An Analysis of Rainfall in the Sonoran Desert and Adjacent Territory

An Analysis of Rainfall in the Sonoran Desert and Adjacent Territory

An Analysis of Rainfall in the Sonoran Desert and Adjacent Territory

An Analysis of Rainfall in the Sonoran Desert and Adjacent Territory

Excerpt

In arid regions rainfall is one of the most important physical conditions requisite to life, and its amount and seasonal distribution, its behavior and fate are pre-eminent in determining the distribution of plant and animal life.

For many years regular measurements of precipitation have been made by official and voluntary observers at a considerable number of localities in the arid Southwest. For over ten years the Desert Laboratory of the Carnegie Institution of Washington carried on investigations of rainfall. Periodic readings were made in unsettled but critical localities. The influence of topography on rainfall was studied on mountain ranges differing in mass and in total altitude. The gradients of precipitation with increasing altitude and the influences of slope exposure were studied. The variability of precipitation over small areas was investigated. Individual rainstorms were considered with reference to their origin, movement, duration, intensity, and relation to wind. Work was also done on runoff and soil moisture in connection with the study of precipitation.

The present publication is designed to summarize some of these investigations and to give their geographical bearing. The data used in the discussion include all those available for the Sonoran Desert and some of the adjacent climatically related areas.

The Sonoran Desert embraces the southwestern third of Arizona, extreme southeastern California, the western half of Sonora, and the lowland parts of Baja California north of the Cape Region. It lies almost wholly below an elevation of 3000 feet. Its boundary is shown in several of the charts accompanying this paper. The vegetation of the Sonoran Desert varies from low and open communities of drought-resistant shrubs to very open stands of low trees or heavier stands of shrubs and cacti. The vegetation of the most arid situations consists of two or three dominant perennial species, while that of the most favorable habitats includes from thirty to forty dominants of very dissimilar habit.

It has been demonstrated in this work that little essential advance can be made in the investigation of rainfall by continuation of readings at arbitrarily selected localities which happen to be centers of population. Intensive study of rainfall for a relatively short period at carefully selected critical localities would advance our knowledge far more than the continuation for many years of routine readings at sporadically located stations. Study of rainfall patterns in small areas and further study of topographic . . .

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