Dynamical processes in the middle atmosphere as observed from Upper Atmosphere Research Satellite limb-sounding data

• Main Author: Allen, Douglas Ray
• Format: Text
• Language: English
• Published: Iowa State University Digital Repository 1997
• Subjects: Physics and astronomy; Physics; Atmospheric Sciences; Arctic
• Online Access: https://lib.dr.iastate.edu/rtd/11767; https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=12766&context=rtd

This study uses data from the Upper Atmosphere Research Satellite (UARS) to investigate two topics in middle atmosphere dynamics: the "4-day wave" and transport processes deduced from atmospheric carbon monoxide. The 4-day wave is an eastward moving quasi-nondispersive feature with 4 day period occurring near the winter polar stratopause. Evidence of the 4-day feature is presented in UARS Microwave Limb Sounder (MLS) temperature, geopotential height, quasigeostrophic potential vorticity (PV), and ozone from the late southern winters of 1992 and 1993. Space-time spectral analyses reveal a double-peaked vertical temperature structure with an out-of-phase relationship between the two peaks. The height variation of the 4-day ozone signal compares well with a linear advective-photochemical tracer model. Regions of negative PV gradient and positive Eliassen-Palm flux divergence are shown to occur, consistent with instability dynamics playing a role in wave forcing. The three-dimensional wave structure resembles the PV "charge" concept, wherein a PV anomaly in the atmosphere (analogous to an electrical charge in a dielectric material) induces a geopotential field, a vertically oriented temperature dipole, and circulation about the vertical axis;Observations of carbon monoxide in the upper stratosphere and lower mesosphere from the UARS Improved Stratospheric and Mesospheric Sounder (ISAMS) are presented during the early northern winter 1991/1992. High CO mixing ratios are found to saturate the polar vortex. 2D analyses in the meridional plane indicate: (1) Increasing mixing ratio with altitude. (2) Large mixing ratios near the Arctic winter pole due to downward advection from the diabatic circulation. (3) A tropical upper stratosphere maximum likely due largely to methane oxidation. ISAMS CO data are compared with CO output from a 3D chemistry and transport model (CTM), initialized with ISAMS CO. ISAMS and CTM horizontal distributions compare favorably near the stratopause, while disagreement in the vertical zonal mean CO distributions occurs several weeks into the model run, with CTM mixing ratios biased high in the upper stratosphere outside the polar vortex and low in the stratospheric vortex and lower mesosphere. Novel modified Lagrangian mean diagnostics applied to ISAMS and CTM data provide insight into horizontal mixing processes during a rapid merger of two anticyclones.