An objective circulation pattern classification for the region of Svalbard

摘要

This study presents an automated or so-called objective circulation pattern classification for the region of the Svalbard archipelago on the basis of gridded NCEP/NCAR-reanalysis data in a spatial resolution of 2.5×2.5° for the variables sea level pressure and geopotential heights on the 500 and 700hPa levels. Self-organizing maps were set up and run several times, each time using a different number of clusters into which to partition the data. After evaluating the results for all clusters by means of statistical indices we decided to use nine circulation patterns for further analysis. The resulting patterns were related to surface variables for Svalbard in order to test how good the catalogue of circulation patterns performs as a tool for the analysis of synoptic forcing. Furthermore, the catalogue was compared to an alternative subjective classification of weather types which results in only partly coherence. We show that the different circulation patterns derived in this study nicely represent seasonal states of the atmosphere. Within seasons, significant deviations of surface air temperature and precipitable water content are associated with the different weather types. The latter fact points to a broad applicability of this circulation pattern classification for studies that address the impact of interannual atmospheric variability on other parts of the geo-system such as glaciers, ice caps and vegetational patterns.