Sources of nitrate and ozone in the marine boundary layer of the tropical North Atlantic

Abstract

Daily averaged values in the winter and spring often fall in the range of 25-35 ppbv for periods of several days, and they seldom fall below 20 ppbv. In contrast, during the summer, values typically fall in the range of 10-20 ppbv. During the winter-spring period, there is a very strong negative correlation between O3 and a number of aerosol species, including NO3-. These anticorrelations appear to be driven by changing transport patterns over the North Atlantic as opposed to chemical reactions involving O3 and nitrogen species in the atmosphere. Analyses of isentropic trajectories clearly show that high O3 and low NO3- are associated with transport from higher latitudes and high altitudes. Conversely, high NO3- and relatively low O3 are associated with transport from Africa. Our study suggests that North America and the middle troposphere (and stratosphere) are not strong sources for NO3- over the tropical North Atlantic. -from Authors