MODELS OF SPATIAL AND TEMPORAL DISTRIBUTION OF THUNDERSTORM RAINFALL
A simplified stochastic model based on airmass thunderstorm rainfall data from the 58-square-mile Walnut Gulch Experimental Watershed in south eastern Arizona is being developed at the Southwest Watershed Research Center, Tucson, Ariz. Records from the 95 rain gage network on this watershed pro vide valuable information on airmass thunderstorm rainfall in the Southwestern United States. Proba bility distributions are being used to model random variables—number of cells, spatial distribution of the cells, and cell center depths—of thunderstorms in a summer rainy season. A computer program produces synthetic thunderstorm rainfall based on these distributional assumptions. The synthetic data are compared, with respect to storm center depths and isohyetal map characteristics, with data from the dense rain gage network on Walnut Gulch. The daily and hourly chances of occurrence of seasonal airmass thunderstorm rainfall are modeled. Efforts are being made to model the temporal dis tribution of rainfall from individual cells within the airmass thunderstorm. Finally, the question of model transferability to other regions and locations is tied to defining regional meteorology and local topography.
Simulation of runoff-producing rainfall in the Southwest
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Indian Fig Cactus (Opuntia Ficus-Indica (L.) Miller) in the Americas: an Uncertain History
Abstract: 
 Opuntia ficus-indica (L.) Miller is a globally important cactus species with a long history of human use. In addition to the importance of O. ficus-indica as a food for humans and livestock, it also has long served a role in the production of cochineal, a once important textile dye. This cactus also is intimately interwoven into the story of Cactoblastis cactorum (Berg) (South American cactus moth), one of the best-known examples of biological weed control. In this regard, O. ficus-indica has been a target weed as well as an unintended host in C. cactorum invasion. Although the distribution and human-assisted movement of this cactus throughout much of the world is well documented, surprisingly little has been written about its history and movement within the Americas. Literature associated with Opuntia and their phytophagous pests in North and South America was examined in an attempt to determine the history of O. ficus-indica in the Americas. Available information suggests with some certainty that O. ficus-indica originated in present-day Mexico, but the timing of its introduction to South America is much less clear. Taxonomic difficulties associated with distinguishing among Opuntia species and the long pre-Columbian history of exchange between South American and Mesoamerican cultures are two primary complicating factors associated with dating the dispersal of this species to South America. Additionally, previous evidence in support of a pre-Columbian introduction to South America relied on questionable identification of insect-based textile dyes. These uncertainties are significant because clearer knowledge of the history of O. ficus-indica introduction to South America could provide a more complete biological and ecological context to efforts at managing this species in its native and introduced ranges, particularly with respect to the threat posed by C. cactorum in North American and Argentinean plantations.