Resumen
A scientific experiment to investigate the atmospheric circulation, the mesoscale convective systems and the precipitation associated with the monsoon overnorthwestern mexico and southwestern united states was carried out during the northern summer of 1990. a number of institutions and universities participated in the experiment. special observations were made over the mexican states of Baja California, Baja California Sur, Sonora, Sinaloa, Durango, Coahuila, Chihuahua and in the United States, Arizona. a wide variety of metereological observations were made, including special pilot ballon and radiosonde soundings, research aircraft flights (including use of airborne doppler radar), special surface observations, as well as more routine satellite, surface and upper-air observations over the region. The observations have been processed and compiled bye the National Severa StormsLaboratory (NSSL) and the Center for Scientific Study and Higher Education of Ensenada (CICESE), in a data bank with the ooperation of Nationa Water Commission (CNA) and the Sonora Institute of Technology (ITSON). Different atmospheroc phenomena are being investigated, including the horizontal transport of water vapor and the studies to date using the 1990 data identify the ?Sierra Madre Occidental?, particularly important to the formation from the tropical Americas converge. The Mexican watersheds from the Pacific and the Gulf of California show higher precipitation over the Sierra madre, as compared with the watersheds from Chihuahua and the Gulf o Mexico, suggesting the Pacific ocean as the main source of moisture for monsoon circulation over northwestern Mexico.