Contributions of temperature and humidity to intra-city variations in humid heat

Abstract

In this study, we investigated the intracity variation of humid heat in consideration of the contributions from temperature and humidity. Data were collected from mobile surveys in a mid-latitude industrial city. We found greater humid heat in built-up neighborhoods than in rural neighborhoods. Land surface temperature exaggerates the disparity in heat exposure as opposed to air temperature, although their spatial variations bear a strong resemblance. Humid heat is more variable across the city at night than during the day. Its nighttime variation is stronger in the cold season than in the warm season. Weather exerts a strong influence on the spatial variation in humid heat. The greatest variation was observed in the conditions of weak wind, low solar radiation, and high soil moisture in the day, and in the weak-wind and dry-soil conditions at night. The daytime humid heat increases in the built-up neighborhoods because these neighborhoods dissipate surface moist static energy less efficiently than the rural neighborhoods. The nighttime humid heat varies within the city mainly because the release of heat stored in the built-up neighborhoods is at a higher rate than the heat release from the rural soil.