitudes and longitudes are abnormally close， there is less precipitation in the overlapping area， more precipitation on the northern side of the overlapping area， and the precipitation band is generally zonal.The area from the lower reaches of the Yellow River to the sea estuary has more precipitation， and the precipitation in the south of the Yangtze River and South China less.When their latitude and longitude directions are abnormally far apart， there is more precipitation in South China， and less precipitation in the middle and lower reaches of the Yangtze River.

The BCC-CSM2 model is the second generation of the Beijing Climate Center Climate System Model developed by the National Center of China Meteorological Administration. Using the outputs of two versions of the BCC-CSM2 model with different resolutions, namely: BCC-CSM2-MR and BCC-CSM2-HR, their performance in simulating the climate characteristics of Northwest China was compared. The BCC-CSM2-HR had a better ability to simulate the detailed distribution of the average temperature and precipitation in Northwest China, and could delineate the influence of the topography in detail. The extreme events in Northwest China were evaluated further using the BCC-CSM2-HR and the observation data from China Meteorological Data Center. The BCC-CSM2-HR provided a good simulation of the spatial distribution of extreme climate events in Northwest China, and the spatial distribution of TXx, TNx, TXn, and TNn in Northwest China show closer proximity to the observation than that of TX90p, TN90p, TX10p, and TN10p, even in the case of extreme heavy precipitation. This case study of the extreme weather events showed that the BCC-CSM2-HR model had the best simulation performance for extreme high temperature events in Northwest China, followed by extreme low temperature events, and had the worst simulation ability for extreme precipitation events.

The cold tongue mode (CTM), which represents the out-of-phase relationship in sea surface temperature anomaly (SSTA) variability between the Pacific cold tongue region and elsewhere in the tropical Pacific, shows a long-term cooling trend in the eastern equatorial Pacific. In this study, we investigate how well the CTM is reproduced in historical simulations generated by the 20 models considered in Phase 5 of the Coupled Model Intercomparison Project (CMIP5). Qualitatively, all 20 models roughly capture the cooling SSTA associated with the CTM. However, a quantitative assessment (i.e., Taylor diagrams and the ratio of the trend between the simulations and observations) shows that only five of these 20 models (i.e., CESM1-CAM5, CMCC-CM, FGOALS-g2, IPSL-CM5B-LR, and NorESM1-M) can reproduce with useful accuracy the spatial pattern and long-term trend of the CTM. We find that these five models generally simulate the main ocean dynamical process associated with the CTM. That is, these models adequately capture the long-term cooling trend in the vertical advection of the anomalous temperature by the mean upwelling. We conclude that the performance of these CMIP5 models, with respect to simulations of the long-term cooling trend associated with the vertical advection, and the related long-term decreasing trend of the vertical gradient of the oceanic temperature anomaly, can play an important role in successful reproduction of the CTM.

Abstract Extreme precipitation over drylands, especially deserts, has been observed, whereas the precipitation changes in Chinese deserts have been rarely studied. Here, we used a daily grid precipitation data set generated via weather station data (0.25° horizontal grid spacing) to investigate the spatial and temporal changes in extreme precipitation in Chinese deserts. Extreme precipitation based on the changes in the total precipitation (PRCPTOT) and the annual maximum daily precipitation (Rx1day) in the Chinese desert exhibited markedly increasing trends and presented a spatial distribution of wetting in the western deserts and drying in the eastern deserts. The increase in extreme precipitation could minimize wind erosion and intensify dune stabilization in the western Chinese deserts.

Through analyzing the changes of averaged temperature and precipitation along the Brahmaputra Valley from 1980 to 2005, and investigating the correlation between atmospheric circulation indices and these changes, the respondence of the Brahmaputra Valley to the global warming had been analyzed in this paper. It is found that the Brahmaputra Valley climate became warmer and wetter from 1980 to 2005, and the change magnitude is higher than that over the whole Tibetan Plateau. Therefore, the respondence of the Brahmaputra valley to the global warming is more evident than that of the whole plateau during the period. The relationship between atmospheric circulation indices and the regional climate change is significant. When North Atlantic Oscillation index is higher in summer, the climate of the Brahmaputra Valley becomes warmer and dryer; vice versa. When South Oscillation index is higher, it becomes warmer and wetter; vice versa.Worthy of note, the results in this study only emphasize some evidence of change in temperature and precipitation over the Brahmaputra Valley during 1980-2005. [ABSTRACT FROM AUTHOR]