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COUP

Purpose

To quantify and increase the understanding concerning basic hydrological and biological processes in the soil-plant-atmosphere system.

Brief Description

A review of model development and use was provided by Jansson (2012).

The model simulates soil water and heat processes in many type of soils; bare soils or soils covered by vegetation. The basic structure of the model is a depth profile of the soil. Processes such as snow-melt, interception of precipitation and evapotranspiration are examples of important interfaces between soil and atmosphere. Two coupled differential equations for water and heat flow represent the central part of the model. These equations are solved with an explicit numerical method. The basic assumptions behind these equations are very simple:

1. The law of conservation of mass and energy and
2. flows occur as a result of gradients in water potential (Darcy's Law) or temperature (Fourier's law).

The calculations of water and heat flows are based on soil properties such as: the water retention curve, functions for unsaturated and saturated hydraulic conductivity, the heat capacity including the latent heat at thawing/melting and functions for the thermal conductivity. The most important plant properties are: development of vertical root distributions, the surface resistance for water flow between plant and atmosphere during periods with a non limiting water storage in the soil, how the plants regulate water uptake from the soil and transpiration when stress occurs, how the plant cover influences both aerodynamic conditions in the atmosphere and the radiation balance at the soil surface.

All of the soil-plant-atmosphere system properties are represented as parameter values. Meteorological data are driving variables to the model. Most important of those are precipitation and air temperature but also air humidity, wind speed and cloudiness are of great interest. Results of a simulation are such as: temperature, content of ice, content of unfrozen water, water potential, vertical and horizontal flows of heat and water, water uptake by roots, storages of water and heat, snow depth, water equivalent of snow, frost depth, surface runoff, drainage flow and deep percolation to ground water.

In addition to the water and heat conditions also the plant dynamics and related turnover of nitrogen and carbon may be simulated. The abiotic and biotic processes may be linked in different ways also to handle the feedback between the physical driving forces and the plant development.

Detailed description

Documentation and manual are available on the model's homepage.

References

• Wu SH, Jansson P-E, Kolari P (2012). The role of air and soil temperature in the seasonality of photosynthesis and transpiration in a boreal Scots pine ecosystem Agricultural and Forest Meteorology 156: 85–103 doi:10.1016/j.agrformet.2012.01.006.
• Jansson, P-E (2012). CoupModel: Model Use, Calibration, and Validation Transcactions of the ASABE 55(4): 1337-1346.
• Wu SH, Jansson P-E, Kolari P (2011). Modelling seasonal course of carbon fluxes and evapotranspiration in response to low temperature and moisture in a boreal Scots pine ecosystem Ecological Modelling 222(17): 3103-3119 doi:10.1016/j.ecolmodel.2013.03.015.
• Hollesen J, Elberling B and Jansson PE (2011). Future active layer dynamics and carbon dioxide production from thawing permafrost layers in Northeast Greenland Global Change Biology 17(2): 911–926 doi:10.1111/j.1365-2486.2010.02256.x.
• Norman J, Jansson P-E, Farahbakhshazad N, Butterbach-Bahl K, Li C, Klemedtsson L (2008). Simulation of NO and N₂O emissions from a spruce forest during a freeze/thaw event using an N-flux submodel from the PnET-N-DNDC model integrated to CoupModel Ecological Modelling 216(1): 18–30 doi:10.1016/j.ecolmodel.2008.04.012.
• Jansson P-E, Svensson M, Kleja DB, Gustafsson, D (2008). Simulated climate change impacts on fluxes of carbon in Norway spruce ecosystems along a climatic transect in Sweden Biogeochemistry 89(1): 89–94 doi:10.1007/s10533-007-9147-6.
• Svensson M, Jansson P-E, Berggren Kleja D (2007). Modelling soil C sequestration in spruce forest ecosystems along a Swedish transect based on current conditions Biogeochemistry 89(1): 95-119 doi:10.1007/s10533-007-9134-y.
• Gustafsson, David, Elisabet Lewan and Per-Erik Jansson (2004). Modelling water and heat balance of boreal landscape, comparison of forest and arable land in Scandinavia Journal of Applied Meteorology 43, 1750-1767 doi:10.1175/JAM2163.1.