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Fig9.1.4.9-3: Illustration of temperature observations which are accepted for use in analysis of T2m by 4D-Var.  Temperatures are adjusted by 5 K/km from station height up or down to the model orography height.  Temperatures at stations >200m higher or >400m lower than model contour orography height are not used.  Stations on mountain tops and in deep valleys are thus excluded while retaining the majority of observations, including those in shallow valleys where many stations are located.

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