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An improved description of soil hydraulic and thermal properties of arctic peatland for use in a GCM
Author(s) -
Hall Robin L.,
Huntingford Chris,
Harding Richard J.,
Lloyd Colin R.,
Cox Peter M.
Publication year - 2003
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.1265
Subject(s) - peat , environmental science , soil water , soil science , gcm transcription factors , arctic , hydrology (agriculture) , soil horizon , climate change , geology , geotechnical engineering , general circulation model , ecology , oceanography , biology
The UK Meteorological Office Surface Exchange Scheme (MOSES), which is currently implemented within Version 3 of the Hadley Centre GCM, was tested for an arctic peatland site in northern Finland (Kevo). This implementation of MOSES incorporated a new depth‐dependent parameterization of the thermal and hydraulic properties of peat with parameter values derived from measurements reported in the literature. The effect of increasing the number of model soil layers from four to 13 shallower layers was also investigated. Driving data were used that were collected during June, when the peat was still frozen below about 80 mm, to September 1997. Best model performance was given by the 13‐layer, depth‐dependent parameter description for both surface heat fluxes and soil temperatures. The simulated heat fluxes compared well with measurements, but simulated surface temperatures were too high. In preliminary runs the simulated distribution of unfrozen water in the soil was also unrealistic. In particular the model was unable to predict the rapid transition to above‐freezing conditions that occurred throughout the soil profile about the second week in July. Adjusting a parameter ( k ) of the soil‐freezing curve, which for peat can be used as a fitting parameter, produced a big improvement in the soil temperature profiles. A more accurate simulation of the freezing and thawing behaviour of organic soils requires that the processes that are hidden in the modified value of k are explicitly represented. Copyright © 2003 John Wiley & Sons, Ltd.