OH, HO2, and OH Reactivity Behavior in the Southern San Joaquin Valley during CalNex 2010

CalNex 2010 was an opportunity to study the air chemistry of Bakersfield CA, which has some of the worst air quality in California. During the six-week (May 15 - June 28) field campaign, we measured OH and HO2 by laser-induced fluorescence. OH reactivity, the inverse of the OH lifetime, was also measured. OH measurements were performed two ways - the usual method of alternating the laser wavelength on and off the OH absorption and a second method of periodically adding an OH reactant, akin to the method used by the chemical ionization / mass spectrometry technique. While the OH measurements from these two methods are often very similar, they are not always the same. In addition, OH by both methods is often greater than 105 cm3 at night. There are significant differences in these measurements between a cooler period (May 18 - May 29), when OH, HO2, and OH reactivity were very low, and a warmer period (May 30 - June 28). We discuss these results in the context of OH production and loss and ozone production.