Wintertime cloud chemistry

The results presented here were obtained during the wintertime phases of the Atmospheric Sciences Research Center (ASRC) cloud chemistry research program at the summit of Whiteface Mt. Data obtained during the last two winters are the only monitoring data of supercooled cloud water so far available. The observations which follow from this work should apply generally to the mid-troposphere over a region at least as large as the northeastern U.S. whenever the chemistry is not dominated by urban or industrial plumes. SO/sub 2/ and NO/sub X/ both have substantially higher concentrations during winter. While SO/sub 2/ is rapidly oxidized to SO/sub 4//sup 2 -/ in summer clouds, it is not able to undergo rapid oxidation in the liquid phase during winter. This is attributed to the absence of a strong oxidant such as H/sub 2/O/sub 2/. The most abundant inorganic anion in wintertime clouds tends to be NO/sub 3//sup -/, whereas SO/sub 4//sup 2 -/ is generally the dominant anion during the summer. From observations it can be concluded that wintertime cloud chemistry is limited by unavailability of sufficient oxidant (H/sub 2/O/sub 2/). Thus, a major part of the year has been identified where the atmospheric system is strongly non-linearmore » for SO/sub 2/.« less