Atmospheric circulation influence on the interannual variability of snow pack in the Spanish Pyrenees during the second half of the 20th century

摘要: Large areas in the Spanish Pyrenees are covered by snow between December and April, especially above 1650 m a.s.l., location of cold season 0°C isotherm. However, a significant negative trend Pyrenean pack was detected during second half 20th century. This paper analyses interannual evolution accumulation these mountains relation to variability atmospheric circulation. The study considers two spatial scales, from weather types over Iberian Peninsula hemispheric patterns. results show strong relationships annual occurrence several spring accumulation. Changes frequency explained large scale circulation patterns, North Atlantic Oscillation (NAO). Thus, positive observed NAO index leads decrease that favour an increase unfavourable conditions for