Atmospheric and ionospheric response to trace gas perturbations through the ice age to the next century in the middle atmosphere. Part I - Chemical composition and thermal structure

Abstract

The aim of this first part of a series of two articles is to examine the potentially important role of the changing atmosphere on middle atmosphere ionization. The period covered is the last glacial maximum to the middle of the next century. Important parameters of interest to the ionization are changes in temperature and the concentration of several neutrals, especially H₂O, NO_x, H₂SO₄, CH₃CN, aerosols, etc. This part deals with the changes in all these neutrals and the temperature affecting the ionization using an interactive two dimensional model of chemistry, radiation and dynamics. This article constructs an input field for article II which is devoted to changes in the middle atmosphere ionization. For the past, values of the forcing parameters are known whereas, for the future, we assumed scenarios for the forcing parameters and made simulations. Special attention has been given to highlight changes at 30 °N. The two dimensional model used here considers 'frozen' circulation in the troposphere. Although increased thermal emission by perturbing the lower boundary temperature has been considered while simulating for future, it is still a constraint in the present model.