Research Team Publishes Results from In-Depth Study of Sahel Climate System
Data for these studies were obtained in 2006 by the ARM Mobile Facility stationed in Niamey, Niger; the European Union’s Geostationary Earth Radiation Budget Experiment; and NASA’s Moderate Resolution Imaging Spectrometer. In combining the measurements, the researchers discovered that the onset of the monsoon circulation in the Sahel region initially attenuates the formation of clouds and precipitation by increasing the stability in the lower atmosphere. Following its initiation, the monsoon layer slowly cools and destabilizes through a combination of mid- and high-level cloudiness and nearby upwelling of cold ocean water. This cooling eventually enables the formation of deep, precipitating convective clouds that stimulate a short-lived, vigorous vegetative growth cycle in which vegetative coverage nearly triples over a period of six weeks.
Despite the seasonally varying influence of clouds, dust, water vapor, vegetation, and the other factors, the net amount of thermal radiation lost to space from the atmosphere over the Sahel is, surprisingly, reasonably constant through the year. This constancy in thermal output was shown by the research team to be linked to the greenhouse gas properties of water vapor in the shallow monsoon layer near the surface. The team also demonstrated that clouds strongly affect the solar radiation budget at the surface and at the top-of-the-atmosphere, but that their role in the climate system of the Sahel region is to vertically redistribute heat rather than modulate the rate of solar absorption. [Contact: Mark Miller, Rutgers University, firstname.lastname@example.org]