Comparison of a photochemical model with observations of mesospheric hydroxyl and ozone

Abstract

[1] We present a comparison of a photochemical model with mesospheric hydroxyl (OH) data from the Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER) and mesospheric ozone (O 3 ) data from the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER). Although SHIMMER and SABER do not measure the atmosphere coincidently, by sampling the photochemical model at the appropriate local time of each measurement, an effective concurrent test of mesospheric odd oxygen and odd hydrogen theory can be achieved. Consistent with previous, more limited analyses of SHIMMER data, we find no evidence of a systematic model overprediction of mesospheric OH. However, at 80 km, the standard chemical scheme shows a model deficit in the morning hours and a dramatic model excess in the late afternoon. Using a higher rate coefficient for the H + O 2 + M ! HO 2 + M reaction ameliorates this problem. Such a higher rate is consistent with the only reported laboratory measurements at the low temperatures appropriate to the mesosphere. Regarding the SABER ozone, the model significantly underpredicts the data. Some of this could be explained by a previously reported, systematic high bias to the SABER ozone, and comparisons of our model with Microwave Limb Sounder data support that suggestion. Nonetheless, a persistent model ozone deficit remains. Since the model agreement with SHIMMER OH is generally very good, this model ozone deficit is unlikely to be due to a mischaracterization of mesospheric HOx.

Influence of Atmospheric Solar Radiation Absorption on Photodestruction of Ions at D-Region Altitudes of the Ionosphere

“…The use of a theoretical onedimensional neutral atmospheric composition model is the simplest way to estimate number densities of neutral species in the atmosphere (Ogawa and Shimazaki 1975;Fishman and Crutzen 1977;Kasting and Donahue 1980;Prather 1981;Rodrigo et al 1986;Zommerfelds et al 1989;Clancy et al 1994;Swaminathan et al 1998;Zhu et al 2007;Khosravi et al 2013;Shapiro et al 2013;Siskind et al 2013). One of such theoretical models described in Appendix 1 is developed in this work to estimate the ozone number density in the atmosphere.…”

Implications of odd oxygen observations by the TIMED/SABER instrument for lower D region ionospheric modeling

“…Regarding systematic errors, to the extent that there are biases in any of these inputs, these will propagate through to the retrieved [O]. For example, we have shown (Siskind et al, 2013) that it is likely that SABER ozone is too high in the lower mesosphere. This conclusion was reached indirectly by comparing a photochemical model separately with SABER ozone and Aura Microwave Limb Sounder ozone.…”

“…There is a comprehensive literature (see e.g. Siskind et al, 2013 and references therein) whereby photochemical models have been compared with mesospheric ozone and generally fail to completely reproduce the observed abundances. Since the models typically fall below the observations this discrepancy has historically been termed the ozone deficit problem and is important considering ozone's central importance to middle atmospheric structure and climate.…”

Stratospheric and mesospheric HO<sub>2</sub> observations from the Aura Microwave Limb Sounder

“…However, Canty et al (2006) concluded that, at least between 25 and 60 km, the HO x Microwave Limb Sounder (MLS) and FIRS-2 observations were reasonably well described by photochemical models. In addition to these modelling discrepancies (a problem known as the HO x dilemma), models have consistently underpredicted the amounts of O 3 at such altitudes, an issue known as the O 3 deficit problem (Crutzen and Schmailzl, 1983;Solomon et al, 1983;Eluszkiewicz and Allen, 1993;Summers et al, 1997;Varandas, 2004;Siskind et al, 2013).…”