Most of HaRP (Hawaiian Rainband Project 1990) studies focused on the airflow, circulations and rainfall on the windward side of the island of Hawaii. In this study, we studied the thermal fields in the wakes and the lee-side circulations based on the NCAR Electra flight level data and PAM surface data.

In the lee side wake zone, the temperature is higer than its upstream value and the mixing ratio is lower. The maximum positive temperature deviations (~ 2-3 K) and negative mixing ratio deviations (~ 2-4 g per kg) occur in the northern and southern lee-side coasts as a result of adiabatic descent. In both regions, the trade-wind aloft is able to move over the mountain ridges with tops below the trade-wind inversion. The trade-wind inversion in the wake is ~ 350 m lower. The return flow in the wake off the lee-side coast is more humid than other areas of the wake.

For strong trade-wind days, the surface air airflow along the Kona coast is more humid (~ 1 g per kg)than weak trade-wind days, possible due to stronger return flow offshore. The rainfall there is higher when the trade winds are stronger. Along the northwestern and southwestern lee-side coasts, the temperature is higher (~ 1 K) during strong trade-wind days than weak trade-wind days as stronger trade winds aloft move over the ridges and descend in the lee side. In these regions, the rainfall is much less when trade winds are stronger.