Changes in the Ozone Content over Central Europe During Reversals of Stratospheric Circulation in Late Winter

A superposed epoch analysis during late winter zonal wind reversals was carried out from 18 year observation series (1963 to 1980) of the meridional geopotential height gradient in the 30 mb level (latitude mean) and of the ozone content over central Europe. Experimental data suggest that if planetary waves are responsible for the additional meridional ozone transport during stratospheric warmings, this transport has to take place at heights other than those up to the ozone maximum in the middle latitudes

Spring Changeover of the Middle Atmosphere Circulation Compared with Rocket Wind Data up to 80 Km

The middle atmosphere circulation is governed by two seasonal basic states in winter and summer, twice a year separated by relatively shortlived reversal periods. These seasonal basic states of circulation and the spring changeover period between them are investigated

Solar activity influence on climatic variations of stratosphere and mesosphere in mid-latitudes

The direct modulation of temperature of the mid-latitude mesosphere by the solar-cycle EUV variation, which leads to greater heat input at higher solar activity, is well established. Middle atmosphere temperature modulation by the solar cycle is independently confirmed by the variation of reflection heights of low frequency radio waves in the lower ionosphere, which are regularly monitored over about 30 years. As explained elsewhere in detail, these reflection heights depend on the geometric altitude of a certain isobaric surface (near 80 k), and on the solar ionizing Lyman-alpha radiation flux. Knowing the solar cycle variation of Lyman-alpha how much the measured reflection heights would be lowered with the transition from solar minimum to maximum can be calculated, if the vertical baric structure of the neutral atmosphere would remain unchanged. An discrepancy between expected and observed height change must be explained by an uplifting of the isobaric level from solar minimum to maximum, caused by the temperature rise in the mesosphere. By integrating the solar cycle temperature changes over the height region of the middle atmosphere, and assuming that the lower boundary (tropopause) has no solar cycle variation, the magnitude of this uplifting can be estimated. It is given for the Lidar-derived and for the rocket-measured temperature variations. Comparison suggests that the real amplitude of the solar cycle temperature variation in the mesosphere is underestimated when using the rocket data, but probably overestimated with the Lidar data

Observations of, and sources of the spatial and temporal variability of ozone in the middle atmosphere on climatological time scales (OZMAP) and equatorial dynamics: Seasonal variations of ozone trends

The long term trends (least square linear regression with time) of ozone content at seven European, seven North American, three Japanese and two tropical stations during 21 years (1964 to 1984) are analyzed. In all regions negative trends are observed during the 1970s, but are partly compensated by limited periods of positive trends during the late 1960s and late 1970s. Solely the North American ozone data show negative trends in all 10 year periods. When the long term ozone trends are evaluated for each month of the year separately, a seasonal variation is revealed, which in Europe and North America has largest negative trends in late winter and spring. While in Europe the negative trends in winter/spring are partly compensated by positive trends in summer, in North America the summer values reach only zero, retaining the significant negative trend in annual mean values. In contrast to the antarctic ozone hole, the spring reduction of ozone in Europe and in North America is associated with stratospheric temperatures increasing in the analyzed period and therefore is consistent with the major natural ozone production and loss processes

Very low zonally asymmetric ozone values in March 1997 above the North Atlantic-European region, induced by dynamic processes

International audienceThe total ozone distribution in March 1997 showed very low values in the North Atlantic-European region, even lower than in the years before. A spatial pattern correlation between the zonally asymmetric part of total ozone and that of the 300 hPa surface geopotential of the Northern Hemisphere was applied to examine the spatial structure of the low ozone values and its dynamic dependence. A trend analysis in the North Atlantic-European region was carried out to determine to what extent the low March 1997 ozone values are related to the decadal change of meteorological parameters in the lower stratosphere, observed since the 1980s, in comparison to the interannual variability. The conclusion is that the very low ozone values above the North Atlantic-European region in March 1997 were mainly induced by dynamic processes, namely their decadal change as well as their interannual variability

Longitude-dependent decadal ozone changes and ozone trends in boreal winter months during 1960-2000

