A model calculation of the diurnal variation in minor neutral constituents in the mesosphere and lower thermosphere including transport effects

Abstract

The nonequilibrium calculation for various neutral constituents in the mesosphere and lower thermosphere (Hunt, 1966) was extended by including the effects of molecular and eddy diffusion. Nitrogen and its oxides were added, and more recent laboratory data for chemical reaction coefficients were used. A special numerical technique has been developed to simultaneously solve time‐dependent continuity equations for 14 constituents. The preliminary result indicates that vertical eddy diffusion significantly reduces the irregular variations around 80 km and tends to lower the height of these irregular variations. However, the value of the eddy diffusion coefficient acceptable from the consideration of heat balance below ∼100 km cannot entirely smooth out these irregular distributions for atomic oxygen, ozone, and oxygen‐hydrogen compounds, although the smoothing effect for nitric oxide seems to be strong enough to eliminate the irregular variations above ∼70 km. The role of the transport terms for molecular and eddy diffusion in the continuity equation is illustrated explicitly and discussed for some representative cases. We show that the dynamic model fits the observational results for ozone and nitric oxide concentrations better than the static model and also offers a more adequate explanation for the observed diurnal variation in the OH airglow emission.

Carbon dioxide density and 15.MU. band radiation in the mesosphere and lower thermosphere.

“…In this calculation, the density of O3 near 85 km is-7X107/cm3 and not the value of 108-109/cm3 estimated by SHIMAZAKI and LAIRD (1970), because the density of O becomes noticeably small compared with the SHIMAZAKI and LAIRD model (1970) and this results in a small production rate of O3 by O+O2+M->03+M.…”

“…and LAIRD (1970) pointed out that the second small peak of O2(14g) density is accounted for by the reaction of 03+h1-O2(14 g)+O and O3+0-O2+O2(14g) for the large concentration of O3 estimated by them. In this calculation, the density of O3 near 85 km is-7X107/cm3 and not the value of 108-109/cm3 estimated by SHIMAZAKI and LAIRD (1970), because the density of O becomes noticeably small compared with the SHIMAZAKI and LAIRD model (1970) and this results in a small production rate of O3 by O+O2+M->03+M.…”

“…HAYS and OLIVERO (1970) derived the model assuming O and OH density profiles proposed by HESSTVEDT (1967), however HESSTVEDT had estimated the densities of O and OH using different value of the eddy diffusion coefficient from HAYS and OLIVERO's. Many investigators pointed out that O density was strongly affected by eddy diffusion processes in the lower thermosphere (COLEGROVE et al, 1966;SHIMAZAKI, 1967;HESSTVEDT, 1967;SHIMAZAKI andLAIRD, 1970, 1972;BOWMAN et al, 1970;KENESEA and ZIMMERMAN, 1970;GEORGE et al, 1972;. Therefore it seems necessary to calculate simultaneously the densities of CO2, O, OH and other constituents using same value of eddy diffusion coefficient.…”

A new family Jacobian solver for global three‐dimensional modeling of atmospheric chemistry

“…An atmospheric chemical system is governed by a set of species rate equations, which is normally written as To carry out practical calculations, the earliest and most straightforward explicit approaches for solving atmospheric chemical rate equations were quickly abandoned in favor of numerical implicitness (or semi-implicitness), with or without iterative procedures to stabilize the solutions [e.g., see Shimazaki and Laird, 1970;Turco and Whirten, 1974]. At a given time step, species concentrations could be repeatedly calculated using a simple semi implicit form of (1) by updating the chemical production and loss rates using species concentrations calculated at the previous iteration.…”

“…SFMI thus should allow practical long-term integrations of global chemistry coupled to general circulation and climate models, studies of interannual and interdecadal variability in atmospheric composition, simulations of past multidecadal trends owing to anthropogenic emissions, long-term forecasting associated with projected emissions, and sensitivity analyses for a wide range of physical and chemical parameters. To carry out practical calculations, the earliest and most straightforward explicit approaches for solving atmospheric chemical rate equations were quickly abandoned in favor of numerical implicitness (or semi-implicitness), with or without iterative procedures to stabilize the solutions [e.g., see Shimazaki and Laird, 1970; Turco and Whirten, 1974]. At a given time step, species concentrations could be repeatedly calculated using a simple semi implicit form of (1) by updating the chemical production and loss rates using species concentrations calculated at the previous iteration.…”