On the structure of trade-wind air below cloud

Abstract

The moisture and temperature structure of the trade-wind mixed layer are compared under conditions of strong versus weak trade. The data used are two series of aircraft psychrograph soundings made over the ocean near Puerto Rico in early spring. The first in conditions of strong undisturbed trade and high zonal index (April 10 - 28, 1946) and the second under conditions of weak rather disturbed trade and low zonal index (March 18 - April 7, 1953). The weak trade soundings show a less homogeneous moisture distribution and a less stable temperature lapse rate. Considerable variation in structure of the lowest air accompanies changes in the trade regime which may give rise to significant fluctuations in energy input at the source region for atmospheric circulations. The importance of wind stirring in the upward transfer of moisture is indicated, which may affect the formation of trade cumulus clouds. Further studies investigating the relation between air and ocean structure at their boundary are suggested by the evidence herein, which may relate to the formation of tropical storms.