This study examines the longitude-dependent decadal changes and trends of ozone for the boreal winter months during the period of 1960–2000. These changes are caused primarily by changes in the planetary wave structure in the upper troposphere and lower stratosphere. The decadal changes and trends over 4 decades of geopotential perturbations, defined as a deviation from the zonal mean, are estimated by linear regression with time. The decadal changes in longitude-dependent ozone were calculated with a simple transport model of ozone based on the known planetary wave structure changes and prescribed zonal mean ozone gradients. For December of the 1960s and 1980s a statistically significant Rossby wave track appeared over the North Atlantic and Europe with an anticyclonic disturbance over the Eastern North Atlantic and Western Europe, flanked by cyclonic disturbances. In the 1970s and 1990s statistically significant cyclonic disturbances appeared over the Eastern North Atlantic and Europe, surrounded by anticyclonic anomalies over Northern Africa, Central Asia and Greenland. Similar patterns have been found for January. The Rossby wave track over the North Atlantic and Europe is stronger in the 1980s than in the 1960s. For February, the variability of the regression patterns is higher. For January we found a strong alteration in the modelled decadal changes in total ozone over Central and Northern Europe, showing a decrease of about 15 DU in the 1960s and 1980s and an increase of about 10 DU in the 1970s and 1990s. Over Central Europe the positive geopotential height trend (increase of 2.3 m/yr) over 40 years is of the same order (about 100 m) as the increase in the 1980s alone. This is important to recognize because it implies a total ozone decrease over Europe of the order of 14 DU for the 1960–2000 period, for January, if we use the standard change regression relation that about a 10-m geopotential height increase at 300 hPa is related to about a 1.4-DU total ozone decrease

Denn sie tun nicht, was sie wissen

Die Diskrepanz zwischen ökologischem Bewusstsein und Verhalten ist hinlänglich bekannt. Empirische Befunde belegen nun, dass Individuen ihr eigenes, nichtökologisches Handeln in Einklang bringen mit ihrem Anspruch, ökologisch zu denken. Insofern kann diese Kluft vielmehr als Problem der Wahrnehmung verstanden werden

Solar 27-day signatures in standard phase height measurements above central Europe

We report on the effect of solar variability at the 27-day and the 11-year timescales on standard phase heightmeasurements in the ionospheric D region carried out in cen-tral Europe. Standard phase height corresponds to the re-flection height of radio waves (for constant solar zenith dis-tance) in the ionosphere near 80 km altitude, where NO isionized by solar Lyman-αradiation. Using the superposedepoch analysis (SEA) method, we extract statistically highlysignificant solar 27-day signatures in standard phase heights.The 27-day signatures are roughly inversely correlated to so-lar proxies, such as the F10.7 cm radio flux or the Lyman-αflux. The sensitivity of standard phase height change to so-lar forcing at the 27-day timescale is found to be in goodagreement with the sensitivity for the 11-year solar cycle,suggesting similar underlying mechanisms. The amplitude ofthe 27-day signature in standard phase height is larger duringsolar minimum than during solar maximum, indicating thatthe signature is not only driven by photoionization of NO. Weidentified statistical evidence for an influence of ultra-longplanetary waves on the quasi 27-day signature of standardphase height in winters of solar minimum periods

Evidence of CO2-induced progressive cooling of the middle atmosphere derived from radio observations

Reflection heights of low frequency radio waves in midlatitude summer, which are closely associated with the neutral atmosphere isobaric level of 0.0052 hPa, exhibit a statistically significant downgoing trend from 1962 to 1987. This indicates a systematic decrease of air pressure at 80 km height by 10.3 plus or minus 4.9 percent over this period, to be regarded as a sufficient evidence of a true signal of progressive cooling of the middle atmosphere, expected with the growing content of CO2 and other greenhouse bases in the atmosphere. It is quantitatively consistent with a temperature decrease at the stratopause by about 4 K, as predicted by the recent model of interactive greenhouse and ozone processes of Brasseur and de Rudder (1987)