Investigating the Spatiotemporal Characteristics and Energy Balance Physical Mechanisms of the Difference between Land Surface Temperature and Air Temperature in Chengdu Based on the WRF Model

With the acceleration of urbanization, the urban heat island effect has become a critical issue in the context of global climate change. As a representative city in southwestern China, Chengdu has experienced pronounced changes in land surface temperature (LST) and near-surface air temperature (T2) as a result of urbanization. To investigate the spatiotemporal characteristics of the discrepancies between LST and T2 in Chengdu under an urbanization background and to elucidate the underlying physical mechanisms, this study integrates meteorological station observations, the MODIS land surface temperature/emissivity monthly product (MYD11C2), and the ERA5-Land reanalysis dataset with numerical simulations from the Weather Research and Forecasting (WRF) model. The variations in land surface temperature and their associated surface energy balance processes are examined across multiple temporal scales and spatial resolutions.

First, this study compares daytime and nighttime land surface temperatures in Chengdu for the years 2003 and 2023. The results indicate that daytime LST derived from MYD11C2 is generally higher than that from ERA5-Land and exhibits a larger range of variability. Secondly, the performance of the WSM6 and Thompson microphysics schemes in simulating air temperature and precipitation over Chengdu was evaluated. By comparing the root mean square errors (RMSEs) against meteorological station observations, the results show that the WSM6 scheme performs slightly better than the Thompson scheme in air temperature simulations, whereas the Thompson scheme exhibits a clear advantage over WSM6 in precipitation simulations. These findings indicate that the choice of microphysics scheme exerts a significant influence on model performance for different meteorological variables, and that an appropriate scheme should be selected according to the specific research objectives.

To further elucidate the mechanisms underlying the divergence between land surface temperature and air temperature, this study integrates a surface energy balance analysis based on the WRF model to investigate the primary drivers of the LST–T2 differences. The results demonstrate that variations in surface energy partitioning—particularly changes in net radiation, sensible heat flux, and latent heat flux—are key factors governing the formation of discrepancies between LST and T2. In addition, urban surface characteristics, such as the proportion of impervious surfaces and building density, play an important role in modulating the differences between land surface temperature and near-surface air temperature.