ENHANCED FORMATION AND DEVELOPMENT OF SULFATE PARTICLES DUE TO MARINE BOUNDARY-LAYER CIRCULATION

Production and the subsequent development of sulfur-derived particles in the marine boundary layer have been of great interest due to their potential role in modifying the radiative properties of marine stratiform clouds. In this work these phenomena were studied using a dynamic air parcel model, with the emphasis placed on examining how the boundary layer dynamics affects the system. Our simulations suggest that a homogeneous or steady boundary layer assumption may lead to a considerable underestimation of the number of nuclei formed. Further, we showed that if the observed particle size distributions and nonsea-salt fraction of cloud condensation nuclei (CCN) production are to be explained by ii; situ particle production and growth, the sulfuric acid accommodation coefficient onto nuclei must be greater than 0.1 under conditions typical for clean marine areas. These high values require either a sulfuric acid vapor source in addition to SO2(g) oxidation or a H2SO4(g) accommodation coefficient onto more aged particles which is less than that onto nuclei. Both these options were tested and can be considered viable based on our present understanding of the marine environment. Finally, we showed that a nighttime interaction of the boundary layer air with clouds does not significantly affect nuclei formation or growth, but may lead to significant scavenging of fresh nuclei if their sulfuric acid accommodation coefficient is small. Cloud interactions during photochemically active periods may completely inhibit new particle production, and the growth of preexisting nuclei is likely to be significantly decelerated.