Two Major Experiments in the Humidity Exchange over the Sea (HEXOS) Program

Abstract

Humidity Exchange over the Sea (HEXOS) is an international program for the study of evaporation and spray droplet flux from sea to air. The program includes measurements in the field, simulation studies in wind tunnels, interpretive studies such as flow distortion modeling, boundary-layer modeling and development of parameterization for use in synoptic, and climatic models of the atmosphere and ocean. The HEXOS Main Experiment (HEXMAX) was carried out in October and November of 1986 at the Dutch offshore research plat-form Meetpost Noordwijk (MPN) and from ship, aircraft, and shore stations in the vicinity. Evaporation, wind stress, and heat flux were determined at all stations using combinations of eddy correlation, dissipation, and profile methods. Concurrent measurements of spray and aerosol distributions and other relevant parameters, and the regular occurence of favorable winds and weather make the HEX-MAX dataset unique in its completeness and in the range of conditions covered. Some preliminary results are reported. The series of the French Couche Limite Unidimensionelle Stationnaire d'Embruns (CLUSE) experiments is designed to study in a simulation tunnel the surface flux of droplets generated by bursting bubbles and the interaction of these droplets with the turbulent fields of humidity, temperature, and velocity in the boundary layer. Grand CLUSE, in the spring of 1988, simulated aerosol generation and interactions of the aerosols with turbulent fields of temperature, humidity and wind. A series of four smaller Petit CLUSE experiments addressed specific techniques and the simulation of specific processes.