Diurnal Variation of Surface Airflow and Rainfall Frequencies on the Island of Hawaii

Abstract

Abstract The high-resolution Portable Automated Mesonet data from the Hawaiian Rainband Project are used to document the circulation over the entire island of Hawaii for the first time. It is shown that the surface airflow and rainfall occurrences over the island are strongly modulated by the diurnal heating cycle. Most areas over the island show daytime upslope and nighttime downslope components separated by morning and evening transitions. On the windward slope, the onset of the downslope (upslope) wind during the evening (morning) transition starts on the slopes and progresses downward. The effects of island blocking are also evident. On the windward slopes of Mauna Kea and Mauna Loa, the mean winds are weak (∼1 m s−1) due to flow deceleration. Flow splitting occurs in the Hilo Bay area as the trade winds are forced to move around the island. On the lee side, the trade winds are absent. For stronger trade-wind days, the island blocking is more significant with a higher surface pressure (0.2-0.5 hPa) on...