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A similar, but not identical, comparison for the transition from 1988 to 1989 in ERA-Interim (Fig. 2) reveals that in the troposphere and stratosphere (from 1000 hPa to about 1 hPa), the differences have, if anything, a slightly larger magnitude than those in the 2009/2010 ERA5 transition, and ERA-Interim exhibits transition differences lower down in the atmosphere. However, in the lower to mid-mesosphere (from about 1 hPa to 0.1 hPa, with the latter being the top of the ERA-Interim domain), the differences in the ERA-Interim transition are generally smaller than in the ERA5 transition, having magnitudes less than 2 K. The spread in temperature, for September - November 2009, in the ERA5 EDA 10 member ensemble (Fig. 3), which gives some indication of the uncertainty, is generally larger than the ERA5 transition differences in the lower latitudes of the troposphere and stratosphere, particularly at lower latitudes. The largest values of the spread are located in the mid to upper stratosphere, at lower latitudes, where values exceed 0.8 K. This region merges into a second area of relatively large uncertainty, in the northern mid-latitudes of the mid-mesosphere, where values exceed 0.7 K. In general, the spread in the mesosphere is smaller than the ERA5 transition differences.
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