This can happen because water vapor in the atmosphere condenses on certain types and sizes of aerosols called cloud condensation nuclei to form clouds; when enough water vapor accumulates, rain droplets are formed.
A study published in the journal Environmental Research Letters, led by Charles Ichoku, a senior scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, seeks to shed light on the connection.
"There is a tendency for the net influence of fire to suppress precipitation in northern sub-Saharan Africa," he said.
Even within dry seasons, the amount of water decreased in areas with more humid climates as the burning became more severe.
The results so far show only a correlation between fires and water cycle indicators, but the data gathered from the study is allowing scientists to improve climate models to be able to establish a more direct relationship between biomass burning and its impacts on drought.
Future modeling may explain some of the study’s seemingly paradoxical findings, including the fact that, even as fires decreased by 2 to 7 percent each year from 2006 to 2013, precipitation during those years did not increase proportionately.
Ichoku thinks one possible reason a decrease in fires didn’t result in more precipitation has to do with the change in the types of lands that are being burned.
He notes that recent droughts have drawn people to farm areas that have more water.
"The removal of vegetal cover through burning would likely increase water runoff when it rains, potentially reducing their water retention capacity and invariably the soil moisture," Ichoku said.
Biomass burning, land-cover change, and the hydrological cycle in Northern sub-Saharan Africa.