• snow level;
  • warming;
  • Arizona;
  • water resources;
  • trends


Trends in daily mountain snow levels over two key watersheds in central Arizona were established for the last 70 years. Snowfall levels were approximated using two methods: (1) an empirical method based on daily snowfall and precipitation data from an array of National Weather Service Cooperative (COOP) Network stations at a range of elevations, and (2) a theoretical method based on the calculation of the wet-bulb zero (WBZ) height using nearby rawindsonde atmospheric profile data. A trend towards a higher WBZ height since water year 1960 is evident, as is a highly significant trend in the percentage of days in which the snow level was above stations with elevations between 1095 and 2166 m since water year 1934. The two snow level variables are significantly positively related to air temperature. This could be problematic in a region where the population is dependent upon the efficiency of snow in generating runoff for replenishing ground and surface water supplies. Copyright © 2009 Royal Meteorological Society