Smoke from a number of agricultural fires is currently blanketing Thailand and Cambodia. This is shown below in the satellite image from the MODIS instrument on the TERRA satellite. The red dots are classed as ‘thermal anomalies’ by the satellite instrument and are usually indicative of fires burning in these locations.
The majority of the fires are occurring in grass and cropland areas, which are the bale brown portions of the land surface in the image. This is indicative of agricultural burning, where farmers clear land and use the fires to recycle nutrients ahead of the growing season. In South-East Asia, the fire season usually runs from January to April/May.
While the burning is beneficial to farmers, it isn’t too good for air quality in the region. The smoke generated by the fires has built up over Cambodia and Thailand (contrast the clearness of the image in the top-left over Myanmar with the haze to the east). The MODIS instrument on the satellite can also measure the amount of pollution in the atmosphere. This is known as the aerosol optical depth, which is well above 0.5 across the region. For context, a fairly polluted day in North-Western Europe might seen an aerosol optical depth of around 0.2.
This build up of pollution is harmful to health and can also cool or warm the atmosphere depending on the properties of the smoke. The side affects of such changes are uncertain but they could for instance alter atmospheric circulation patterns and rainfall.
Fires are a frequent occurrence across the globe and their impact can have long lasting consequences on our health and climate.