Supercooled cirrus cloud formation modified by nitric acid pollution of the upper troposphere



We have investigated nitric acid induced cirrus cloud formation in the upper troposphere. Our theoretical model investigations were made in the light of recent upper tropospheric gaseous nitric acid observations which show higher than expected nitric acid abundances. Our investigations indicate markedly increased cloud condensation nuclei number densities due to nitric acid induced aerosol activation. Our findings suggest that nitric acid may substantially modify supercooled cirrus cloud formation at temperatures above −40°C and thereby influence climate.