Scientists find that carbonaceous aerosols could suppress regional rainfall over tropical Africa through the aerosol-cloud interaction mechanism.
Subtropical North Africa has been subject to extensive droughts in the late 20th century, linked to changes in the sea surface temperature. Aerosol indirect effects also appear to play an important role in suppressing regional rainfall over tropical Africa.
Between 1950 and 1980, the Sahel region, a large swath of the African continent located between the tropical rainforests and the Saharan desert, has experienced a large reduction in rainfall. Various factors affecting climate have been suggested as the driver of this drastic change in Sahel rainfall. This research points to carbonaceous aerosols, carbon-containing particles emitted from biomass burning, as one mechanism that suppresses regional rainfall through their interactions with clouds.
Subtropical North Africa has been subject to extensive droughts in the late 20th century, a phenomena often linked to changes in the sea surface temperature. However, climate model simulations that are forced by observed sea surface temperatures (SSTs) cannot reproduce the magnitude of the observed rainfall reduction. Scientists at the Department of Energy’s Pacific Northwest National Laboratory and collaborators show that aerosol indirect effects on clouds provide an important positive feedback mechanism that increases agreement with rainfall changes. Model results from two sets of sensitivity experiments were designed to distinguish the role of aerosol direct/semi-direct and indirect effects on regional precipitation. The results indicate that changes in cloud properties due to the presence of carbonaceous aerosols are a key mechanism to explain the reduced rainfall over subtropical North Africa.
Contacts (BER PM)
Earth System Modeling Program
Philip J. Rasch
Pacific Northwest National Laboratory
Support was provided by the US Department of Energy, Office of Science, Office of Biological and Environmental Research Program through the Earth System Modeling program.
J-H Yoon, P.J. Rasch, H. Wang, V. Vinoj, and D. Ganguly, “The Role of Carbonaceous Aerosols on Short-Term Variations of Precipitation over North Africa.” Atmospheric Science Letters 17(7): 407-414. (2016) [DOI: 10.1002/asl.672] (Reference link)
SC-23.1 Climate and Environmental Sciences Division, BER
BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER
Aug 24, 2019
New Approach for Studying How Microbes Influence Their Environment
A diverse group of scientists suggests a common framework and targeting of known microbial processes [more...]
Aug 08, 2019
Nutrient-Hungry Peatland Microbes Reduce Carbon Loss Under Warmer Conditions
Enzyme production in peatlands reduces carbon lost to respiration under future high temperatures. [more...]
Aug 05, 2019
Amazon Forest Response to CO2 Fertilization Dependent on Plant Phosphorus Acquisition
AmazonFACE Model Intercomparison. The Science Plant growth is dependent on the availabi [more...]
Jul 29, 2019
A Slippery Slope: Soil Carbon Destabilization
Carbon gain or loss depends on the balance between competing biological, chemical, and physical reac [more...]
Jul 15, 2019
Field Evaluation of Gas Analyzers for Measuring Ecosystem Fluxes
How gas analyzer type and correction method impact measured fluxes. The Science A side- [more...]
List all highlights (possible long download time)