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Global Modeling (GM) Group
GM Group Members:
Summary of Activities:
UT/LS and Middle Atmosphere Studies
In collaboration with Jiyao Xu ( Chinese Academy of Science), R. Collins ( U. of Alaska ) and C-Y. She (CSU), Anne Smith looked at the impact of breaking gravity waves on sodium density and mixing ratio. Although sodium is a minor constituent in the mesosphere, it can be detected with very high vertical and temporal resolution by sodium resonance lidar. This makes it valuable for diagnosing how trace species evolve in the presence of waves. The study, published in JGR, found that in order to distinguish chemical changes from those due to transport, it is very important to understand the details of density and temperature variations due to propagating and breaking waves.
Smith and J. Xu ( Chinese Academy of Science), in collaboration with H.-L. Liu and R. Roble (HAO), C. Mertens and M. Mlynczak (NASA) and J. Russell ( Hampton U. ), investigated the temporal and seasonal variations of the mesopause altitude and temperature using observations from the SABER instrument on the TIMED satellite. The results show that there is a large degree of variability, especially associated with the diurnal cycle in low latitudes. The daily and monthly average mesopause position is fairly steady except for a large downward displacement in summer middle and high latitudes. The study also found a persistent offset between the Northern and Southern Hemispheres during both summer and winter.
A. Smith and D. Marsh used the ROSE model to investigate the processes that account for the so-called secondary ozone maximum near 100 km. The study finds that there are two factors that play a role, of roughly equal importance: 1) this is the altitude of the highest atomic oxygen number density and 2) the extremely cold temperatures favor the formation of ozone. Smith and Marsh also used the model and OH airglow data from the SABER instrument on the TIMED satellite to investigate variability in OH airglow emission. They found that much of the diurnal variability is due to the diurnal tide. Tides also play an important role in the annual variability.
A. Smith and D. Marsh, in collaboration with D. Pancheva and N. Mitchell (Univ. Bath, UK), M. Mlynczak (NASA) and J. Russell (Hampton U.), investigating tidal variability and its dependence on such factors as planetary waves, background winds, and tide-tide interactions. This study has found a persistent correlation between the semidiurnal tide measured by radar in high northern latitudes and the planetary wave variability in the stratosphere of the southern hemisphere. The planetary waves were observed by the SABER instrument on TIMED. The correlation implies that there is a global scale interection and response between planetary wave and the tide.
In collaboration with ACD visitors K. Matthes (also at Free University of Berlin) and T. Sekiyama (Meteorological Research Institute of Japan), Smith and Marsh are using the ROSE model to investigate the resoponse of the atmosphere to the solar flux variations in the presence of a quasi-biennial oscillation (QBO) in tropical winds. Model integrations demonstrate that the phase of the QBO has a significant effect on the atmsopheric response to the solar flux changes. Analysis is ongoing.
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