Comparisons of Aircraft and Tower Measurements around Tarama Island during the AMTEX ‘75

Abstract

During the field observation period of the Air Mass Transformation Experiment in 1975 (AMTEX ?75), one of the boundary-layer research flights of the National Center for Atmospheric Research (NCAR) Electra aircraft was conducted in the vicinity of Tarama Island. A 50-m onshore observation tower was located on the southwestern coast of Tarama Island, and a 12-m offshore observation tower on the northern reef. We compare and discuss mean profiles of dry- and wet-bulb temperature, wind speed and direction, and turbulent fluxes of latent and sensible heat and momentum observed by these three observing platforms. We found that the 50.m onshore tower, which was about 3.5 km downwind of the shoreline, and the airplane flight legs over the island at 140 and 160 m height were in the island-modified air. This resulted in large differences between ocean and island measured fluxes, smaller differences in the variances and almost no differences in the means. Thus, we found that for the conditions of this experiment it is feasible to use the island-measured values of mean quantities as characteristic of the ocean. but the fluxes and variances are characteristic of the island.