A three-year study by Desert Research Institute scientists has strongly linked the rise in sea surface temperatures in the Gulf of California with the timing, intensity and extent of the North American or Mexico Monsoon, considered one of the region's most dependable weather patterns. Dr. David Mitchell of DRI presented the study's findings July 27 at the International Union of Geodesy and Geophysics in Birmingham, England.
The monsoon is important to the region, providing up to 45 percent of annual precipitation for Arizona and New Mexico, and about 60 percent of northern Mexico's rainfall, between early July and mid-September. A strong monsoon has also been linked to summer droughts in the U.S. Midwest and to dry conditions in southern California the preceding winter.
Using satellite remote sensing to track sea surface temperatures in the northern Gulf of California, Mitchell, and DRI colleagues Dr. Tim Brown and graduate research assistant Dorothea Ivanova, observed that the monsoon rains typically would not begin until the temperature reached and maintained at least 26 C (79 F). The amount of precipitation that results also correlates to the gradual increase in sea surface temperatures, with the increase in rainfall in the U.S. generally lagging five to 15 days behind rises in sea surface temperature
Mitchell said Arizona and New Mexico received two-thirds of their rainfall after sea surface temperatures in the northern part of the gulf exceeded 29 C (84 F). He suggests the change in sea surface temperatures may serve as a possible forecasting tool for monsoon rains in the Desert Southwest. He said relevant data from the past 26 years reinforces the relationship between rising sea temperature and increased rainfall.
Mitchell and Brown point to recent oceanographic studies that indicate a warm coastal current in the Gulf of California may be responsible for heating the water above levels that can be attributed solely to the sun's energy.