Cloud Cover and Wildfire Variations in Vietnam and Southeast Asia

Abstract:

Monitoring fires from space is constrained by cloud cover, particularly in tropical regions. Cloud cover-fire variations were assessed using the CERES SSF1Deg and MODIS active fire (MCD14ML) products in Vietnam and Southeast Asia. Twelve years (2003-2014) of data have been analyzed spatially and temporally at four spatial scales: a) country level; b). 1x1 degree scale; c). land cover type; d). regions. Country-level results suggested Vietnam having the highest monthly cloud cover (72.37%) followed by Cambodia (69.69%), Laos (67.64%), Thailand (67.58%), and Myanmar (59.90%). Strong negative correlation between cloud cover and MODIS active fires has been observed during the biomass burning months (Jan–Apr). Of the different countries, Vietnam also had the lowest monthly fire detections. Pixel by pixel spatial correlation at 1x1 degree suggested negative fire-cloud relationships over the Red River Delta of Vietnam, the forests of northern Laos, and agriculture-dominated peninsulas of Thailand and Myanmar. Among the different land cover types, the average monthly cloud cover varied between 64% - 66%. Further, results from daily data showed the Red River Delta to have consistently more cloud cover (20–40% more) than the Mekong River Delta in Vietnam, with fewer fire detections in the former than the latter. The study highlights potential fire under-detection due to clouds. Our results highlight spatial and temporal variations in cloud-fire relationships and the difficulty of using optical data for fire detection and characterization in persistently cloudy regions.