The GEOTOP snow module

2000

Here a snow accumulation and melt module implemented in the GEOTOP model is presented and tested. GEOTOP is a distributed model of the hydrological cycle, based on digital elevation models (DEMs), which calculates the discharge at the basin outlet and estimates the local and distributed values of several hydro-meteorological quantities. It solves the energy and the mass balance jointly and

GEOtop is a small-scale grid-based simulator that represents the heat and water budgets at and below the soil surface. It represents the energy exchange with the atmosphere, considering the radiative and turbulent fluxes, and describes the three-dimensional subsurface water flow. Furthermore, it reproduces the highly non-linear interaction of the water and energy balance during soil freezing and thawing, and describes the temporal evolution of water and energy budgets in the snow cover and their effect on soil temperature.

Hydrological Processes, 1999

Snowmelt is the principal source for soil moisture, groundwater recharge , and stream-¯ow in mountainous regions of the western US, Canada, and other similar regions of the world. Information on the timing, magnitude, and contributing area of melt under variable or changing climate conditions is required for successful water and resource management. A coupled energy and mass-balance model ISNOBAL is used to simulate the development and melting of the seasonal snowcover in several mountain basins in California, Idaho, and Utah. Simulations are done over basins varying from 1 to 2500 km 2 , with simulation periods varying from a few days for the smallest basin, Emerald Lake watershed in California, to multiple snow seasons for the Park City area in Utah. The model is driven by topographically corrected estimates of radiation, temperature, humidity, wind, and precipitation. Simulation results in all basins closely match independently measured snow water equivalent, snow depth, or runo during both the development and depletion of the snowcover. Spatially distributed estimates of snow deposition and melt allow us to better understand the interaction between topographic structure, climate, and moisture availability in mountain basins of the western US. Application of topographically distributed models such as this will lead to improved water resource and watershed management.

Modeling snowmelt is important for water resources management and the assessment of spring snowmelt flood risk. The objective of this study was to develop a physically based module for the WetSpa model to improve the simulation of snowmelt processes. The improved model is applied, calibrated, and verified on the Hornad watershed, upstream of Margecany, Western Carpathians, Slovakia, with 10 years of observed daily precipitation and air temperature, and estimated daily potential evaporation. Daily discharge data of the gauging station at Margecany is used for model calibration and verification. The model proves to predict accurately snow accumulation and snowmelt floods, although the parameters of the snow simulation module are preset and not adjusted by model calibration. In order to show the performance of the model, two particular snow accumulation and melt periods are discussed in detail. The relevant terms of the snowpack mass and energy balances as well as the related heat and mass transport processes are discussed. The study demonstrates that accurate snowmelt prediction based on a physically energy budget approach is possible with controlling parameters that do not need any calibration.

1994

This paper describes an energy balance snowmelt model developed for the prediction of rapid snowmelt rates responsible for soil erosion and water input to a distributed water balance model. The model uses a lumped representation of the snowpack with two primary state variables, namely, water equivalence and energy content relative to a reference state of water in the ice phase at 0 o C. This energy content is used to determine snowpack average temperature or liquid fraction. This representation of the snowpack is used in a distributed version of the model with each of these state variables modeled at each point on a rectangular grid corresponding to a digital elevation model. Inputs are air temperature, precipitation, wind speed, humidity and radiation at hourly time steps. The model uses physically-based calculations of radiative, sensible, latent and advective heat exchanges. An equilibrium parameterization of snow surface temperature accounts for differences between snow surface temperature and average snowpack temperature without having to introduce additional state variables. Melt outflow is a function of the liquid fraction, using Darcy's law. This allows the model to account for continued outflow even when the energy balance is negative. A detailed description of the model is given together with results of tests against data collected at the Central Sierra Snow Laboratory, California; Reynolds Creek Experimental Watershed, Boise Idaho; and at the Utah State University drainage and evapotranspiration research farm, Logan Utah. The testing includes comparisons against melt outflow collected in melt lysimeters, surface snow temperatures collected using infrared temperature sensors and depth and water equivalence measured using snow core samplers.

Journal of Geophysical Research: Atmospheres, 2015

Energy budget-based distributed modeling of snow and glacier melt runoff is essential in a hydrologic model to accurately describe hydrologic processes in cold regions and high-altitude catchments. We developed herein an integrated modeling system with an energy budget-based multilayer scheme for clean glaciers, a single-layer scheme for debris-covered glaciers, and multilayer scheme for seasonal snow over glacier, soil, and forest within a distributed biosphere hydrological modeling framework. Model capability is demonstrated for Hunza River Basin (13,733 km 2) in the Karakoram region of Pakistan on a 500 m grid for 3 hydrologic years (2002-2004). Discharge simulation results show good agreement with observations (Nash-Sutcliffe efficiency = 0.93). Flow composition analysis reveals that the runoff regime is strongly controlled by the snow and glacier melt runoff (50% snowmelt and 33% glacier melt). Pixel-by-pixel evaluation of the simulated spatial distribution of snow-covered area against Moderate Resolution Imaging Spectroradiometer-derived 8 day maximum snow cover extent data indicates that the areal extent of snow cover is reproduced well, with average accuracy 84% and average absolute bias 7%. The 3 year mean value of net mass balance (NMB) was estimated at +0.04 myr À1. It is interesting that individual glaciers show similar characteristics of NMB over 3 years, suggesting that both topography and glacier hypsometry play key roles in glacier mass balance. This study provides a basis for potential application of such an integrated model to the entire Hindu-Kush-Karakoram-Himalaya region toward simulating snow and glacier hydrologic processes within a water and energy balance-based, distributed hydrological modeling framework.

