Evapotranspiration-dominated biogeophysical warming effect of urbanization in the Beijing-Tianjin-Hebei region, China
Given the considerable influences of urbanization on near-surface air temperature (T a ) and surface skin temperature (T s ) at local and regional scales, we investigated the biogeophysical effects of urbanization on T a and T s in the Beijing-Tianjin-Hebei (BTH) region of China, a typical rapidly urbanizing area, using the weather research and forecasting model (WRF). Two experiments were conducted using satellite-derived realistic areal fraction land cover data in 2010 and 1990 as well as localized parameters (e.g. albedo and leaf area index). Without considering anthropogenic heat, experimental differences indicated a regional biogeophysical warming of 0.15 °C (0.16 °C) in summer T a (T s ), but a negligible warming in winter T a (T s ). Sensitivity analyses also showed a stronger magnitude of local warming in summer than in winter. Along with an increase of 10% in the urban fraction, local T a (T s ) increases of 0.185 °C (0.335 °C), 0.212 °C (0.464 °C), and 0.140 °C (0.220 °C) were found at annual, summer, and winter scales, respectively, according to a space-for-time substitution method. The sensitivity analyses will be beneficial to get a rough biogeophysical warming estimation of future urbanization projections. Furthermore, a decomposed temperature metric (DTM) method was applied for the attribution analyses of the change in T s induced by urbanization. Our results showed that the decrease in evapotranspiration-induced latent heat played a dominate role in biogeophysical warming due to urbanization in BTH, indicating that increasing green space could alleviate warming effects, especially in summer.
KeywordsUrbanization Local effect Surface energy balance Numerical modeling
This research is supported by the Strategic Priority Research Program (XDA19040301) and Key Research Program of Frontier Sciences (QYZDB-SSW-DQC005), the Chinese Academy of Sciences (CAS), the National Natural Science Foundation of China (41501484, 41671425, and 41701501), and the “Thousand Youth Talents Plan”. We want to thank ECMWF for providing ERA-Interim reanalysis data (http://apps.ecmwf.int/datasets/), Global Land Cover Facility (GLCF) and Beijing Normal University for providing Global LAnd Surface Satellite (GLASS) albedo/LAI data (http://glcf.umd.edu/data/), and China Meteorological Data Service Center (CMDC) for providing grid air temperature observations (http://data.cma.cn/data/detail/dataCode/SURF_CLI_CHN_TEM_MON_GRID_0.5/). We also want to thank Xiaoming Hu from the University of Oklahoma and Jilin Yang from the Institute of Geographic Sciences and Natural Resources Research, CAS for their helps to improve the manuscript, as well as the three anonymous reviewers for their insightful comments.
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