MICROWAVE RADIOMETRY AND ITS APPLICATION TO MARINE METEOROLOGY AND OCEANOGRAPHY

Past developments in microwave radiometry are reviewed to establish a continuity between microwave physics, engineering, and applications to marine meteorology and oceanography. Molecular oxygen, water vapor, and liquid water absorb, emit, and scatter microwave radiation. The ocean reflects or scatters a majority of the microwave radiation incident upon its surface and emits microwave energy. The functional relationship between these interactions and the physical state of the atmosphere and hydrosphere are described in detail. The emission of sea water is almost constant with temperature and salinity for frequencies of 8 GHz to 30 GHz, is linearly proportional to temperature for frequencies near 5.4 GHz, and is strongly dependent upon salinity for frequencies near 1 GHz. Sea foam causes the microwave emission of the sea to increase greatly for all microwave frequencies and angles of viewing. The natural variability of water vapor in the atmosphere affects the absolute value of upwelling microwave radiation greatly for frequencies near 22.235 GHz. The attenuation and emission of the atmosphere are predictable for frequencies less than 8 GHz. Microwave measurements near 5.4 GHz and 1 GHz may be used to survey, remotely, the temperature and salinity of coastal water. Microwave measurements near 22.235 GHz may be used to measure the precipitable water in the atmosphere.