Fire Regime Impacts on Postfire Diurnal Land Surface Temperature Change Over North American Boreal Forest

Abstract Wildfire is the most prevalent natural disturbance in the North American boreal forest (NABF) and can cause postfire land surface temperature change (Δ T fire ) through biophysical processes. Fire regimes, such as fire severity, fire intensity, and percentage of burned area (PBA), may influence Δ T fire through their impacts on postfire vegetation damage and, if so, there may be important feedbacks between fire regime and climate warming through biophysical effects. Here, we employ satellite observations to investigate postfire diurnal Δ T fire across NABF. We further use a stepwise multiple linear regression model to examine the driving factors for Δ T fire by incorporating latitude, fire regime variables, and their interactions. Our results demonstrate a pronounced asymmetry in diurnal Δ T fire , characterized by daytime warming in contrast to nighttime cooling. Clear latitudinal patterns are found in Δ T fire , with stronger effects in lower latitudes. Such latitudinal patterns of Δ T fire , especially the daytime one, are driven by both latitudinal patterns in fire regimes and an increased sensitivity of Δ T fire to fire regime as the latitude decreases. The multiple linear regression model explains 37% of the variance in daytime Δ T fire , whereas for the nighttime Δ T fire the explanatory power is rather low (5%). For daytime Δ T fire , fire severity accounted for most (43.65%) of the model explanatory power, followed by PBA (24.60%) and fire intensity (13.10%). Our results highlight important fire regime impacts on daytime Δ T fire and, further, on the annual Δ T fire , suggesting that fire might amplify future boreal climate change through positive feedbacks between fire regime and postfire surface warming.