Geophysical Research Letters · 1994 · 78 citations · 12 references
Natural SciencesChemistryEarth SciencesAtmospheric ChemistryAtmospheric ScienceEnvironmental ChemistryAtmospheric Oxidation ProcessesAtmospheric Radical ChemistryNitrogen OxidesOzone ChemistryStratospheric ChemistryTropospheric ChemistryDiurnal BehaviorHydrolysisIn-situ MeasurementsPhotochemical ProcessesPhotochemical ProductionPhotolysis ProcessesStratospheric AerosolsStratospheric Radical Chemistry
In situ measurements of hydrogen, nitrogen, and chlorine radicals obtained through sunrise and sunset in the lower stratosphere during SPADE are compared to results from a photochemical model constrained by observed concentrations of radical precursors and environmental conditions. Models allowing for heterogeneous hydrolysis of N 2 O 5 on sulfate aerosols agree with measured concentrations of NO, NO 2 , and ClO throughout the day, but fail to account for high concentrations of OH and HO 2 observed near sunrise and sunset. The morning burst of [OH] and [HO 2 ] coincides with the rise of [NO] from photolysis of NO 2 , suggesting a new source of HO x that photolyzes in the near UV (350 to 400 nm) spectral region. A model that allows for the heterogeneous production of HNO 2 results in an excellent simulation of the diurnal variations of [OH] and [HO 2 ].
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