Cloud chemistry research at Whiteface Mountain

Cloud collection principles are briefly reviewed; the performance of two collectors in common use is compared. Two cloud event studies (one during winter, the other during summer) are presented to contrast typical time-dependent histories of chemical concentrations for the two seasons. During winter, the oxidation rate of SO(2) is low, resulting in measured sulfate concentrations independent of SO(2) concentrations. During summer, SO(2) is rapidly oxidized by H(2)O(2) with a residue of H(2)O(2) persisting in cloud water after SO(2) has been converted. Changes in the gas phase concentrations of SO(2) and H(2)O(2) are shown during a cloud event. Both gases drop to very low concentrations in cloud with H(2)O(2) tending to recover after available SO(2) has been oxidized. The meteorology for each event is presented to illustrate the role of atmospheric structure in the transporting of emitted material and in determining cloud water compositions. Finally, a cloud chemistry climatology for winter and summer is presented, based upon 6 years of observations at Whiteface Mountain.