Sørensen (1991) wrongly implemented

As brought to our attention during a review process, the equation for saltation mass flux implemented in SNOWPACK, based on Sørensen (1991), is expressed in the wrong units. See https://doi.org/10.5194/gmd-2022-28-RC1. The coefficients would need to be converted from g/cm/s to kg/m/s.

According to Vionnet, 2012 (https://pastel.archives-ouvertes.fr/tel-00781279v3/document, Fig. 5.3) and Eq. 11 in Vionnet et al. 2014 (https://doi.org/10.5194/tc-8-395-2014), Sørensen (2004) may be a better option for calculating the saltation mass flux.