Abstract
Abstract. GEOtop is a fine-scale grid-based simulator that represents the heat and water budgets at and below the soil surface. It describes the three-dimensional water flow in the soil and the energy exchange with the atmosphere, considering the radiative and turbulent fluxes. Furthermore, it reproduces the highly non-linear interactions between the water and energy balance during soil freezing and thawing, and simulates the temporal evolution of the water and energy budgets in the snow cover and their effect on soil temperature. Here, we present the core components of GEOtop 2.0 and demonstrate its functioning. Based on a synthetic simulation, we show that the interaction of processes represented in GEOtop 2.0 can result in phenomena that are significant and relevant for applications involving permafrost and seasonally frozen soils, both in high altitude and latitude regions.
Highlights
Frozen soil and snow cover interact in various ways with hydrology, climate, ecosystems and with human infrastructures
– Diffuse radiation is calculated as two components: (i) one coming from the atmosphere calculated multiplying the hemispheric diffuse radiation by the sky view factor (Vf), which is a topographical parameter that accounts for the portion of the sky that is seen from a pixel and varies from 0 to 1; and (ii) a second component resulting from the shortwave radiation reflected from the terrain seen from the pixel
The water flow is calculated in an uncoupled way in the following steps: (i) the heat Eq (1) for the snow cover is solved assuming that the liquid water does not move, obtaining a “static” solution; (ii) the incoming water flow from above is added; (iii) the internal energy content of the inflowing water is added to the internal energy of the snow, assuming that there is an instantaneous energy mixing that may lead to the partial or complete refreezing of the liquid water; (iv) the outgoing downward water flux is calculated with the new state variables
Summary
Frozen soil and snow cover interact in various ways with hydrology, climate, ecosystems and with human infrastructures. As a novel combination of processes represented, this paper presents GEOtop 2.0, an improved version of the opensource software GEOtop, which simulates the energy and water balance at and below the land surface, soil freezing, snow cover dynamics, and terrain effects. GEOtop describes the evolution in time of temperature and water content in the soil and snow cover and is driven by meteorological forcings This is accomplished by solving the heat and water flow equations with boundary conditions accounting for the interactions with the atmosphere at the surface in terms of energy and water fluxes. A simulation experiment is presented in order to demonstrate that the combination of terrain effects, energy and water balance produce unique results for different meteorological forcings, making an a priori exclusion of any of these processes difficult and providing one important rationale for developing and using a simulator such as GEOtop
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