Validation of present-day regional climate simulations over Europe: LAM simulations with observed boundary conditions |
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Authors: | J H Christensen B Machenhauer R G Jones C Schär P M Ruti M Castro G Visconti |
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Institution: | Danish Meteorological Institute, Copenhagen ?, Denmark, DK University of L’Aquila, Coppito, Italy, IT
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Abstract: | Nested limited-area modelling is one method of down-scaling general circulation model (GCM) climate change simulations. To
give credibility to this method the nested limited-area model (LAM) must be shown to simulate local present-day climate conditions
fairly accurately. Here seven different European limited-area models driven by observed boundary conditions (operational weather
forecast analyses) are validated against observations, and inter-compared for summer and winter months. Relatively large biases
are found. In summer large positive surface air temperature biases are found over southeast Europe. The main reason is deficiencies
in the surface hydrological schemes causing an unrealistic drying of the soil. In at least one of the models, most likely
several of them, an additional factor is an overestimation of incoming solar radiation. Apart from excessive precipitation
in mountainous areas in some models they generally show a negative bias due to the drying and decreased advection from the
Atlantic. In winter most models have a positive precipitation bias which seems to be caused by an enhancement of advection
from the Atlantic and enhanced cyclone activity. Surface air temperature biases are negative probably due to an underestimation
of the incoming longwave radiation.
Received: 11 December 1996 / Accepted: 17 March 1997 |
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