Fig. 1: Clausius–Clapeyron scaling for vapour and frozen moisture at the cold-point tropopause.

The saturation specific humidity at the EFT (Tfrost) calculated via the Clausius–Clapeyron dependency (solid line) describes the mean specific humidity at the cold-point tropopause (\(\bar{q}\), dashed line). The additional frozen moisture can be calculated by considering a constant temperature offset to the EFT.