Abstract. The turbulent flux parameterization schemes in surface layer are crucial for air pollution modeling. The pollutants prediction by atmosphere chemical model exist obvious deficiencies, which may be closely related to the uncertainties of the momentum and sensible heat fluxes calculation in the surface layer. In this study, a new surface layer scheme (Li) and a classic scheme (MM5) were compared and evaluated based on the observed momentum and sensible heat fluxes in east China during a severe haze episode in winter. The results showed that it is necessary to distinguish the thermal roughness length z0h from the aerodynamic roughness length z0m, and ignoring the difference between the two led to large errors of the momentum and sensible heat fluxes in MM5. The error of calculated sensible heat flux was reduced by 54 % after discriminating z0h from z0m in MM5. Besides, the algorithm itself of Li scheme performed generally better than MM5 in winter in east China and the momentum flux bias of the Li scheme was lower about 12%, sensible heat flux bias about 5 % than those of MM5 scheme. Most of all, the Li scheme showed a significant advantage over MM5 for the transition stage from unstable to stable atmosphere corresponding to the PM2.5 accumulation. The momentum flux bias of Li was lower about 38 %, sensible heat flux bias about 43 % than those of MM5 during the PM2.5 increasing stage. This study result indicates the ability of Li scheme for more accurate describing the regional atmosphere stratification, and suggests the potential improving possibilities of severe haze prediction in east China by online coupling it into the atmosphere chemical model.
LAS-Derived Determination of Surface-Layer Sensible Heat Flux over a Heterogeneous Urban Area
