Spatial influence of agricultural residue burning and aerosols on land surface temperature

Abstract. The biophysical effects of agricultural residue burning, driven by the excessive release of energy and carbonaceous aerosols, remain poorly quantified at the global scale. Residue-based fires have the potential to modify regional climate by altering land surface temperature (LST), highlighting the need for investigation at regional scale. Here, an observation-driven assessment of spatial variations in LST due to concurrent release of energy and aerosols has been made over northwestern India using multiple satellite and reanalysis-based datasets. Year-specific fire pixel density was used to delineate an intensive fire zone characterized by medium-to-large residue-based fire. Geospatial analysis revealed positive association among FRP (fire radiative power), LST and AOD (aerosol optical depth). Over intensive fire zone, a space-for-time approach revealed significant increase in both ΔLST (0.57 °C; 95 % CI: 0.33–0.81 °C) and ΔAOD (0.13; 95 % CI: 0.08–0.17) due to fire. Random Forest non-linear model was employed to regress potential influence of FRP and AOD on LST having several other variables as confounding factors. FRP consistently emerged as the dominant predictor of LST, followed by planetary boundary layer height and aerosols. An increase in relative feature importance of FRP was noted during days having high fire intensity and positive association with LST. Geographically weighted regression further explained spatial heterogeneity in LST modulation by FRP. Overall, this analysis provides the first empirical evidence that residue-based fire contributes to changes in land surface temperature. It further highlights that the magnitude of this perturbation is governed by interannual variations in fire intensity and influenced strongly by prevailing meteorological conditions.