A simple method of computing the variation of annual precipitation over mountainous terrain

✍ Scribed by Maurice Danard

• Book ID: 104657907
• Publisher: Springer
• Year: 1971
• Tongue: English
• Weight: 728 KB
• Volume: 2
• Category: Article
• ISSN: 0006-8314
• DOI: 10.1007/bf00192129

✦ Synopsis

A method for computing the distribution of annual precipitation for mountainous areas is presented. As a pilot study, the South Thompson River basin in British Columbia is examined. In addition to data from climatological (valley) stations, annual precipitation is estimated for snow course (mountain) locations from the water equivalent of the snowpack on April 1.

An equation for the dependence of precipitation amount on orography is derived from simple physical considerations. Regression equations based on this are then computed and the calculated precipitation is checked with runoff data. A basic predictor is the mean vertical water vapor transport through a horizontal unit area due to flow over undulating terrain. This depends on the average slope of a region 3 deg long by 2 deg lat centered on each grid point. The transport at the earth's surface has a simple correlation coefficient with the combined valley and mountain precipitation data of 0.76. When the transport is computed at the mean cloud base (taken as 1800 m above sea-level), the correlation coefficient rises to 0.87.