Abstract
Abstract. This Technical Note presents a statistical approach to evaluating simultaneous measurements of several atmospheric components under the assumption of photochemical equilibrium. We consider simultaneous measurements of OH, HO2, and O3 at the altitudes of the mesosphere as a specific example and their daytime photochemical equilibrium as an evaluating relationship. A simplified algebraic equation relating local concentrations of these components in the 50–100 km altitude range has been derived. The parameters of the equation are temperature, neutral density, local zenith angle, and the rates of eight reactions. We have performed a one-year simulation of the mesosphere and lower thermosphere using a 3-D chemical-transport model. The simulation shows that the discrepancy between the calculated evolution of the components and the equilibrium value given by the equation does not exceed 3–4 % in the full range of altitudes independent of season or latitude. We have developed a statistical Bayesian evaluation technique for simultaneous measurements of OH, HO2, and O3 based on the equilibrium equation taking into account the measurement error. The first results of the application of the technique to MLS/Aura data (Microwave Limb Sounder) are presented in this Technical Note. It has been found that the satellite data of the HO2 distribution regularly demonstrate lower altitudes of this component's mesospheric maximum. This has also been confirmed by model HO2 distributions and comparison with offline retrieval of HO2 from the daily zonal means MLS radiance.
Highlights
A prominent feature of atmospheric photochemical systems is the presence of a large number of chemical components with short lifetimes and concentrations close to stable photochemical equilibrium at every instant
This assumption is supported by the calculation of the HO2 distributions with the use of our 3-D chemical transport model
It can be seen that the mesospheric maximum of HO2 in these months, as well as of the < HOr2et > distributions lies above 0.046 mbar
Summary
A prominent feature of atmospheric photochemical systems is the presence of a large number of chemical components with short lifetimes and concentrations close to stable photochemical equilibrium at every instant. The condition of balance between their sources and sinks is described by a system of algebraic equations This system can be used to determine characteristics of hard-to-measure atmospheric species through other measurable components, evaluate results of remote or in situ measurements, estimate reaction rates usually known with significant uncertainty, and to understand processes and chemical reactions that influence the variability in the most important atmospheric components, e.g., ozone, in the geographical region of interest. Algorithms for retrieving distributions of OH and HO2 from the satellite measurement data of O3, NO2, H2O, HNO3 by LIMS/Nimbus-7 and UARS with the help of algebraic models following from the photochemical equilibrium of Ox, HOx, and HNO3 components were proposed by Pyle and Zavody (1985) and Pickett and Peterson (1996). The last section contains a discussion of the results followed by concluding remarks
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