Atmospheric Gravity Waves

Critical Level Directional Filtering of Atmospheric Gravity Waves:
A Comparison of OH Airglow Observations and a Wind Profile Model

Synopsis
Thesis involved computing the magnitude and direction of atmospheric gravity waves subject to blocking by horizontal winds, i.e. critical layer directional filtering. To accomplish this, a wind profile model was developed using the latest climatological background winds and numerical models of tidal modes. Data from the wind profiles was then analyzed to determine blocking diagrams, which show the forbidden directions and phase velocities of wave propagation at a given height. The blocking diagrams were then compared with experimental observations of gravity waves in airglow to determine the accuracy of the wind profiles and help explain critical layer theory.

Wind Profiles

December Zonal and Meridional Local Midnight	All Months Zonal Local Midnight	All Months Meridional Local Midnight	December Zonal and Meridional Background + Tides(@LM)

SlideShow varying Month.

Blocking Diagrams

December 85 km Local Midnight	All Months 85 km Local Midnight	May 80-100 km Local Midnight	August 80-100 km Local Midnight

SlideShow varying Month and/or Height.

References

Occurrence Characteristics of Mesospheric Gravity Waves at 51N, D.H. Geirs, Y. Sahai, L.L. Cogger, E.H. Ryan, J. of Atmospheric and Solar-Terrestrial Physics, 59 (10), 1197-1203, 1997. (doi:10.1016/S1364-6826(96)00117-4)

Evidence of Preferential Directions for Gravity Wave Propagation Due to Wind Filtering in the Middle Atmosphere, M.J. Taylor, E.H. Ryan, T.F. Tuan, and R. Edwards, J. of Geophys. Res., 98 (A4), 6047-6058, 1993. (doi:10.1029/92JA02604) (doi:10.1029/92JA02604)

Response of the Hydroxyl Layer to Small Vertical Scale Gravity Waves Propagating in a Realistic Windy Atmosphere, U.B. Makhlouf, R.H. Picard, J.W. Winick, T.F. Tuan, E.H. Ryan, 1993 Fall Meeting, Eos, Transactions, AGU, 74 (43), October 26, 1993, (SA31A-08).

Effects of Wind Filtering on OH Airglow Observations of Gravity Wave Propagation, M.J. Taylor, E.H. Ryan, T.F. Tuan, 1991 Fall Meeting, Eos, Transactions, AGU, 72 (44), October 29, 1991, (SA51A-07).

Critical Level Directional Filtering of Atmospheric Gravity Waves: A Comparison of OH Airglow Observations and a Wind Profile Model, Edward H. Ryan, M.S. Thesis, University of Cincinnati, September 1991. (Abstract)