Asatellite technique to better estimate con- centrations of pollutants, such as soot, through cloud cover has been developed by University of Iowa (UI) scientists, the university said in a statement.

Clouds block remote-sensing satellites’ ability to detect, and thus calculate, the concentration of pollution nearer to the ground. This includes particles (commonly known as soot), which reduce the air quality and affect the weather as well as the climate.

UI researchers have developed a new technique to evaluate how aerosol pollutants affect clouds, enabling scientists to examine clouds to determine particle concentrations in the atmosphere below.

“Particles in the atmosphere (aerosols) interact with clouds, changing their properties. With this technique, we can use remote sensing observations from satellites to estimate cloud properties in order to correct predictions of particle concentrations. This is possible, owing to a numerical model that describes these aerosol-cloud interactions,” said UI Center for Global and Regional Research (CGRER) environmental engineering doctoral student and researcher Pablo Saide.

The new technique is expected to find imme- diate application across a range of activities. Examples include air-quality forecasting, numerical weather prediction, climate projections, oceanic and anthropogenic emissions estimations, as well as health-effect studies, added UI College of Engineering co-author and assistant professor of civil and environmental engineering Scott Spak.

“Unlike previous methods, this technique can directly improve predictions of near- surface, fine-mode aerosols, such as coal-fired electricity generating plants and wood-fuelled cooking fires, responsible for human health impacts and low-cloud radiative forcing (solar heating),” said UI CGRER codirector, professor of chemical and biochemical engineering and co-author Greg Carmichael.

“This technique is also complementary to previous methods used, enabling the observing system to ‘see’ aerosols even under cloudy conditions,” he explained.

Existing weather satellites observe warm, single-layer clouds, such as the stratocumulus clouds that form off the west coasts of Africa, North America and South America. These clouds are thought to be the main factors contributing to climate cooling.

Researchers calculate the number of droplets in the clouds using the satellite data, which are then compared to a model estimate provided by the UI programme.

As airborne particles interact with clouds, the model estimates of particles are corrected so that the model generates a better correlation with the satellite number of droplets.

Particles interacting with clouds are usually below clouds, thus, in some cases, the model corrections can be attributed to emissions made by humans.

The researchers conducted their study using National Science Foundation (NSF) aircraft measurements to make simultaneous cloud and particle observations, which verified satellite observations and the mathematical formulas used to determine the pollution concentrations in the air.

The three UI researchers agree their new technique of detecting aerosols through clouds to make ground observations is likely to generate increasing interest, as the need to infer ground-air pollution levels and mitigate human hazards increases.

Paper co-authors also include space agency National Aeronautics and Space Administration Langley Research Center researcher Patrick Minnis and research support company Science Systems & Applications Incorporate researcher Kirk Ayers.

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