Smoke from forest fires can prevent clouds from forming raindrops. Soot
particles in the smoke cause many small water droplets to condense, preventing
the buildup of large droplets. Small droplets remain suspended in the
atmosphere instead of falling as rain.
The image above, taken over the Indonesian island of Borneo,
illustrates this phenomenon from two instruments aboard
the Tropical Rainfall Measuring Mission (TRMM). The Visible and Infrared
Sensor (VIRS) detects fires and shows the extent of clouds and smoke, while
the Precipitation Radar (PR) detects cloud water droplet size and rainfall.
Smoke from the fires (red dots) in the upper right combined with clouds in
the center of the image. TRMM's precipitation radar showed the small
size (darker teal) of the water droplets suspended in these clouds compared
to the larger (brighter teal) droplets in the clean clouds to the left.
Only the clean
clouds produced significant rainfall (blue).
Learn more about the effects of particles on clouds in
Every Cloud had a Filthy Lining.
And the Tropical Rainfall Measuring Mission in the TRMM Fact Sheet