ATMOSPHERIC MEASUREMENTS OF AEROSOL PRECURSOR GASES IN THE UPPER TROPOSPHERE AND LOWER STRATOSPHERE

Our measurements cover winter and summer conditions and middle as well as polar latitudes. Sulfur dioxide (SO2) was found to be mostly around several hundred parts per trillion by volume (pptv) in the upper troposphere. Occasionally very strong SO2-pollution was observed in extended upper tropospheric air masses. Probably this was caused by fast upward transport from the polluted continental boundary layer. Gaseous sulfuric acid (H2SO4) ranged between 1 × 105 and 5 × 10 6 molecules per ccm (0.01-0.5 pptv) and was mostly positively correlated with SO2. This reflects expected H2SO4-formation from SO2. The abundance ratio H2SOdSO2 was mostly around 0.001-0.002. Nitric acid ranged between 100 and 10 000 pptv. The largest HNO3 was observed in the lower arctic stratosphere in winter. However even in the upper troposphere nitric acid reached occasionally 3 000 pptv. Probably the latter was due to rapid vertical transport from the polluted continental boundary layer. Gaseous ammonia decreases very steeply above about 5 km Around 8 km altitude the NH3 number density is only of the order of 1×106 cm 3 corresponding to an atmospheric volume mixing ratio of 0.1 pptv. Measurements were also made in wakes of jet air liners at cruise altitudes and in jet engine exhaust at the ground. Here SO2, SO3, H2SOa, HNO2 and HNO3 were detected. Evidently