Rainfall frequency: An aspect of climatic variation

Analyses which have been made in the past have shown no significant trend in annual values of rainfall during the period of rainfall records in the southwestern United States. In the present study, frequency of daily rains of various sizes are analyzed for four long-record stations in New Mexico. It is shown that the frequency of rains smaller than 0.50 inch in a day progressively increased from 1850 to about 1930. Opposite trends in different size classes tended to partially compensate one another in such a way that trends do not appear in the annual rainfall totals. Frequency of rains of various sizes comprising wet years and dry are compared. Some effects of changes in rainfall frequency on vegetation and erosion are discussed.