Comparisons of Air-Sea Flux Parameterizations on the Intensity Prediction of GRAPES-GFS

GRAPES-GFS is the Global version of GRAPES-the Unified Global/Regional Assimilation PrEdiction System developed by China Meteorological Administration. GRAPES-GFS was put into operational running in 2016 providing 240h forecasts. The horizontal resolution is 0.25°with 60 vertical levels.
In order to study the Impacts of different Air-Sea Flux parameterizations to the TC intensity prediction of GRAPES-GFS， three different momentum roughness length schemes and four moisture roughness length schemes are compared using GRAPES-GFS model with NCEP FNL as the initial conditions. Two groups of experiments are carried out: (1) Same formula for moisture roughness length scheme with three different formulas for momentum roughness length scheme; (2) Same momentum roughness length formula with four different moisture roughness length formulas.
The results of two TCs in North West Pacific Ocean in 2016 (No.1621 and No.1622) show that the scheme of moisture roughness length dominates the intensity of TCs: experiments (1) intends to produce the same minimum sea level pressure with slight different maximum 10m winds; Experiments (2) produce TCs with big different intensity; The results from experiments (1) also indicate that the QFX and model lower level water vapor could be very different around the TC development region: the larger the momentum roughness length, the larger the QFX and the water vapor especially within the boundary layer.