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Marvin A. Geller, Mao-Fou Wu, and Melvyn E. Gelman

Abstract

Individual monthly mean general circulation statistics for the Northern Hemisphere winters of 1978–79, 1979–80, 1980–81, and 1981–82 are examined for the altitude region from the earth's surface to 55 km. Substantial interannual variability is found in the mean zonal geostrophic wind; planetary waves with zonal wavenumber one and two; the heat and momentum fluxes; and the divergence of the Eliassen–Palm flux. These results are compared with previous studies by other workers. This variability in the monthly means is examined further by looking at both time-latitude sections at constant pressure levels and time-height sections at constant latitudes. The implications of this interannual variability for verifying models and interpreting observations are discussed.

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Marvin A. Geller, Mao-Fou Wu, and Melvyn E. Gelman

Abstract

Monthly mean Northern Hemisphere general circulation statistics are presented for the four-year average December, January and February months of the winters 1978–79 through 1981–82. These calculations start with daily maps for eighteen pressure levels between 1000 and 0.4 mb of Northern Hemisphere temperature at 1200 GMT that are supplied by NOAA/NMC. Geopotential height and geostrophic wind are constructed using the hydrostatic and geostrophic relationships, respectively. Fields presented in this paper are zonally averaged temperature, mean zonal wind, and amplitude and phase of planetary waves with zonal wave-numbers 1-3. Diagnostic quantities, such as the northward fluxes of heat and eastward momentum by standing and transient eddies along with their wavenumber decomposition and Eliassen-Palm flux propagation vectors and divergences by the standing and transient eddies along with their wavenumber decomposition, are also given. The observations indicate that polar temperatures in the lower stratosphere are warmer in February than in December or January. Upper stratospheric mean zonal winds are also strongest in December and weakest in February, as is consistent with the thermal wind relationship. Stationary planetary waves are observed to have the largest amplitudes in January. Stationary eddy heat and momentum fluxes and the Eliassen-Palm fluxes from the standing eddies are largest in January. This is consistent with the large amplitude wavenumber 1 in January. The results of this paper are compared with those of several other works.

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Pi-Huan Wang, Siu-Shung Hong, Mao-Fou Wu, and Adarsh Deepak

Abstract

The temporal and spatial variations of the zonally-averaged ozone beating rate in the middle atmosphere on a global scale are investigated in detail based on a model study. This study shows that the mean ozone heating rate calculation can be made in a realistic manner by taking advantage of the existing two-dimensional ozone distribution and including the effect of the sphericity of the earth's atmosphere. The obtained ozone heating rates have also been Fourier-analyzed. The common features of the first three harmonic components which correspond respectively to the annual, semiannual and terannual variations are (1) the local maximum amplitudes are located in the altitude regions between 45 and 57 km; (2) local maximum amplitude can be found in the polar region; and (3) maximum horizontal gradients of the beating rate are concentrated in the high latitudes from 60 to 90°. It is also found that the amplitude of the second Fourier component at the pole is about six times greater than that at the equator.

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Marvin A. Geller, Eric R. Nash, Mao Fou Wu, and Joan E. Rosenfield

Abstract

Monthly mean residual circulations were calculated from eight years of satellite data. The diabatic circulation is usually found to give a good approximation to the residual circulation, but this is not always the case. In particular, an example is shown at 60°S and 30 mb where the diabatic and residual circulations show very different annual variations. Correlations between the vertical component of the residual circulation and temperature and ozone were computed. They indicate that yearly variations of temperatures in the tropics are under dynamical control while at higher latitudes they are under radiative control, except during stratospheric warmings. Interannual variations in seasonal mean temperatures are shown to be under dynamical control everywhere. Correlations between the interannual variations in the seasonal means of the vertical component of the residual circulation and ozone mixing ratios are consistent with what would be expected from the ozone variations being due to differences in the ozone transport, although transport effects cannot easily be distinguished from photochemical effects above the altitude of the ozone mixing ratio peak. Finally, variations in total ozone are examined in comparison with residual circulations variations. A one to two month phase lag is seen in the annual variation in the total ozone at 60°N with respect to the maximum downward residual motions. This phase lag is greater at 60°N than at 60°S. There is evidence at 60°S of a greater downward trend in the mean zonal ozone maxima than there is in the minima. A decreasing trend in the maximum descending motion is seen to accompany the ozone trend at 60°S.

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