Radiometric Measurements of the Microwave Emissivity of Reproducible Breaking Waves

In a recent experiment the microwave emissivity of foam on calm water was measured to be 0.75 to 0.95 and dependent on polarization [1]. Microwave radiometric measurements of breaking waves on the open ocean showed that the emission due to wave breaking varies with the time dynamics of the wave, as well as with radiometer polarization and viewing angle [2]. However, the inherent intermittency and sparseness of breaking waves makes it very difficult to perform repeatable measurements on the open ocean. Therefore, the authors conducted a wave basin experiment in which reproducible breaking waves were generated every 1-2 seconds. This paper reports preliminary results of the combined observations of polarimetric brightness temperatures and physical characteristics of these waves and foam. These and future results will provide input parameters to bound numerical electromagnetic models for prediction of foam emissivities [3].