Comprehensive marine atmospheric turbulence observation data, meteorological sounding and sea surface conditions in the South China Sea were employed to analyze and parameterize the vapor profile in the stable marine atmospheric boundary layer. The observations involved a three-dimensional ultrasonic anemometer, water vapor carbon dioxide analyzer, radiosonde and buoy. This paper theoretically determined that the water vapor profile function φq differs from the temperature profile function φh and that φq should be independently parameterized. A linear relationship existed between the dimensionless water vapor gradient and stability parameters based on the observation results, and φq was then obtained as φq(z/L)=a(z/L)+b, in which the stability covered the stability range (z/L>1). This result was applied in the Tropical Ocean-Global Atmosphere Coupled-Ocean Atmosphere Response Experiment (COARE) bulk flux algorithm, and the simulation of the latent heat flux was improved.

A reasonable representation of orographic anisotropy in earth system models is vital for improving weather and climate modeling. In this study, we implemented the orographic drag scheme, including 3-D orographic anisotropy (3D-AFD), into the Chinese Academy of Sciences Earth System Model version 2 (CAS-ESM 2.0). Three groups of simulations named sensitivity run, medium-range forecast, and seasonal forecast respectively were conducted using the updated CAS-ESM model together with the original 2-D isotropic scheme (2-D) and the 3-D orographic anisotropy for the eight-direction scheme (3D-8x) to validate its performance. Sensitivity runs indicated that the simulated drag using the original 2-D scheme did not change with the wind directions, while the simulated drag using the updated 3D-AFD showed a smoother transition than that using 3D-8x. The 3D-AFD and 3D-8x had also about 80% larger drag and smaller wind speed of 1m/s than that of the 2-D scheme. Enhanced drag in the medium range and seasonal forecast using the updated CAS-ESM both alleviated the bias of the overestimated wind speed and the cold bias over mountain regions in the 2-D scheme. This was more apparent in winter (0.4-0.5 m/s and ~1K) than that in summer (0.1 m/s and ~0.1K) for the northern hemisphere region, such as the Tibetan Plateau. The vertical wind profile was also improved in the seasonal forecast. The results suggested that a reasonable representation of the orographic anisotropy was important in climate modeling, and the updated model of CAS-ESM with 3D-AFD alleviated the bias of the mountain wind.

We analyzed the variations in the mean wind field, turbulence, and turbulent flux at the landfall sites of three typhoons using observational data obtained from an offshore monitoring platform. These variations were different for onshore and offshore winds. The turbulent fluctuation intensity and friction velocity increased with wind speed both before and after landfall. However, the turbulent flow decreased with increasing wind speed during landfall. The relationships between the friction velocity and drag coefficient and the wind speed were affected by whether the typhoon makes landfall, and the relative position of the landfall site of the typhoon and the observation site.