The Relationship between Monthly Precipitation and Elevation in the Alberta Foothills during the Foothills Orographic Precipitation Experiment.

To better monitor and understand precipitation processes in the Alberta foothills, the Foothills Orographic Precipitation Experiment (FOPEX) was initiated in August 2001, consisting of six meteorological sites installed in a 40 km east-west transect in west-central Alberta to measure precipitation between 1070 and 2120 m above sea level. There are significant linear correlations between monthly accumulated precipitation and elevation when precipitation exceeds 70% of the long term average, but these relationships break down when monthly precipitation drops below the 70% threshold. During the cold season and when precipitation is greater than 70% of the long term mean, the altitudinal increase of monthly precipitation shows a linear dependency on the total amount of precipitation observed. Between October and April inclusive (cold season), accumulated precipitation increases by 74% for every 1000 m rise in elevation. However, for the cold months when precipitation is under the 70% threshold, this scaling factor is reduced to 46%. Spatial and topographic variability in precipitation during the warm season (May to September) makes it difficult to develop such a scaling factor. Based on these precipitation-elevation relationships, a simple but effective model is presented to extrapolate precipitation to various elevations along the transect using precipitation measured at a single location. [ABSTRACT FROM AUTHOR]