Numerical Simulations of Airflow and Cloud Distributions over the Windward Side of the Island of Hawaii. Part II: Nocturnal Flow Regime*

Abstract

Abstract Numerical experiments are performed with the fifth generation Mesoscale Model to study the evolution of island airflow, thermodynamic fields, and clouds over the island of Hawaii at night. The model has successfully simulated the major observed features associated with the nocturnal flow regime. These include the formation of nocturnal inversion, development, gradual offshore extension and deepening of the katabatic flow, shifting of the overall cloudy areas from the windward slopes to the ocean, and generation of clouds within the simulated offshore convergence zone. Furthermore, it is also shown that rain evaporative cooling affects the depth, strength, and offshore extension of the katabatic flow. In the early evening, the nocturnal cooling provides the land–sea thermal contrasts for the development of the simulated downslope flow on the windward slopes. With continued nocturnal cooling and rain evaporation, the simulated katabatic flow extends toward the coast. The simulated convergence zone ...