Implementation of tidal parameterization in the Weather Research and Forecasting (WRF) model

Abstract

In this study, the Noah land surface model with a tidal parameterization was implemented in the WRF model. Newly added inputs included gridded tidal data that indicated the presence of a tidal flat, and a time varying water layer thickness over the tidal flat. Two simulations were performed in an online mode, namely, a simulation without tidal effects (CNTL) and simulation with tidal effects (TIDE). A comparison between the simulations and observations at flux tower showed that the surface heat and momentum fluxes were well reproduced in the TIDE simulation both in the magnitude and variation. In spite of better surface flux simulations, the air temperatures were slightly better simulated in the TIDE simulation than in the CNTL simulation during nighttime only. The 10 m wind speed was slightly overestimated in the TIDE compared to the CNTL simulation. The mean differences in the field variables between the TIDE and CNTL simulations were examined for four cases during the simulation period (inundation and exposed conditions at night and inundation and exposed conditions during the day). Tidal grids were classified into two groups depending on the land use type in the CNTL simulation as either the land to tide (LT) group or the water to tide (WT) group. The magnitude of the 2 m air temperature difference between the two simulations was generally larger on LT group than on WT group. During the day, both the 2 m air temperature and the planetary boundary layer height (PBLH) decreased under inundation conditions over LT group. The impact of the tidal flat on 10 m wind and PBLH extended inland beyond the tidal flats during the daytime inundation period.