Comparing COSMO-CLM simulations and MODIS data of snow cover extent and distribution over Italian Alps
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- Da Ronco, P., De Michele, C., Montesarchio, M. et al. Clim Dyn (2016) 47: 3955. doi:10.1007/s00382-016-3054-2
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Snow cover maps from Earth Observation (EO) satellites are valuable datasets containing large-scale information on snow cover extent, snow cover distribution and snow cover duration. In evaluating the performances of Regional Climate Models, EO data can be a valid piece of information alternative to in-situ measurements, which require a dense network of stations covering the entire altitudinal range and techniques for interpolating the values. In this context, MODIS snow products play a leading role providing several types of snow cover maps with high spatial and temporal resolutions. Here, we assess snow cover outputs of a high resolution Regional Climate Model (RCM) using MODIS maps of snow covered area over the Po river basin, northern Italy. The dataset consists of 9 years of MODIS data (2003–2011) cleaned from cloud cover by means of a cloud removal procedure. The maps have 500 m spatial resolution and daily temporal resolution. The RCM considered is COSMO-CLM, run at 0.0715° resolution (about 8 km) and coupled with the soil module TERRA_ML. The ERA-Interim reanalyses are used as initial and boundary conditions. The results show a good agreement between observed and simulated snow cover duration and extension. COSMO-CLM is able to reproduce the inter-annual variabilities of snow cover features as well as the seasonal trend of snow cover duration and extension. Limitations emerge when the RCM simulates the progressive depletion of the snow cover in spring. Simulated snowmelt occurs faster than the observed one. Then, we investigate the influence of the spatial resolution of the climate model. The simulation at 0.0715° (about 8 km) is compared to a simulation performed at 0.125° (about 14 km). The comparison highlights the benefits provided by the higher spatial resolution in the accumulation season, reflecting the improvements obtained in temperature and precipitation fields.