Effect of trends of middle atmosphere gases on the mesosphere and thermosphere. Issue 6 (21st June 2013)

• Record Type: Journal Article
• Authors: Qian, Liying; Marsh, Daniel; Merkel, Aimee; Solomon, Stanley C.; Roble, Raymond G.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 6(2013:Jun.)
• Page Start: 3846
• Page End: 3855
• Publication Date: 2013-06-21
• Subjects: long‐term change -- upper atmosphere -- greenhouse gases -- ozone -- global circulation model -- middle atmosphere; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/jgra.50354
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract : [1] We conducted model simulations to examine how changes in concentration of radiatively active trace gases in the middle atmosphere affect long‐term changes in the upper atmosphere. We focused our model study on the impact of increases in carbon dioxide (CO2 ), methane (CH4 ), and water vapor (H2 O), and decreases in ozone (O3 ) between 1983 and 2003. We used both the National Center for Atmospheric Research Whole Atmosphere Community Climate Model and the Thermosphere‐Ionosphere‐Mesosphere‐Electrodynamics General Circulation Model, global mean version, in this study. The model simulations indicate that CO2 is the main forcing mechanism of long‐term changes in the thermsophere, with minor influences from O3, CH4, and H2 O. At 400 km altitude, global mean thermospheric neutral density decreased by ~4.5% due to CO2 forcing alone, whereas it decreased by ~4.8% due to the combined forcing from all four gases. O3 depletion caused cooling in the stratosphere and mesosphere (maximum decrease of 0.5 K) due to reduced absorption of solar ultraviolet radiation, but had nearly no cooling effect in the thermosphere. However, due to thermal contraction in the stratosphere and mesosphere, O3 depletion caused a small decrease in thermospheric neutral density of ~0.25%. Increases in both CH4 and H2 O may slightly warm the upper mesosphere and thermosphere due to increased chemical heating and absorption of solar ultraviolet radiation. Key Points: Ozone depletion has nearly no effect in the thermosphere. CO2 is the main forcing for the long‐term cooling in the thermosphere. O3, CH4 and H2O have minor influences in the thermosphere.