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Santa Ana Windflow in the Newhall Pass as Determined by an Analysis of Tree Deformation

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  • 1 Department of Geography, California State University, Northridge 91324
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Abstract

A tree deformation study was conducted in a suburban area of the Newhall Pass (located to the north of Los Angeles, California) to determine the direction and intensity of the Santa Ana windflow. Trees were used to provide the large data base necessary to study the windflow in rugged terrain in an area that is very vulnerable to the fire hazard presented by these winds.

To obtain a large data base, the study involved the use of several tree species. Comparison of the wind-direction data obtained from the trees correlates very closely with windvane data obtained in the study area. In measuring the intensity of the winds, a statistical deformation index was devised that is not affected by differing species response to the wind. This index is based upon the total number of trees per unit area that are deformed. It transforms the study of wind intensity–as reflected by the trees–from a largely qualitative judgement of the degree of tree deformation to a quantitative statistic.

With a careful consideration of non-wind effects which can deform the trees, studies of this type are very inexpensive and easy to conduct, providing an accurate climatological wind record as an adjunct to long-term meteorological data, especially in data-sparse regions.

Abstract

A tree deformation study was conducted in a suburban area of the Newhall Pass (located to the north of Los Angeles, California) to determine the direction and intensity of the Santa Ana windflow. Trees were used to provide the large data base necessary to study the windflow in rugged terrain in an area that is very vulnerable to the fire hazard presented by these winds.

To obtain a large data base, the study involved the use of several tree species. Comparison of the wind-direction data obtained from the trees correlates very closely with windvane data obtained in the study area. In measuring the intensity of the winds, a statistical deformation index was devised that is not affected by differing species response to the wind. This index is based upon the total number of trees per unit area that are deformed. It transforms the study of wind intensity–as reflected by the trees–from a largely qualitative judgement of the degree of tree deformation to a quantitative statistic.

With a careful consideration of non-wind effects which can deform the trees, studies of this type are very inexpensive and easy to conduct, providing an accurate climatological wind record as an adjunct to long-term meteorological data, especially in data-sparse regions.

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