PMC8429809_01
Walter-Lieth climate diagrams representing the long-term averages (from 1970 to 2016) of monthly air temperature Ta (upper line) and monthly precipitation sum Pr (lower line) at the study sites Furna, Siat (both Upper Rhine Valley), and Sur En (Lower Engadine). The vertical axes for Ta and Pr are scaled with a ratio of 1:2, as after Walter and Lieth (1960-1967) a month is classified as arid if Ta in  C exceeds two times Pr in mm. Black areas indicate periods with Pr > 100 mm, and white areas show periods with Ta < 0 C. Note that the vertical axis is broken at Pr = 100 mm.
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F1
This results from the relatively low amount of Pr in the continental Lower Engadine (Figure 1).