资源环境科技发展态势分析平台

The accurate treatment of surface turbulent fluxes is crucial for understanding the exchange of heat and moisture, which plays an important role in precipitation processes. In the bulk formula for estimating surface turbulent fluxes in atmospheric models, the ocean surface is assumed to be saturated with pure water. This study addresses the impact of salinity on the simulated precipitation of a global numerical weather prediction model, along with related physical reasoning, by incorporating sea surface salinity into the saturated vapor pressure over the ocean. The revised saturated vapor pressure algorithm, in which the salinity is considered, decreases the latent heat flux over the ocean, particularly over low-latitude regions, resulting in a 6.3% reduction in the root-mean-square deviation against the Objectively Analyzed Air-sea Fluxes Project (OAFlux) data. The reduced transport of water vapor to the atmosphere suppresses the generation of low-level clouds. This decrease in cloudiness leads to warming near the surface due to increased downward solar radiation and cooling in the lower troposphere due to a lower condensation rate, which enhances vertical turbulent mixing. The resulting dryness within the planetary boundary layer affects the buoyancy of a lifting parcel and contributes to suppressing the occurrence of convective precipitation. The skill score of the simulated precipitation for medium-range forecasts is improved by 3% due to the reduction in light precipitation over tropical oceans.