Modelling study of sea breezes in a complex coastal environment

This study investigates a mesoscale modelling of sea breezes blowing from a narrow strait into the lower Fraser valley (LFV), British Columbia, Canada , during the period of 17-20 July, 1985. Without a nudging scheme in the in ner grid, the CSU-RAMS model produces satisfactory wind and temperature fie lds during the daytime. In comparison with observation, the agreement indic es for surface wind and temperature during daytime reach about 0.6 and 0.95 , respectively, while the agreement indices drop to 0.4 at night. In the ve rtical, profiles of modelled wind and temperature generally agree with teth ersonde data collected on 17 and 19 July. The study demonstrates that in la te afternoon, the model does not capture the advection of an elevated warm layer which originated from land surfaces outside of the inner grid. Mixed layer depth (MLD) is calculated from model output of turbulent kinetic ener gy held. Comparison of MLD results with observation shows that the method g enerates a reliable MLD during the daytime, and that accurate estimates of MLD near the coast require the correct simulation of wind conditions over t he sea. The study has shown that for a complex coast environment like the L FV, a reliable modelling study depends not only on local surface fluxes but also on elevated layers transported from remote land surfaces. This depend ence is especially important when local forcings are weak, for example, dur ing late afternoon and at night. (C) 2000 Elsevier Science Ltd. All rights reserved.