A new NASA-led study helps answer decades-old questions about the role of smoke and human-caused air pollution on clouds and rainfall. Looking specifically at deep convective clouds -- tall clouds like thunderclouds, formed by warm air rising -- the study shows that smoky air makes it harder for these clouds to grow. Pollution, on the other hand, energizes their growth, but only if the pollution isn't heavy. Extreme pollution is likely to shut down cloud growth.
A new NASA-led study helps answer decades-old questions about the role of smoke and human-caused air pollution on clouds and rainfall. Looking specifically at deep convective clouds -- tall clouds like thunderclouds, formed by warm air rising -- the study shows that smoky air makes it harder for these clouds to grow. Pollution, on the other hand, energizes their growth, but only if the pollution isn't heavy. Extreme pollution is likely to shut down cloud growth.
Researchers led by scientist Jonathan Jiang of NASA's Jet Propulsion Laboratory in Pasadena, California, used observational data from two NASA satellites to investigate the effects of smoke and human-made air pollutants at different concentrations on deep convective clouds.
The two satellites -- the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat -- orbited on the same track only a few seconds apart from 2006 until this year. CloudSat uses a radar to measure cloud locations and heights worldwide, and CALIPSO uses an instrument called a lidar to measure smoke, dust, pollution and other microscopic particles in the air, which are collectively referred to as aerosols, at the same locations at almost the same time. The combined data sets allow scientists to study how aerosol particles affect clouds.
CALIPSO is able to classify aerosols into several types, a capability which was improved two years ago when the CALIPSO mission team developed improved data-processing techniques. At about the same time, the CloudSat team also improved its classification of the cloud types. Jiang's team knew that these improvements had the potential to clarify how different aerosols affect the ability of clouds to grow. It took him and his colleagues about two years to go through both data sets, choose the best five-year period and Earth regions to study, and do the analysis.
Read more at NASA JPL - California Institute of Technology
Image: Heavy human-caused pollution can suppress the growth of rain-producing clouds. (Credit: Jack French/CC BY-NC 2.0)
