Structure of Low-level Clouds from CALIPSO Lidar

26 The steady northeast trade winds impinge on the Hawaiian Islands, producing 27 prominent island wakes of multi-spatial scales from tens to thousands of kilometers. 28 Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) reveal 29 rich three-dimensional structures of low-level clouds that are induced by the islands, 30 distinct from the background environment. The cloud frequency peaks between 1.5-2.0 31 km in cloud-top elevation over the windward slopes of the islands of Kauai and Oahu due 32 to orographic lifting and daytime island heating. In the nighttime near-island wake of 33 Kauai, CALIPSO captures a striking cloud hole below 1.6 km as the cold advection from 34 the island suppresses low-level clouds. The cyclonic eddy of the mechanical wake behind 35 the island of Hawaii favors the formation of low-level clouds (below 2.5 km), and the 36 anticyclonic eddy suppresses the low-level cloud formation, indicative of the dynamical 37 effect on the vertical structure of low-level clouds. In the long Hawaiian wake due to 38 air-sea interaction, low-level clouds form over both the warmer and colder waters, but the 39 cloud tops are 400-600 m higher over the warm than the cold waters. In addition, the 40 day-night differences and the sensitivity of low-level clouds to the background trade wind 41 inversion height are also studied.