Solid particles and liquid droplets in the air come in a range of sizes, but those smaller than 2.5 micrometers pose the greatest risk to human health.
In the weeks before India’s monsoon rains, dust, smoke, and haze build over the Ganges River Plain. This image provides a profile of the atmosphere during one of those pollution periods.
Simulations of air pollution from the GOCART model help show how much skies have cleared over Europe and North America even as they have darkened over Asia in the last decade.
By measuring precisely how much light is reflected at visible and near-infrared wavelengths, the MODIS sensors can also distinguish between aerosol plumes of large particles (more than 1 micrometer) and small particles (less than 1 micrometer).