This module corrects the air temperature for the effect of the katabatic flows on the glaciated pixels. The flows are computed automatically for each glaciated pixel following (Quinn, 1991) (see below). Then the air temperature correction is computed according to (Greuell and Bohm, 1998) with the improvements by (Ayala, Pellicciotti and Shea, 2015) (see Glaciers::correctTemperatures). This model is enabled by setting to TRUE the GLACIER_KATABATIC_FLOW key in the [ALPINE3D] section.

Then, two calibration parameters must be set:

KATABATIC_LAYER_HEIGHT which represents the katabatic layer height in meters. It was around 17m in the original paper and around 5m in (Ayala et al.);
KATABATIC_K_COEFFICIENT which takes into account the lateral energy fluxes on the glacier tongue in (Ayala et al.). This was around 7°C but can be set to 0 (default value) to use a pure (Greuell and Bohm, 1998) model.
KATABATIC_SCALING might also be provided. This factor reduces the katabatic flow reach. A value of .25 seems to work quite well

multiple_flow

The computation of the katabatic flows paths is based on the multiple flow direction algorithm and associates to each cell an upslope area that is based on the number of cells that flow into it. This follows "The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models", Quinn P., Chevallier P., Planchon O., hydrological processes, 5, 1991, pp 59-79.

Remarks: This code is still experimental and awaits proper validation!!