Dave Covert

Research Scientist

DaveDavid Covert, research faculty with the University Of Washington Department of Atmospheric Sciences, studies the physical, optical and chemical properties of aerosols, particles suspended in air, and their effects on clouds and climate. The research is largely based on observations, which involves developing instruments and systems of instruments for measuring these particles and then using them in field experiments (ranging from Tasmania to northern Norway, and Monterey, California to New Hampshire). These suspended particles, which range in size from 1/100th of a millimeter diameter, about that of a human hair, to 1000 times smaller, are found in the atmosphere as a result of geological, biological and anthropogenic sources. Wind blown dust, volcanic emissions, sea spray are among the geological sources. Pollen, yeasts and bacteria, emissions from vegetation and naturally occurring forest or grass fires are some of the biological sources. These are largely naturally occurring particles and have been part of the earth system for millennia. In addition, and what we now encounter most often in and downwind of our urban centers, are the particles from anthropogenic sources. These include combustion from electric power plants, vehicle exhaust and metal smelting for example, and are commonly referred to as air pollution, or in extreme cases, smog.

The particles accumulated from all these sources have effects on our atmosphere, weather and climate, and on human health. The effects on climate have to do with how much sunlight is intercepted and either absorbed by the particles, or reflected back to space by them. If the sunlight is absorbed by the particles, both the particles themselves, and the air surrounding them, are warmed. The 'sooty', black particles, e.g. exhaust from rich diesel exhaust, absorb light and warm the atmosphere around them relative to what would happen in their absence. 'White' particles, e.g., sea salt or sulfuric acid from sulfur dioxide emissions, scatter light, some of which returns to space, thus cooling the earth-atmosphere. This also reduces visibility—our ability to see distant objects. Clearly there are all grades of particle in between these white and black extremes, (gray or brown particles). These particles can also act to form cloud and fog droplets, increasing the 'thickness' of fog or clouds. In meteorological terms this can affect the extent of a cloud and how long it lasts, (where, and how much, rain or snow falls from it).

Observational research in this area involves collecting particles by the billions, determining how many are in a given volume of air, how big they are, what they are made of chemically, and how they interact with visible and infrared radiation. Field experiments involving collaboration between dozens of scientists from universities and research laboratories in the US and other countries are organized to focus on specific problems and geographical areas, using land stations, towers, mountain top observatories, photo of bridge deck on shipresearch ships and aircraft. Recent field experiments included a ship borne study east of Japan, Korea and China to characterize aerosol in the plume from the Asian continent, and a study along the US Gulf of Mexico coast to study the relatively clean marine air, the dust plume from the Sahara Desert, and the urban-industrial plumes from the Houston, Galveston area.

The results are used to determine if air pollution control strategies are effective, to test the validity of global and regional air pollution and atmospheric chemistry models, and as quantitative input to climate models which predict the effect of "greenhouse" gases and particles on global temperature and weather patterns.

David has a BS in Chemistry, 1970, which was followed by a master’s degree in engineering from the Water and Air Resources Division of Civil Engineering. A doctoral degree was earned in the same department on the topic of atmospheric chemistry via interdisciplinary studies between chemistry, atmospheric sciences and engineering. His career has developed from this educational base. For two decades he has conducted studies on the pulmonary health effects of air pollution with a research group in the Department of Environmental Health at the University of Washington. David continued collaboration with the atmospheric and oceanographic science communities during this time. In 1993 his position was shifted to the Department of Atmospheric Sciences and he focused on his research on atmospheric aerosol properties. The common thread is that the effects of air pollution particles on the both health and climate are determined by their chemistry and physics, and detailed, accurate measurements of these particulates are needed in both disciplines.

When he is not chasing and characterizing particles, David enjoys bicycling, hiking, cross-country skiing, and small boats, according to the season - anything to get outdoors and watch the weather. His children are grown, one is a chemical oceanographer at NOAA PMEL in Seattle, another, an administrative assistant at an energy startup company in Seattle and the third is studying in Vienna to be a diplomat in the EU.