A case study of the GRAPES single column model

Based on the GCSS WG4 (Global Energy and Water Cycle Experiment Cloud System Study Working Group 4) Case 3 data，A SCM (Single Column Model) experiment is designed to evaluate physics parameterizations performance of the GRAPES (Global and Regional Assimilation and Prediction Enhanced System) over the mid-latitude land in summer. The influences of two different complexity land surface schemes (CoLM and SLAB) on temperature, moisture, and precipitation simulation are also investigated. In the 29 d simulation, it is shown that the magnitudes of simulated precipitation are similar to those of observation, and there are unobvious departures of simulated potential temperature and water vapor mixing ratio from those of observation, suggesting that the design of the experiment is correct. Then the four precipitation subperiod simulations are respectively performed in order to reduce the influence of the model system error. It is found that the simulated accumulated precipitation with the CoLM scheme is more than that with the SLAB scheme for the four subperiods. In the sub-period 3, the first precipitation event is delayed in both simulations, and their correlation coefficients are very small，which may have relation with the fact that area-averaged initial thermodynamic profile is drier than that of the area where precipitation occurred. The analyses of the timeaveraged errors of the potential temperature and water vapor mixing ratio show that the simulation with the CoLM has cold and moist biases in the lower troposphere in the subperiod 1 and 2, while warm and dry biases in other simulations. These biases of potential temperature in the lower troposphere are related with the fact that the simulated surface temperature with the CoLM is lower than that of observed in the sub-period 1 and 2, while higher in other simulations. Moreover, it is found that the simulation with the CoLM simulated more latent heat fluxes and less sensible heat fluxes than observations, which are opposite to the simulation with the SLAB. In the middle and upper troposphere, cold and moist biases correspond to less precipitation for the two simulations in the sub-period 1 and 4 (the simulation with the CoLM has more precipitation in the sub-period 1 due to its false precipitation). Warm and dry biases correspond to more precipitation for the simulation with the CoLM and cold and dry biases correspond to less precipitation for that with the SLAB in the sub-period 2. Both simulations have cold and dry biases which correspond to more precipitation in the sub-period 3.