Iterative bulk exchange model for estimating air‐water transfer of HNO₃

Air‐water exchange rates have been estimated for most nitrogen species over open ocean; however, these rates may not apply to coastal areas due to different meteorological conditions. In coastal areas the primary obstacle to estimating the exchange rate has been the lack of near‐surface, over‐water meteorological data for mesoscale model input. To address this need, a network of buoys has been deployed in Chesapeake Bay. The two objectives of this project were (1) to develop and evaluate an iterative bulk exchange model to estimate air‐water exchange of heat, water, and momentum from buoy data and (2) to use the model outputs to estimate air‐water transfer rates of nitric acid (HNO 3 ). In a previous study a similar approach to that used in this study was applied to sulfur dioxide (SO 2 ). The analyses performed in this study demonstrate the need to determine if variability in HNO 3 concentration is significantly correlated with the corresponding variability in transfer rate to Chesapeake Bay. The theoretical limitations associated with this approach were lack of homogeneous conditions in the coastal zone and the inadequacy of similarity theory to describe turbulent conditions measured. The approach used in this study should be applicable to other hygroscopic chemicals in addition to HNO 3 and SO 2 (e.g., ammonia).