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The ERA5 transition differences for specific humidity (Fig. 7) are generally small apart from below 5 %, apart from at low latitudes in the mesosphere , particularly at low latitudes above 0.05 hPa, where differences exceed 10 %.
In summary, the ERA5 transition in 2009/2010 exhibits small differences in the troposphere, but the mesosphere is problematic. There, the differences exceed those in ERA-Interim and are much larger than the ensemble spread.
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