From CedarWiki
Jump to: navigation, search

Global Scale Wave Model (GSWM)


Contact Persons

Web Sites

== Description of Instrument/Model

The Global Scale Wave Model (GSWM) simulates solar diurnal and semidiurnal tides calculated in the Earth's atmosphere using realistic ozone and water vapor forcing. The calculations were done for 4 months (January, April, July, October), where the day assumed was the 15th of each month. The background winds are calculated assuming geostrophic balance between 20-80 km. Above 80 km, they are taken from the Portnyagin and Solov'eva model, and below 20 they are taken from the Groves/MSIS model. The background temperature and density are taken from the MSISE90 model using a solar flux of 120 and an Ap of 4.

The results are only weakly dependent on solar cycle, so the year is arbitrary. The year 1995 was chosen because this was the year that the reference appeared. The diurnal and semidiurnal amplitudes and phases of the neutral temperature, the eastward neutral wind, the northward neutral wind, and the vertical neutral wind are given for 31 altitudes between 0 and 124 km in steps of approximately 4 km. There are 59 geographic latitudes that vary between 87 and -87 in steps of 3 degrees. The tidal results are zonal averages. The results from this set of calculations are now known as GSWM-95 tidal predictions.

The vertical velocity is defined to be 0 at the surface, but other temperature and wind values may be zero with a non-zero phase due to round-off.

These semidiurnal tides update the semidiurnal solar tides in the CEDAR Data Base as sdt and reported in Forbes and Vial (1989). The semidiurnal tides were revised in 6/96 to conform to the description given above. Further revisions to the diurnal and and semidiurnal solar tides (GSWM-98 results) using the GSWM were performed in 1998 to include an updated parameterization of gravity wave drag effects and zonal mean zonal winds and ozone climatologies based on UARS data.

There are two versions of the summary plots that show the amplitudes of the diurnal and semidiurnal solar tides in the eastward wind, the northward wind, the neutral temperature, and the vertical velocity. The first set of plots are in color and the second set are in black and white.


Forbes J.M. and Vial F., Monthly simulations of the solar semidiurnal tide in the Mesosphere and Lower Thermosphere J. Atmos. Terr. Phys., 51, 649-661,1989.
Hagan, M.E., J. M. Forbes, and F. Vial, On modeling migrating solar tides, Geophys. Res. Lett., 22, 893-896, 1995a.
Hagan, M.E., J. M. Forbes, and F. Vial, An updated model of migrating tides in the middle atmosphere: Initial results and measurement comparisons, Proceedings of the Workshop on Wind Observations in the Middle Atmosphere, CNES HQ, Paris France, 1995b.

GSWM-95 Color Summary Plots

GSWM-95 Black & White Summary Plots

Older semidiurnal solar tides

Semidiurnal lunar tides

-Revised 22 Jun 2000 by Barbara Emery