General air temperature and humidity features of local climate zones: A multi-city observational study in eastern China

Abstract

The local climate zone (LCZ) scheme has been widely applied in urban climate studies. However, most field observations were conducted in individual cities and focused solely on air temperature. Few investigations have focused on the general climatic features of LCZs. This study aimed to obtain a reliable understanding of the air temperature and humidity features of LCZs by conducting multi-city observations. Towards this goal, fixed stations were established using temperature/humidity loggers deployed at 17 pairs of urban and rural sites in 15 cities of eastern China for one year. All the rural reference sites were LCZ D (low plants). Differences in air temperature (ΔT) and humidity ratio (ΔW) between the urban and rural sites (LCZ X − LCZ D) were analyzed on multiple time scales (diurnal, seasonal, and annual). In addition, we assessed urban-rural differences in the frequency and duration of heat and cold waves and the effects of local urban climates on building energy demands and human thermal stress. The results showed that: (1) the nocturnal ΔT values for ‘ideal’ days (calm and clear days) exhibited distinguishable differences among different LCZ types, but approximately similar magnitudes for urban sites belonging to the same LCZ type; (2) the analysis of ΔW revealed that moisture deficits and excesses were common occurrences in urban sites across cities; and there was no discernible pattern in ΔW among LCZs; (3) compared to their rural counterparts, all urban sites exhibited remarkable increases in heat-wave incidence, cooling energy demand, and heat exposure risk. These findings will help better understand the general climatic features of LCZs and develop adaption strategies.