A catchment‐based approach to modeling land surface processes in a general circulation model: 1. Model structure

Abstract

Abstract. A new strategy for modeling the land surface component of the climate system is described. The strategy is motivated by an arguable deficiency in most state-of-the-art land surface models, namely, the disproportionately higher emphasis given to the formulation of one-dimensional, vertical physics relative to the treatment of horizontal heterogeneity in surface properties, particularly subgrid soil moisture variability and its effects on runoff generation. The new strategy calls for the partitioning of the continental surface into a mosaic of hydrologic catchments, delineated through analysis of high-resolution surface elevation data. The effective "grid" used for the land surface is therefore not specified by the overlying atmospheric grid. Within each catchment, the variability of soil moisture is related to characteristics of the topography and to three bulk soil moisture variables through a well-established model of catchment processes. This modeled variability allows the partitioning of the catchment into several areas representing distinct hydrological regimes, wherein distinct (regime specific) evaporation and runoff parameterizations are applied. Care is taken to ensure that the deficiencies of the catchment model in regions of little to moderate topography are minimized.

Introducing Hysteresis in Snow Depletion Curves to Improve the Water Budget of a Land Surface Model in an Alpine Catchment

“…The multilayer, physically based snow scheme included in the CLSM (Lynch-Stieglitz 1994)i so fi n t e r m e d i a t e complexity according to Boone and Etchevers's (2001) classification of snow schemes and has shown good performance in different studies (Stieglitz et al 2001;Gascoin et al 2009b;Koster et al 2010). The snow model vertically discretizes the snowpack into three layers, and each of them is characterized by its heat content, SWE, and snow depth (Lynch-Stieglitz 1994;Stieglitz et al 2001;D ery et al 2004).…”

“…The Catchment land surface model (CLSM) is an LSM developed by Koster et al (2000) and Ducharne et al (2000) to generate water and energy fluxes between land surfaces and the atmosphere in general circulation models (GCMs) in which a multilayer, physically based snow scheme is included (Lynch-Stieglitz 1994). We applied this model in the Durance watershed (approximately 14 000 km 2 ) located in the southern French Alps with an altitude range of 4000 m (see Fig.…”

Upper Blue Nile basin water budget from a multi-model perspective

“…In contrast to the traditional gridded delineation, CLSM divides areas into irregularly shaped topographic catchments, which each contain a saturated fraction, a sub-saturated fraction, and a wilting fraction. These fractions evolve over time, and are used to determine fluxes and soil states within the catchment [more details can be found in Koster et al, 2000;Reichle et al, 2011;Houborg et al, 2012]. The soil profile depths were compiled from the FAO/ UNESCO Soil Map of the World (Webb et al, 1991).…”

Comparing potential recharge estimates from three Land Surface Models across the western US

“…Several Land Surface Models (LSMs) (e.g. SAC-SMA (Burnash et al, 1973;Burnash, 1995;SSiB, Xue et al, 1991); Mosaic (Koster and Suarez, 1996); NSSIP (Koster et al, 2000); Variable Infiltration Capacity (VIC; Liang et al, 1994); Noah (Ek et al, 2003;Niu et al, 2011); and CLM (Bonan et al, 2012(Bonan et al, , 2011) have been developed over the last few decades to better represent land surface and atmospheric processes as well as improve estimates of various water, energy and carbon fluxes at the land surface. These models could be a valuable tool for estimating current and future recharge estimates due to projected climate change.…”