Growth of upper tropospheric aerosols due to uptake of HNO3

[摘要] The effect of nitric acid on the equilibrium sizedistributions of upper troposphericaerosols is calculated as a function of relative humidity.It is shown that HNO₃ concentrations above a few tenths of a ppb cancause substantial increases in haze mode particle concentrationsat relative humidities at about 60% and above. The effect can bestrongly magnified when letovicite particles are present in additionto sulfuric acid aerosols. Letovicite particles are less acidic thanthe sulfuric acid particles and so more nitric acid can be absorbed.This effect can be seen even at RH below 50% due to the lowering of thedeliquescence RH of letovicite in the presence of gaseous nitric acidat low temperatures. We have also compared equilibrium calculationsof the HNO₃ effect with observations of increasedhaze mode concentrations at relative humidities above 50%(Petzold et al., 2000). Nitric acidmixing ratios on the order of 0.5-2ppb may explainthe observed increase of haze mode particles atleast partially.

[学科分类] 大气科学