Cloud-Free Land Surface Temperature Reconstructions Based on MODIS Measurements and Numerical Simulations for Characterizing Surface Urban Heat Islands

Abstract

Land surface temperature (LST) data in the thermal infrared (TIR) band measured by the moderate-resolution imaging spectroradiometer (MODIS) instrument are critical for studying surface urban heat islands (SUHIs); however, these acquired TIR LST data are contaminated by clouds, so it is crucial to develop a method to generate cloud-free LST products. In this article, employing Tianjin as the research area, we combined the weather research and forecasting model with a random forest and a spatial optimization algorithm to propose a cloud-free MODIS-like model (WRFFM). The model can reconstruct cloud-free MODIS-like LSTs and SUHIs are studied. The spatial patterns of the WRFFM LSTs and the MODIS LSTs are consistent; the correlation coefficients in July and December range from 0.8 to 0.91 and 0.8 to 0.93, respectively, and the root mean square errors range from 0.5 to 3.8 K and 0.4 to 1.8 K, respectively, indicating that the modeled results are accurate. We use these WRFFM LSTs to study SUHIs and evaluate the deviations between the MODIS SUHIs and WRFFM SUHIs. When the proportion of clear-sky pixels is below 30%, the deviation is above 3 K, and when the proportion of clear-sky pixels is above 80%, the deviation is below 0.6 K. The results indicate that the developed model can be applied to improve the study of SUHIs and that the number of clear-sky pixels for a city is an important factor that affects the bias relative to the actual SUHI .

Keywords

• Cloud contamination
• land surface temperature (LST)
• moderate-resolution imaging spectroradiometer (MODIS)
• surface urban heat island (SUHI)
• weather research and forecasting (WRF)