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- Author or Editor: Joan E. Rosenfield x
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Abstract
The global diabatic circulation is computed for the months of January, April, July and October over the altitude region 100 to 0.1 mb using an accurate troposphere-stratosphere radiative transfer model, SBUV and SME ozone data, and NMC temperatures. There is high correlation between the level of wave activity and the local departure of the atmosphere from radiative equilibrium. For example, the summer lower stratosphere is close to radiative equilibrium while the winter is not. We find much greater heating in the upper stratosphere at low latitudes in the summer hemisphere, and roughly a factor of two less heating in the lower stratosphere at low latitudes, than did Murgatroyd and Singleton. An excess in the globally averaged net stratospheric heating from 40 to 50 km is computed for all months, and a deficit from 50 to 60 km is computed during solstice. Roughly a 20% uniform reduction in ozone from 40 to 50 km, or a temperature perturbation with an increase of 5 K at 1 mb, will bring the atmosphere into global radiative equilibrium without significant impact on the diabatic circulation. In the transitional mouths of April and October, the net heating in the fall hemispheres are very similar, while substantial differences exist between the spring hemispheres.
Abstract
The global diabatic circulation is computed for the months of January, April, July and October over the altitude region 100 to 0.1 mb using an accurate troposphere-stratosphere radiative transfer model, SBUV and SME ozone data, and NMC temperatures. There is high correlation between the level of wave activity and the local departure of the atmosphere from radiative equilibrium. For example, the summer lower stratosphere is close to radiative equilibrium while the winter is not. We find much greater heating in the upper stratosphere at low latitudes in the summer hemisphere, and roughly a factor of two less heating in the lower stratosphere at low latitudes, than did Murgatroyd and Singleton. An excess in the globally averaged net stratospheric heating from 40 to 50 km is computed for all months, and a deficit from 50 to 60 km is computed during solstice. Roughly a 20% uniform reduction in ozone from 40 to 50 km, or a temperature perturbation with an increase of 5 K at 1 mb, will bring the atmosphere into global radiative equilibrium without significant impact on the diabatic circulation. In the transitional mouths of April and October, the net heating in the fall hemispheres are very similar, while substantial differences exist between the spring hemispheres.
Abstract
Using a stratospheric-tropospheric data assimilation system, referred to as STRATAN, a minor sudden stratospheric warming that occurred in January 1989 is investigated. The event had a maximum influence on the stratospheric circulation near 2 hPa. The zonal mean circulation reversed briefly in the polar region as the temperature increased 34 K in 3 days. The cause of the warming is shown to be the rapid development and subsequent movement of a warm anomaly, which initially developed in the midlatitudes. The development of the warm anomaly is caused by adiabatic descent, and the dissipation by radiative cooling. A brief comparison with the NMC analysis and temperature sounding data is also presented.
Abstract
Using a stratospheric-tropospheric data assimilation system, referred to as STRATAN, a minor sudden stratospheric warming that occurred in January 1989 is investigated. The event had a maximum influence on the stratospheric circulation near 2 hPa. The zonal mean circulation reversed briefly in the polar region as the temperature increased 34 K in 3 days. The cause of the warming is shown to be the rapid development and subsequent movement of a warm anomaly, which initially developed in the midlatitudes. The development of the warm anomaly is caused by adiabatic descent, and the dissipation by radiative cooling. A brief comparison with the NMC analysis and temperature sounding data is also presented.
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.
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.
