Global tropospheric measurements of mitric acid vapor and particulate nitrate

Measurements of HNO 3 vapor and particulate NO 3 − were made over continental and marine areas, at altitudes from .2 to 7 km, as a part of Project Gametag. HNO 3 vapor was found to be as common over marine areas, far from anthropogenic sources of NO x , as over remote continental regions, ranging from < .02 to .3 ppbv. Urban influenced continental values ranged from .3 to .86 ppbv. Comparable HNO 3 was found both above and within the boundary layer, in contrast to theoretical predictions of a negative HNO 3 gradient with altitude. In many regions of the troposphere there was more HNO 3 vapor than participate NO 3 − , although the reverse is true in the marine boundary layer, where it appears that heterogeneous chemistry converts HNO 3 and Cl − to HCl and particulate NO 3 − . This rather limited data set suggests an HNO 3 lifetime on the order of a few days.