Responses of the upper middle atmosphere (60–110 km) to the stratwarms of the four pre-map winters (1978/9–1981/2)

The global developments of the four stratospheric events (～20–50 km) are described, using balloon, satellite and rocket data. Winds data for heights of 60–95 km, derived from L.F. drift (52°N, 15°E; Europe) and M.F. radar (52°N, 107°W; Canada), are then compared with the stratospheric data. There is clear evidence that the preliminary planetary waves often penetrate strongly to ～90 km, and that mean wind reversals also occur. However, there are dramatic differences between European and Canadian mesospheric responses.     

Responses of the upper middle atmosphere (60–110 km), to the first two stratwarms of map (1982/3, 1983/4)

The global developments of the stratospheric events (～20–50 km) are briefly described using balloon and satellite data. Winds data from L.F. drift (52°N, 15°E, Europe) for heights of 90–100 km, and from M.F. radar (52°N, 107°W, Canada) for heights of 60–110 km are then compared with the stratospheric morphology.Data for 1982/3 and 1983/4 show that the planetary wave activity and warmings produced strong westward and southward perturbations in the radar winds. Satellite data from 0.1, 0.01 hPa are consistent with these winds; and also show smaller scale structures in the mesosphere than the stratosphere. The semi-diurnal tide responded strongly to the atmospheric disturbances in Europe and Canada: for the latter vertical wavelength changes occurred for heights of 70–100 km. However the correlation between these tidal fluctuations was not high indicating that the tidal adjustments were continental rather than hemispheric.     

A survey over the PMP-1 winters 1978/79–1981/82 in comparison with earlier winters

The main features of the “PMP-1 Winters” are summarized and compared with information available on earlier winters, dating back partly till the winter 1951/52. The emphasis is put on a comparison of the stratospheric temperatures over the polar region and of the development of the planetary-scale waves 1 and 2. A possible modulation of these waves by the QBO (Quasi-Biennial Oscillation) and by the sunspot cycle is discussed briefly.     

Interannual variability

The new Reference Atmosphere presented here is based on global satellite data and forms a very useful basis for climatological studies. When using such climatologies it is important to be aware of the well known interannual variability which in the middle atmosphere is particularly large during the northern winters and southern springs.     

Recent work correlating the 11-year solar cycle with atmospheric elements grouped according to the phase of the Quasi-Biennial Oscillation

Atmospheric elements at all levels from the surface to the Middle Atmosphere show a probable association with the 11-year solar cycle in northern winter, which can be observed only if the data are grouped according to the phase of the Quasi-Biennial Oscillation. As the correlations are often of opposite sign in the East and West phase of the QBO, the correlation coefficients are mostly small when one uses as full time series of an atmospheric element. The spatial patterns of the correlations resemble well-known teleconnection patterns. The sparse data and short series on the Southern Hemisphere permit only a limited investigation. Good relationships are found in the antarctic stratosphere in spring and at sea level in winter.Statistical tests suggest that our results did not occur by chance, but since we cannot examine data from before 1952 because we do not know the phase of the QBO before then, and since there is no physical explanation for the large correlation coefficients, we cannot yet exclude the possibility that the results are due to sample variation.Affiliate Scientist at NCAR.Visiting Scientist, Freie Universität Berlin.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Solar Variation and Stratospheric Response

We have shown in several recent publications that it is necessary to group the meteorological data according to the phase of the Quasi-Biennial Oscillation (QBO) throughout the year, in order to find a clear signal of the 11-year sunspot cycle (SSC). This work is summarized here. It is the purpose of this paper (1) to update earlier results of the solar cycle – QBO relationship for the northern winter, (2) to stress the interaction between the hemispheres and (3) to summarize the influence of the QBO on the solar variability signal, as well as the influence of the solar variability signal on the QBO throughout the year. For this, the constructed annual mean of the solar cycle – QBO relationship is introduced.     

THE SIGNAL OF THE 11-YEAR SUNSPOT CYCLE IN THE UPPER TROPOSPHERE-LOWER STRATOSPHERE

The paper summarizes work by the authors over the past ten years on an apparent signal of the 11-year sunspot cycle in the lower stratosphere-upper troposphere. The signal appears as a basic, consistent pattern in correlations between heights of stratospheric constant-pressure levels, at least as high as 25 km, and the solar cycle in which the highest correlations are in the subtropics.The variation of the stratospheric heights in phase with the sunspot cycle are – in the areas of high correlations between the two – associated with temperature variations on the same time scale in the middle and upper troposphere. The spatial distribution of the correlations suggests that the year-to-year changes in tropical and subtropical vertical motions contain a component on the time scale of the solar cycle.In January and February the correlations with the sunspot cycle are smallest. The smallness of the correlations is owing to the fact that they are different in the east and west years of the quasi-biennial oscillation in the equatorial stratospheric winds. The correlation pattern in the east years is the same as in the other seasons and is statistically significant. In the west years the correlations are insignificant outside the arctic, and the positive correlation in the arctic in these years is related to the fact that major midwinter breakdowns of the cyclonic vortex in the west years so far have happened only at maxima in the solar cycle.Until recently reliable continuous series of analyses of the stratosphere were not available for the southern hemisphere. The U.S. National Centers for Environmental Prediction and the National Center for Atmospheric Research have now, however, issued a 23-year series of re-analyzed global data which has made it possible to detect the solar signal on the southern hemisphere. It turns out to be almost the same as that on the northern hemisphere.The correlations between total column ozone and the sunspot cycle are lowest in the equatorial regions, where ozone is produced, and in the subpolar regions, where the largest amounts are found. In the annual mean the largest correlations lie between 5° lat. and 30° lat. We suggest that this distribution of correlations is due to the fact that the subtropical heights of the constant-pressure surfaces in the ozone layer are higher in maximum than in minimum years of the sunspot cycle, and that the higher subtropical heights in the solar maxima depress the poleward transport of ozone through the subtropics and thus create an abundance of ozone.     

The Influence of the 11-year Solar Cycle on the Stratosphere Below 30 km: a Review

The NCEP/NCAR re-analyses of the global data as high as 10hPa have made it possible to examine the influence of the 11-year sunspot cycle on the lower stratosphere over the entire globe. Previously, the signal of the solar cycle had been detected in the temperatures and heights of the stratosphere at 30hPa and below on the Northern Hemisphere by means of a data set from the Freie Universität Berlin. The global re-analyses show that the signal exists on the Southern Hemisphere too, and that it is almost a mirror image of that on the Northern Hemisphere. The largest temperature correlations with the solar cycle move from one summer hemisphere to the other, and the largest height correlations move poleward within each hemisphere from winter to summer.The correlations are weakest over the whole globe in the northern winter. If, however, one divides the data into the winters when the equatorial Quasi-Biennial Oscillation was easterly or westerly, the arctic correlations become positive and large in the west years, but insignificantly small over the rest of the earth. The correlations in the east years are negative in the Arctic but positive in the subtropics and tropics on both hemispheres.The difference between the east and west years in January-February can be ascribed to the fact that the dominant stratospheric teleconnection and the solar influence work in the same direction in the east years but oppose each other in the west years.NCAR is sponsored by the National Science Foundation.