Middle atmosphere simulated with high vertical and horizontal resolution versions of a GCM: Improvements in the cold pole bias and generation of a QBO-like oscillation in the tropics

Journal Article · Mon Nov 15 04:00:00 EST 1999 · Journal of the Atmospheric Sciences

DOI:https://doi.org/10.1175/1520-0469(1999)056<3829:MASWHV>2.0.CO;2· OSTI ID:20005464

Hamilton, K; Wilson, R J; Hemler, R S

The large-scale circulation in the Geophysical Fluid Dynamics Laboratory SKYHI troposphere-stratosphere-mesosphere finite-difference general circulation model is examined as a function of vertical and horizontal resolution. The experiments examined include one with horizontal grid spacing of {approximately}35 km and another with {approximately}100 km horizontal grid spacing but very high vertical resolution (160 levels between the ground and about 85 km). The simulation of the middle-atmospheric zonal-mean winds and temperatures in the extratropics is found to be very sensitive to horizontal resolution. For example, in the early Southern Hemisphere winter the South Pole near 1 mb in the model is colder than observed, but the bias is reduced with improved horizontal resolution (from {approximately}70 C in a version with {approximately}300 km grid spacing to less than 10 C in the {approximately}35 km version). The extratropical simulation is found to be only slightly affected by enhancements of the vertical resolution. By contrast, the tropical middle-atmospheric simulation is extremely dependent on the vertical resolution employed. With level spacing in the lower stratosphere {approximately}1.5 km, the lower stratospheric zonal-mean zonal winds in the equatorial region are nearly constant in time. When the vertical resolution is doubled, the simulated stratospheric zonal winds exhibit a strong equatorially centered oscillation with downward propagation of the wind reversals and with formation of strong vertical shear layers. This appears to be a spontaneous internally generated oscillation and closely resembles the observed QBO in many respects, although the simulated oscillation has a period less than half that of the real QBO.

• Research Organization: Princeton Univ., NJ (US)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 20005464
• Journal Information: Journal of the Atmospheric Sciences, Journal Name: Journal of the Atmospheric Sciences Journal Issue: 22 Vol. 56; ISSN 0022-4928; ISSN JAHSAK
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
EARTH ATMOSPHERE
FINITE DIFFERENCE METHOD
GENERAL CIRCULATION MODELS
TROPICAL REGIONS
WIND