The Dependence of Tropospheric Hydroxyl Content on the Alignment Between the NO_x and CO Total Emissions

Abstract

Many theoretical studies testify to an exceptionally important role of OH radical in the tropospheric chemistry (Crutzen, Zimmermann, 1991; WMO/UNEP, 1999; etc.). Due to its extremely high reactivity, OH controls or essentially influences the content of many tropospheric species, such as carbon monoxide CO, methane CH₄, ozone O₃, nitrogen oxides and others. Simultaneously, these species determine the behavior of tropospheric OH. As a result of their chemical interactions, the quantitative estimations of tropospheric hydroxyl concentration were calculated by the models of different complexity (e.g. Lelieveld et al., 1998; Wang, Jacob, 1998; Kiselev, Karol, 1999, 2000a). But it is difficult to validate them by the relevant observations, as there is presently no instrumentation for regional to global scale those of tropospheric OH (Brasseur, Prinn, 2000). Thus, the regular monitoring of tropospheric OH is not yet established and there are a few its isolated measurements only (e.g. Kleinman et al., 1998; Brune et al., 1999). Under the circumstances modeling is a basic tool of study of tropospheric OH chemistry. Up to now there is no common opinion among the specialists about the evolution of tropospheric OH, and the modern model reconstructions of its trend differ not only in magnitude but in sign. According to Martinerie et al. (1995), Kiselev, Karol (2000a) the tropospheric OH content has been increasing last 150 years but other studies (e.g. Lelieveld et al. (1998), Chappellaz et al. (1993)) evaluate the drop of tropospheric OH in the same period.