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Spaceborne microwave sensors, such as microwave scatterometers, radar altimeters, and microwave radiometers, can observe the sea surface day and night and are not affected by clouds. Except for the synthetic aperture radar, their spatial resolution is in the order of 10 km. While visible and infrared radiometers provide high-resolution images of chlorophyll a concentration and sea surface temperature, microwave sensors focus on global observations of physical parameters of the sea surface. To achieve accurate observation, it is indispensable to develop algorithms that are based on the physical processes at the air-sea boundary, evaluate observation accuracy, comprehend the error characteristics, and provide feedback for algorithm improvement. In this paper, I would like to summarize my research on ocean observations using three different types of microwave sensors and their applications as well as describe future prospects. [ABSTRACT FROM AUTHOR]

This study introduces temporal and spatial variations of microwave radiation at the slope area of Antarctica based on in situ microwave observations. The observations were conducted by using portable microwave radiometers of 6,18, and 36 GHz in January 2017. The continuous observation at S17 showed a rapid increase of brightness temperature of all frequencies in daytime. Snow melting seems to have caused this increase. The largest increase of brightness temperature was observed with the low frequency band of 6 GHz horizontal polarization. The amount of increase was 70 K. The higher frequencies of 36 and 18 GHz showed an earlier increase, followed by the increase at the low frequency of 6 GHz. This time difference is expected because the lower frequency may be influenced by emission from the deeper snow layer. As determined from observation along the 80 km traverse route between S17 and H128, the brightness temperature increased generally toward the inland; however, the lowest brightness temperature was observed locally around S17. The refrozen ice layers in the coastal snow layers seem to have caused the low emission at S17. Although the satellite microwave observation could reveal the general decrease of brightness temperature from coast to inland, the local low brightness temperature around S17 was not revealed clearly. The satellite observation showed a 5K increase when the in situ observation recorded a large increase of 70 K. These results imply that the satellite observation missed some local and temporal variations. [ABSTRACT FROM AUTHOR]