Detection of the atmospheric pressure depression in the center of Tokyo using data corrected by assuming hydrostatic equilibrium : A case study when a typical urban heat island existed in the center of Tokyo at nighttime summer

The present study represents the first ever investigation of the atmospheric pressure distribution in the Tokyo ward area at nighttime in summer using observational data. Data were sourced from Tokyo\u27s high density Metropolitan Environmental Temperature and Rainfall Observation System (METROS). The METROS data required correction in order to determine the detailed pressure distribution in the city, due to the instrument errors specific to each station. Since the METROS observational instruments had already been removed, we corrected the atmospheric pressure data using measured pressure differences between the Tokyo Meteorological Observatory and each METROS station, at a time when the temperature at each METROS station was equal to that at the Tokyo Meteorological Observatory, based on temperature measurements under hydrostatic equilibrium conditions. The corrected pressure distribution calculated in this study was found to be reasonable because it was spatially consistent with the air temperature distribution, wind system, and convergence zone. In a case study when a typical urban heat island existed in the center of Tokyo, we detected a significant atmospheric pressure decrease of 0.2 or 0.3 hPa in the center of Tokyo compared to surrounding areas