Version 3.0 of the Crocus snowpack model

Abstract. This article presents a comprehensive description of the 3.0 stable release of the Crocus snowpack model in the SURFEX modelling platform. It synthesizes and harmonizes a number of equations disseminated in various previous publications, introduces a number of unpublished parameterizations and includes new developments implemented since 2012. Among the novelties, an explicit representation of the evolution of impurity mass in snow (e.g. black carbon, mineral dust) allows representing their impact on solar radiation absorption in the snowpack at different wavelengths and their feedback on all snowpack properties. The model also allows the formation of surface ice layers due to freezing rain. In addition, Crocus is coupled to the MEB "big-leaf" vegetation scheme and can therefore be applied in forested areas. A module for snow management can also be optionally activated to simulate the snowpack on ski slopes in ski resorts. The model can be coupled with various blowing snow schemes. The MEPRA expert system which analyses the mechanical stability of the simulated snowpack has been implemented directly within SURFEX. A multiphysics version of the model (ESCROC) was also developed by implementing from 2 to 4 parameterizations from the literature for each physical process represented by empirical parameterizations. The different combinations allow the quantification of simulations uncertainty for various applications. Finally, a technical solution was proposed for externalized applications allowing the use of the scheme in other Land Surface Models. The paper also reviews the available scientific evaluations and applications of the model. It describes its numerical efficiency and the main scientific and technical challenges providing guidance for the future of snow modelling.