CAS-ESM2.0 Model Datasets for the CMIP6 Ocean Model Intercomparison Project Phase 1 (OMIP1)

As a member of the Chinese modeling groups,the coupled ocean-ice component of the Chinese Academy of Sciences’Earth System Model,version 2.0(CAS-ESM2.0),is taking part in the Ocean Model Intercomparison Project Phase 1(OMIP1)experiment of phase 6 of the Coupled Model Intercomparison Project(CMIP6).The simulation was conducted,and monthly outputs have been published on the ESGF(Earth System Grid Federation)data server.In this paper,the experimental dataset is introduced,and the preliminary performances of the ocean model in simulating the global ocean temperature,salinity,sea surface temperature,sea surface salinity,sea surface height,sea ice,and Atlantic Meridional Overturning Circulation(AMOC)are evaluated.The results show that the model is at quasi-equilibrium during the integration of 372 years,and performances of the model are reasonable compared with observations.This dataset is ready to be downloaded and used by the community in related research,e.g.,multi-ocean-sea-ice model performance evaluation and interannual variation in oceans driven by prescribed atmospheric forcing.

CAS-ESM2.0 Model Datasets for the CMIP6 Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP)

The second version of the Chinese Academy of Sciences Earth System Model(CAS-ESM2.0)is participating in the Flux-Anomaly-Forced Model Intercomparison Project(FAFMIP)experiments in phase 6 of the Coupled Model Intercomparison Project(CMIP6).The purpose of FAFMIP is to understand and reduce the uncertainty of ocean climate changes in response to increased CO2 forcing in atmosphere-ocean general circulation models(AOGCMs),including the simulations of ocean heat content(OHC)change,ocean circulation change,and sea level rise due to thermal expansion.FAFMIP experiments(including faf-heat,faf-stress,faf-water,faf-all,faf-passiveheat,faf-heat-NA50pct and faf-heat-NA0pct)have been conducted.All of the experiments were integrated over a 70-year period and the corresponding data have been uploaded to the Earth System Grid Federation data server for CMIP6 users to download.This paper describes the experimental design and model datasets and evaluates the preliminary results of CAS-ESM2.0 simulations of ocean climate changes in the FAFMIP experiments.The simulations of the changes in global ocean temperature,Atlantic Meridional Overturning Circulation(AMOC),OHC,and dynamic sea level(DSL),are all reasonably reproduced.

Inhomogeneous trends in the onset date of extreme hot days in China over the last five decades

基于1960-2018年均一化日最高气温(T_(max))资料,发现中国大部分区域高温初始发生日期(FirstEHD)呈提前趋势,但华北地区一些站点呈推迟趋势,这主要由上述区域T_(max)的长期变化趋势决定,但T_(max)变率的影响也不可忽视.FirstEHD的变化趋势在1990s出现年代际转折,其中新疆,华北和长江流域在1990s前后FirstEHD发生变化,华南地区则表现为1990s前后FirstEHD趋势幅度的不同,但符号保持不变;研究表明FirstEHD趋势的年代际转折转折与大气环流年代际趋势的变化紧密相关.

System bias correction of short-term hub-height wind forecasts using the Kalman filter

Wind energy is a fluctuating source for power systems, which poses challenges to grid planning for the wind power industry. To improve the short-term wind forecasts at turbine height, the bias correction approach Kalman filter (KF) is applied to 72-h wind speed forecasts from the WRF model in Zhangbei wind farm for a period over two years. The KF approach shows a remarkable ability in improving the raw forecasts by decreasing the root-mean-square error by 16% from 3.58 to 3.01 m s−1, the mean absolute error by 14% from 2.71 to 2.34 m s−1, the bias from 0.22 to − 0.19 m s−1, and improving the correlation from 0.58 to 0.66. The KF significantly reduces random errors of the model, showing the capability to deal with the forecast errors associated with physical processes which cannot be accurately handled by the numerical model. In addition, the improvement of the bias correction is larger for wind speeds sensitive to wind power generation. So the KF approach is suitable for short-term wind power prediction.

Interannual variations of dust activity in western Iran and their possible mechanisms

Through an analysis of station observations and reanalysis data,in this study,we investigate the variations of dust activity during 1979-2015 in western and southwestern Iran and their associated mechanisms.The dust day frequency(DDF)is used to identify dust activities.The results show larger interannual variabilities in the DDF in spring and summer,with standard deviations(σ)of 10%and 13%,respectively.Correlation analyses reveal that the interannual variability of DDF in western Iran is largely regulated by wind speed,precipitation and soil moisture in the region.The regional mean spring(March-May)DDF shows strong negative correlations with spring precipitation(correlation coefficient R=−0.5)and soil moisture(R=−0.6)over western to southwestern Iran,but strong positive correlations between the springtime DDF and surface winds can be found with the R reaching 0.4-0.6.Dust activity in the summer dry season(June-August)is mainly associated with surface winds over southwestern Iran,especially in regions near the Persian Gulf,where the R between the DDF and surface winds reaches 0.5.Meanwhile,the summer DDF also shows strong negative correlations(R<−0.4)with soil moisture of the top layer in the middle to southern part of the region.These results highlight the key roles of wind speed,precipitation and soil moisture in determining the interannual variation of dust activities in western and southwestern Iran.