Assessing diel urban climate dynamics using a land surface temperature harmonization model

Abstract

ABSTRACTThe main objective of this study is to examine how climate gradients (coastal to inland climate) and land-cover types affect land surface temperature (LST) diel variation. To achieve this, we applied LST harmonization model, which integrates LST at daytime and night-time using sine and cosine functions, to reconstruct a complete diel LST curve for census block groups (CBGs) with both highly vegetated and impervious land-cover types in 10 major cities of the Los Angeles region distributed throughout the coastal to inland climate gradient. We calculated diel LST metrics of minimum LST (LSTmin), maximum LST (LSTmax), diel LST range (DLSTR), and time of LSTmin and LSTmax for each CBG as well as LST differences between neighborhoods with extensive (>80%) impervious and vegetated surface. First, we examined how distance from coast explained the calculated LST products. Results showed that DLSTR (by factor of 2.50), LSTmax (by factor of 1.57), and LST differences between CBGs with extensive impervious and vegetated surfaces (by factor of 4) were higher for cities in inland compared to the coastal cities. Time of LSTmax shifted by 2.50 h from the coastal cities to the midland (regions located between coastal and inland areas) and then inland. Second, we examined how distance from coast and land-cover types explained estimated LST of CBGs at 14:00. Results showed that distance from coast and land-cover types together explained 81% of LST at 14:00. Percentage of vegetation was the most significant driver to explain LST. We concluded that using seamless LST data enables us to better evaluate temporally informative metrics of LST for use in human health, resource use, and natural resource management at regional scale.