Radio Acoustic Sounding in Urban Meteorological Observations

Meteorological observations are carried out using a mobile Radio Acoustic Sounding System (RASS), a radiosonde system, and ground-based meteorological measurement systems in order to understand urban meteorological conditions. The newly mobile RASS was operated in the one-shot acoustic pulse (OSAP) mode, allowing the measurement of atmospheric temperature up to about 200 m without causing sound pollution. Based on the temperature profiles obtained using the mobile RASS and radiosondes in the Tokyo metropolitan area during the end of February 2000, a marked decrease in temperature within a short period of time was observed. Rare meteorological phenomena such as this can be analyzed based on temperature profiles and ground-based meteorological data that are observed in Tokyo by government offices at a large number of the sites. As a result, temperatures decreased rapidly due to cold airflow into the measurement sites, and the occurrence of the inversion layer was recognized from RASS temperature profiles within a short time interval.