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Assessing the Skill of Precipitation and Temperature Seasonal Forecasts in Spain. Windows of Opportunity Related to ENSO Events.

Journal: Journal of Climate
Year: 2010   Volume: 23
Initial page: 209   Last page: 220
Status: Published
In this status since: 12 Jan 2010
PDF file: 2010_frias_JC.pdf
DOI: 10.1175/2009JCLI2824.1

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The skill of state-of-the-art operational seasonal forecast models in extra-tropical latitudes is assessed using a multimodel ensemble from the DEMETER project. In particular, we analyze probabilistic forecasts of surface precipitation and maximum temperature in Spain using a high resolution observation gridded dataset (Spain02). To this aim, we use a simple statistical test based on the observed and predicted tercile anomalies. First, we consider the whole period 1960-2000 and show that the only significant skill is found for dry events in autumn. Then, we study the influence of ENSO events as a potential source of conditional predictability and restrict the validation to strong La Niña or El Niño periods. Skillful seasonal predictions are found in partial agreement with the observed teleconnections derived from the historical records. On the one hand, predictability is found in spring related to El Niño events for dry events over the south and the Mediterranean coast and for hot events in the south-east areas. On the other hand, La Niña drives predictability in winter for dry events over the western part and for hot events in summer over the south and the Mediterranean coast.

In this study we consider both the direct model outputs and the post processed predictions obtained using a statistical downscaling method based on analogs. In general, the use of the downscaling method outperforms the direct output for precipitation, whereas in the case of the temperature no improvement is obtained.