Research

Gas-particle reactions of reactive nitrogen represent an important but variable atmospheric chemical cycle. For example, uptake of N 2 O 5 to aerosol regulates the lifetime of NO x (=NO+NO 2 ) and oxidant burdens in the troposphere. Uptake of N 2 O 5 to chloride-containing aerosol to produce ClNO...

Biogenic VOC from terrestrial vegetation (e.g., isoprene, monoterpenes) and biogenic marine sulfur compounds (e.g., dimethyl sulfide, DMS) undergo rapid nocturnal degradation in the presence of the nitrate radical, NO 3 . Since NO 3 is derived from NO x , an anthropogenic pollutant, these oxidative processes represent an anthropogenic perturbation...

Several regions of the United States, particularly in the west, experience poor air quality during winter meteorological conditions that confine local emissions in shallow layers near the surface. However, different regions have widely different responses to local emissions in the winter. Sparsely populated oil and gas producing regions are subject...

Wildfire frequency and intensity is increasing in western North America, with impacts on regional air quality and climate. The FIREX -AQ initiative is a set of laboratory and field studies designed to provide detailed understanding of the complex emissions and subsequent chemical transformations that define these impacts. Recent measurements at...

Aerosols both scatter and absorb incoming solar radiation, influencing Earth's climate. Recent developments of visible cavity ring-down and photoacoustic instruments have enabled new and detailed understanding of ambient aerosol optical properties. We have undertaken the development of broadband aerosol extinction (= absorption + scattering) at short wavelengths using cavity enhanced...

Direct absorption spectroscopy is an absolute technique for measurement of atmospheric trace gases and aerosol extinction that has been traditionally limited in atmospheric science applications because of its low sensitivity. Optical cavities (e.g., two mirrors aligned such that light makes multiple reflections between them) greatly enhance the sensitivity and utility...