基于局地气候分区的南京夏季地表热环境研究

The issue of global warming has become increasingly prevalent in recent years. Concurrently, there exists a considerable prevalence of extreme meteorological occurrences in urban environment, exemplified by the intense heat that characterizes the summer season. The urban heat environment has become a research focus under the background of global warming and rapid urbanization. At present, Local Climate Zone (LCZ) represents the principal method of classification employed in the field of urban thermal environment research. In comparison with the traditional urban–rural dichotomy, this approach entails a further subdivision of the city on the basis of the physical characteristics of the buildings and the natural ground cover features. Based on the LCZ system, this paper investigated the summer thermal environment characteristics of the main urban area of Nanjing from two perspectives: interclass and intraclass, using Landsat image inversion of surface temperature. The classification of LCZs divided the study area into 12 categories, of which 8 were designated for building types and 4 were designated for surface cover types. The proportion of building types within the study area was greater than that of ground cover types. The building types exhibited a high proportion of open high-rise (LCZ 4) and dense mid-rise (LCZ 2), which were predominantly concentrated in the central urban areas. The largest surface cover type was bare soil and sand (LCZ F). Results indicated that the thermal environments among LCZ classes showed large differences. Higher building densities had higher mean LSTs. The mean LSTs tended to rise gradually as building height decreased. The time-series trend of the mean temperature for the various LCZ types was highly consistent with the overall mean temperature trend observed in the study area. Large low-rise (LCZ 8) consistently presented high average surface temperatures during the summer months, reaching a maximum of 53.2 ℃ . Moreover, the average surface temperature for each building type was higher than the average surface temperature for the study area as a whole, and the average surface temperature for each natural ground cover type except bare soil or sand was lower than the average surface temperature for the study area as a whole. The mean surface temperature of compact mid-rise (LCZ 2), compact low-rise (LCZ 3), large low-rise (LCZ 8), and heavy industry (LCZ 10) were higher than the overall mean temperature of the study area. Furthermore, this study presented intraclass analysis of different LCZ types using relative rates of change in LST. An increased sensitivity to temperature fluctuations may have adverse effects on human well-being and economic productivity. Another important finding was that the intra-LCZ thermal environment analyses indicated a heightened sensitivity to temperature fluctuations in the following categories: compact mid-rise (LCZ 2), compact low-rise (LCZ 3), heavy industry (LCZ 10), and bare soil and sand (LCZ F). The findings of this study can serve as a valuable reference point and provide insights for further research in the fields of urban planning, the mitigation of the urban heat island effect, and the enhancement of the urban heat environment.