Comparison of regional climate model and statistical downscaling simulations of different winter precipitation change scenarios over Romania |
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Authors: | A Busuioc F Giorgi X Bi M Ionita |
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Institution: | (1) National Meteorological Administration, Bucharest, Romania;(2) The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy |
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Abstract: | Summary Regional climate model and statistical downscaling procedures are used to generate winter precipitation changes over Romania
for the period 2071–2100 (compared to 1961–1990), under the IPCC A2 and B2 emission scenarios. For this purpose, the ICTP
regional climate model RegCM is nested within the Hadley Centre global atmospheric model HadAM3H. The statistical downscaling
method is based on the use of canonical correlation analysis (CCA) to construct climate change scenarios for winter precipitation
over Romania from two predictors, sea level pressure and specific humidity (either used individually or together). A technique
to select the most skillful model separately for each station is proposed to optimise the statistical downscaling signal.
Climate fields from the A2 and B2 scenario simulations with the HadAM3H and RegCM models are used as input to the statistical
downscaling model. First, the capability of the climate models to reproduce the observed link between winter precipitation
over Romania and atmospheric circulation at the European scale is analysed, showing that the RegCM is more accurate than HadAM3H
in the simulation of Romanian precipitation variability and its connection with large-scale circulations. Both models overestimate
winter precipitation in the eastern regions of Romania due to an overestimation of the intensity and frequency of cyclonic
systems over Europe. Climate changes derived directly from the RegCM and HadAM3H show an increase of precipitation during
the 2071–2100 period compared to 1961–1990, especially over northwest and northeast Romania. Similar climate change patterns
are obtained through the statistical downscaling method when the technique of optimum model selected separately for each station
is used. This adds confidence to the simulated climate change signal over this region. The uncertainty of results is higher
for the eastern and southeastern regions of Romania due to the lower HadAM3H and RegCM performance in simulating winter precipitation
variability there as well as the reduced skill of the statistical downscaling model. |
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