Bottom Same but as accounted for by multiple linear regression Eq 1 Fig WP1 3

Bottom same but as accounted for by multiple linear

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Bottom: Same, but as accounted for by multiple linear regression (Eq. 1). Fig. WP1-3: Linear trend term, in percent per 10 years, as derived by the regression and as a function of season and altitude. White areas in this Figure (and the following ones) represent regions where the predictor is not contributing significantly ( at the 90% level) to ozone variance.
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However, it must be stated that the tropospheric ozone increase has more or less stopped in the 1990s and a linear trend is not a good predictor for tropospheric ozone changes anymore. Instead, a proxy for tropospheric precursor emissions (NO y and/or Volatile Organic Compounds) should be used in Eq. 1 in the future. A notable feature of Figure WP1-3 is, that this increase seems to reach into the lowermost stratosphere in fall (SON). A very similar feature is found in the ECHAM4.L39(DLR)/CHEM simulations (compare Fig. WP1-10). The linear trend term is generally not significant throughout the lowermost stratosphere (10 km to 17 km). There, meteorological predictors, i.e. tropospheric circulation patterns, are the main contributors to ozone variance. Figure WP1-4 shows these large ozone fluctuations, 10 to 40%, that are strongest in winter right above the tropopause. Above about 20 km the meteorological influence disappears. A notable exception is the region between 25 km and 45 km in winter. There we most likely see a manifestation of well known stratospheric/tropospheric coupled circulation-modes, e.g. the Arctic Oscillation. Fig. WP1-4: Ozone fluctuations (2σ) accounted for by tropospheric meteorological predictors. Fluctuations are given in percent of the climatological mean for each season and altitude. Figure WP1-5 plots the ozone fluctuations attributed to the QBO. Here we can see four regimes. Two of them show a clear downward propagation of the QBO-signal. For example, a QBO signal appears around 45 km altitude in summer (JJA), propagating down to 30 km until spring (MAM, ≈ -1.7 km/month). A second downward propagation can be seen from about 20 km in winter (DJF) to 16 km in summer (≈ -0.7 km/month). For comparison, the QBO itself propagates down by typically 1 to 1.5 km/month. In between these two regimes, there is an altitude region (28 to 32 km) where a QBO-signal is present throughout the year at constant altitude. The strongest QBO signal, with ozone fluctuations exceeding 14% (2σ), is found in spring near the tropopause. 7
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Fig. WP1-5: Ozone fluctuations (2σ) attributed to the QBO. Fluctuations are given in percent of the climatological mean for each season and altitude. Fig. WP1-6: Same as Figures WP1-4 and WP1-5, but for the 11-year solar cycle. The 11-year solar cycle is a significant contributor mostly in the 20 to 27 km altitude range, with ozone fluctuations between 2 and 4% (Figure WP1-6). The lidar data, above 30 km, show a significant solar cycle effect only in summer around 33 km. In part this lack of signal above 30 km may be due to the fact that 14 years of lidar measurements are too short to derive solar cycle and trend components. The sonde time series below 30 km is much longer, 34 years. The isolated peak in spring at 15 km may well be erroneous (90% significance = 10% probability of error).
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