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Search for Atmospheric Tides in the CMIP3 (a.k.a. IPCC AR4) and AMIP Archives of GCM Output

PI: Curt Covey
Institution: Lawrence Livermore National Laboratory
Additional Investigators: Richard S. Lindzen
Abstract:
Atmospheric tides driven by solar heating are readily detectable at Earth's surface; in the middle and upper atmosphere they attain large amplitudes and can be the most significant part of atmospheric motion. We propose to examine the 3-hourly CMIP3 GCM output for thermal tides. If we find a tidal signal in the CMIP3 output, we will consider studying high-frequency GCM output archived by AMIP as well. The AMIP data includes 6-hourly wind velocity at 850 and 200 hPa levels as required fields, and at 50 hPa as an optional field. To the best of our knowledge, no other CMIP or AMIP projects have studied atmospheric tides.

Early observations revealed that the semi-diurnal component is a prominent part of the surface response even though it is generated primarily in the middle atmosphere. In addition to the presence of tides, the phase of the semidiurnal tide is a particularly interesting indicator. Climate-oriented GCMs traditionally concentrate on the lower atmosphere, with the stratosphere and higher levels poorly resolved, but many of the CMIP3 models extend up to or above the 1 hPa level and some may have adequate (~5 km) resolution in the stratosphere. We will see if these model characteristics correlate with the ability to simulate atmospheric tides.

If some GCM output does appear to give reasonable simulation of the tides, then we may want to entrain Aiguo Dai from NCAR into this project. A quick literature search implies that he wrote the definitive account of the diurnal and semidiurnal tide signals in observed global surface pressure fields (JAS 56: 3874, 2003).

References:

Chapman, S. and R. S. Lindzen, 1970: Atmospheric Tides: Thermal and Gravitational, Gordon & Breach Publishers

Hagan, M. E., J. M. Forbes and A. Richmond, 2003: Atmospheric Tides, in the Encyclopedia of Atmospheric Sciences, ed. J. R. Holton, Academic Press
Publications:
  • Covey, Curt, Aiguo Dai and Richard S. Lindzen, Atmospheric Tides Simulated by WACCM-1 and CMIP3 / IPCC Climate Models. EOS. Submitted. Abstract. Edit.
  • Covey, Curt, Aiguo Dai, Dan Marsh, Richard S. Lindzen, 2011: The Surface-Pressure Signature of Atmospheric Tides in Modern Climate Models. J. Atmos. Sci., 68, 495514, 10.1175/2010JAS3560.1. Abstract. Edit.

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