Effects of the Hawaiian Islands on the vertical structure of low‐level clouds from CALIPSO lidar

Abstract

AbstractThe steady northeast trade winds impinge on the Hawaiian Islands, producing prominent island wakes of multispatial scales from tens to thousands of kilometers. Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) reveal rich three‐dimensional structures of low‐level clouds that are induced by the islands, distinct from the background environment. The cloud frequency peaks between 1.5 and 2.0 km in cloud top elevation over the windward slopes of the islands of Kauai and Oahu due to orographic lifting and daytime island heating. In the nighttime near‐island wake of Kauai, CALIPSO captures a striking cloud hole below 1.6 km as the cold advection from the island suppresses low‐level clouds. The cyclonic eddy of the mechanical wake behind the island of Hawaii favors the formation of low‐level clouds (below 2.5 km), and the anticyclonic eddy suppresses the low‐level cloud formation, indicative of the dynamical effect on the vertical structure of low‐level clouds. In the long Hawaiian wake due to air‐sea interaction, low‐level clouds form over both the warmer and colder waters, but the cloud tops are 400–600 m higher over the warm than the cold waters. In addition, the day‐night differences and the sensitivity of low‐level clouds to the background trade wind inversion height are also studied.