Recent variations of snowpack depth in the central Spanish Pyrenees

The evolution of snow depth in the central Spanish Pyrenees was analyzed using measurements from 106 snow stakes over a period of 14 yr (1985-1999). Relationships were considered between the regional series of snow depths at the end of winter and in the middle of spring with respect to precipitation and temperature in previous months. Both variables explained a large percentage of the interannual variability in snowpack. The high correlation between climate parameters and snow depth series may help to better understanding snow evolution at different times of the year and to obtain a predicted series of snow depths for the period 1950-1999 from longer climate series. Snow depth decreased significantly during the second half of 20th century, probably because there was less precipitation from January to March. The decrease in winter precipitation seemed to be related with the positive trend of the North Atlantic Oscillation (NAO) index during the same period.