Dominant factors influencing precipitation efficiency in a continental mid-latitude location

Studies of precipitation efficiency (PE), which is generally defined as the ratio of total precipitation to the total of available moisture, have been conducted for more than 50 years. In that time, many factors influencing PE value have been encountered. Some of them have been widely accepted while the rest are still in debate.

Knowing some of those factors, it has been generalized that PE values are varied with seasons and rainfall systems (convection vs. startiform) without establishing any observational experiment to prove them. Therefore, this study was conducted in order to support both assertions. Rainfall at Sanborn Field, Columbia, MO, was monitored for one year to represent a continental Mid-Latitude location, with data collected from October 2003 till September 2004. PE values for these events were calculated using the water budget method introduced by previous investigators.

The results indicate that the average PE value varied with season and rainfall system, which support the general statement proposed. The highest value was calculated during summer and lowest in winter, while convective rainfall had higher PE values than the startiform ones. Additionally, PE is compared to environmental factors to determine if any relationship exists, and three case studies are conducted to distinguish the behavior of three different PE regimes.