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United States Department of Agriculture

Agricultural Research Service

Title: Analysis of Seasonal, Climate, and Elevation Effects on Times Between Storms

Authors
item Bonta, James
item Hanson, Clayton
item Keefer, Timothy

Submitted to: Precipitation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 16, 2001
Publication Date: N/A

Interpretive Summary: "Storms" often need to be identified in a set of historic data for engineering uses, such as intensity-duration-frequency analysis, rainfall-erosivity factors for erosion estimation, structure design and other uses. Often a storm is identified by assigning a fixed dry time between bursts of rainfall for the entire record. However, it is known that this dry time between storms varies seasonally geographically and it also does not necessarily produce storm events that are statistically independent. In this study an estimation method is developed to compute a variable that is useful for identifying storms that account for season of year, climate and topography using data from Ohio, Arizona and Idaho. The minimum dry time between storms (critical dry-period duration, CD) is computed for arid, semiarid and humid locations, for mountainous terrain and for different seasons of the year. CD can be mathematically characterized for a large part of the US by knowing elevation and long-term average monthly and annual precipitation, all of which are generally available. The study has utility for drought preparedness and mitigation studies, risk analyses for agricultural crops and animals, computer simulation of rainfall events, etc.

Technical Abstract: "Storms" often need to be identified in a set of historic data for engineering uses, such as intensity-duration-frequency analysis, rainfall-erosivity factors for erosion estimation, structure design, and other uses. Often a storm is identified by assigning a fixed dry time between bursts of rainfall for the entire record. However, it is known that this dry time between storms varies seasonally, and it also does not necessarily produce storm events that are statistically independent. This study examines the use of a method to identify storms that accounts for season of year, climate, and topography. The minimum dry time between storms (critical dry-period duration) for arid, semiarid, and humid locations, and for mountainous terrain, and by season of year are determined by using an exponential distribution. The small-area spatial variability of critical duration (CD) within a climate is investigated, as well as the variation of CD with elevation at one site. Long records of short-time increment data (of the order of minutes) are scanty across the US. Consequently, relationships between CD and average monthly precipitation are evaluated for parameterizing the exponential distribution. The study has utility for drought preparedness and mitigation studies, risk analyses for agricultural crops and animals, stochastic simulation of rainfall events, etc.

Last Modified: 4/23/2014
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