El Nino Watch
How much sunlight is blocked by particles (smoke, dust, pollution) in the whole air column. Below 0.1 = clear; about 1 = very hazy; above 2-3 = very high concentrations.
Map layers
Aerosol optical depth (AOD) is a number without units that measures how much the particles in the air dim the sunlight. NASA's guide: less than 0.1 is a crystal clear sky; a value of 1 means very hazy; above 2 or 3 means very high concentrations.
AOD is for the whole column of air, from the ground to the top of the atmosphere. A thick smoke layer high up can give a high AOD while the air you breathe is fine, and the reverse. For what you breathe, use PM2.5 (see PM2.5 and the Thai bands).
Yellow/orange/red-brown patches (see legend) = more particles. Look for plumes spreading from fire areas in Sumatra and Borneo towards the Malay Peninsula.