Observational studies of the air flow over Nantucket Island during the summer of 1950

Abstract

The observations presented here were undertaken as a continuation of a broader program to investigate atmospheric convection. One phase of this study concerns the relation between convective motions, their energy sources, and the structure of the atmosphere prior to their onset. The structure of the atmosphere is described in terms of such parameters as temperature, humidity, velocity, turbulence, and distribution of these in space. An oceanic island was chosen as the site for this phase of the study primarily because it serves as a localized and clearly defined energy source for convective motions. Nantucket was selected from the many accessible islands in the Woods Hole area, nearly all known to produce convective cloud streets, mainly because of its flat, smooth topography. Because its elevation never exceeds 15 meters above sea level and because it contains no large trees, hills or other obstructions, the effect of heating the air from below is rather well isolated due to minimization of the barrier and frictional effects. Previous observational work (Malkus, Bunker, and McCasland, 1949) indicates that such heating is the main energy source for the observed convective motions and constitutes a necessary but not suffcient condition for their production. This conclusion is corroborated and extended by the present data.