Maria Jesus Casado, Maria Asuncion Pastor
AEMET
C/ Leonardo Prieto Castro 8, 28040 Madrid, Spain
Francisco J. Doblas-Reyes
ECMWF, Shinfield Park
RG2 9AX, Reading, UK
This paper illustrates the ability of a set of different atmospheric circulation
classifications from the COST733 Action "Harmonisation and Applications of Weather
Types Classifications for European Regions" to describe the variability of winter
precipitation over different climatic regions of Spain for the period 1961-1990. A
Principal Component Analysis was first applied to identify the three regions
(Atlantic, Mediterranean and Northern) with similar precipitation climatology.
Different metrics such as the explained variation (EV), Pseudo-F index (PF) and the
standard deviation (STD) have been used to evaluate the discriminatory power of the
circulation classifications. A ranking of circulation classifications has been
established for each region and for each metric. In the Atlantic and Northern
regions, classifications that show a better performance correspond to the same type
of algorithms, i.e. derived types with non-hierarchical cluster analysis. Instead,
in the Mediterranean region, classifications using pre-defined types based on
thresholds perform better. The classifications with the worst performance in every
region belong to the subjective type. An analysis of the impact of the number of CTs
on the discrimination ability of the classifications has also been carried out.
Depending on the metric used, a different sensitivity of the classifications to the
number of CTs has been found. The EV index shows an improvement when the number of
CTs increases. Instead, the PF and the STD metrics showed a negative impact with an
increasing number of CTs.