Developments in the MOSES 2 land-surface model for PILPS 2e

Improved representations of snow processes in vegetation canopies and snow hydrology are implemented in the Met Office Surface Exchange Scheme 2 (MOSES 2) land-surface model. Snow falling on forests is partitioned between interception and throughfall; the intercepted snow is removed by sublimation, melt and unloading. A reduction in sublimation of wind-blown snow through trapping by shrubs is simply represented by reducing the scalar roughness length for shrubs with snow cover. Melt water may be retained and refrozen within snow packs. By reducing the amount of snow lost through sublimation and delaying the runoff of melt water, these modifications are found to improve the simulations of runoff for two Swedish catchments used in the PILPS 2e intercomparison project.