This paper presents an attempt at deterministically modeling spatially distributed snowmelt in an alpine cfitchment. The basin is 9.4 km 2 in area and elevations range from 1900 to 3050 m above sea level. The model makes use of digital terrain data with 25 m grid spacing. Energy balance components are calculated for ea6h grid element taking topographic. variations of solar radiation into account. For each grid element albedo and snow surface temperatures are simulated. Model performance is evaluated on the basis of snow cover depletion patterns as derived from weekly air photographs. The use of spatially distributed data allows for addressing individual model components. Results indicate that the basic model assumptions are realistic. Model inadequacies are shown to arise from processes not included in the model such as avalanching and long wave emission fxom surrounding terrain as well as inaccurate model parameters. Numerous papers have been published on distributed model components su:Ch as radiation [e.g., Dozier, 1980; Olyphant, 1986] and some papers on the distribution of water equivalent [Woo et al? 1983a; Elder et al., 1989]. However, no more than a few studies deal with spatially distributed sn0wmelt models. Charbonneau et al. [1981] presented a model which accounted for variations in shortwave radiation and snow surface temperature at slopes of different aspect.

Journal of Hydrologic Engineering, 2004

A simple snowdrift model was developed, incorporated into a distributed winter-time hydrological model, and tested against snow measurements from a hillside in eastern Washington State. Snow movement can be an important factor in the distribution of spring soil moisture and runoff. Although current hydrological models often attempt to account for heterogeneities in precipitation distribution, they do not account for snowdrift. Snow melts and accumulates during the same times that it is redistributed. Therefore, evaluation required a snowmelt/accumulation model to be coupled with the snowdrift model. The snowmelt/accumulation model used the standard energy balance approach and performed well, i.e., standard errors of snow water equivalent Ϸ1 cm. The snowdrift model's simulated snow distribution generally agreed with observed snow distribution across a hill. Most notable were the model's ability to correctly place a snowdrift on the lee side of the hill and its ability to predict snow removal from nondrift areas. The effects of snow redistribution and the model's ability to reproduce these were obvious when overlaid on model results that ignored snowdrift.

Geoscientific Model Development Discussions

Enhanced temperature-index distributed models for snowpack simulation, incorporating air temperature and a term for clear sky potential solar radiation, are increasingly used to simulate the spatial variability of the snow water equivalent. This paper presents a new snowpack model (termed TOPMELT) which integrates an enhanced temperature index model into a lumped basin scale hydrological model by exploiting a statistical representation of the distribution of clear sky potential solar radiation. This is obtained by discretising the full spatial distribution of clear sky potential solar radiation into a number of radiation classes. The computation required to generate a spatially distributed water equivalent reduces to a single calculation for each radiation class. This turn into a potentially significant advantage when parameter sensitivity and uncertainty estimation procedures are carried out. The model includes a routine, which accounts for the variability of clear sky radiation distributions with time, ensuring a consistent temporal simulation of the snow mass balance. Thus, the model resembles a classical temperature-index model when only one radiation class for each elevation band is used, whereas it approximates a fully distributed model with increasing the number of the radiation classes (and correspondingly decreasing the area corresponding to each class). TOPMELT is applied over the Aurino basin at S. Giorgio, a 614 km 2 catchment in the Upper Adige river basin (Eastern Alps, Italy) to examine the sensitivity of the snowpack model results to the temporal and spatial aggregation of the radiation fluxes.

Journal of Hydrometeorology, 2006

SnowModel is a spatially distributed snow-evolution modeling system designed for application in landscapes, climates, and conditions where snow occurs. It is an aggregation of four submodels: MicroMet defines meteorological forcing conditions, EnBal calculates surface energy exchanges, SnowPack simulates snow depth and water-equivalent evolution, and SnowTran-3D accounts for snow redistribution by wind. Since each of these submodels was originally developed and tested for nonforested conditions, details describing modifications made to the submodels for forested areas are provided. SnowModel was created to run on grid increments of 1 to 200 m and temporal increments of 10 min to 1 day. It can also be applied using much larger grid increments, if the inherent loss in high-resolution (subgrid) information is acceptable. Simulated processes include snow accumulation; blowing-snow redistribution and sublimation; forest canopy interception, unloading, and sublimation; snow-density evolut...