This project focuses on studying the processes in the earth's climate system that control the spatial coverage and year-to-year variation in the North American Monsoon System, which supports ecological and human systems from central Mexico through the southwestern United States. The study will use advanced computer models that combine weather forecasting with biological processes associated with the plants on the ground to determine how the highly variable monsoon rains control the spread of invasive grasses, including cheat grass and buffel grass, and the how the spread of these invasive grasses may, in turn, influence seasonal weather patterns and the monsoon system itself. Other aspects include the analysis of tree rings from across the southwest that will reveal historical patterns in the magnitude and distribution of the monsoons and also can be used to validate model predictions. The study will also explore how low elevation dry grasslands and high elevation forests compare with regard to cycles of wildfires. Summer rains are likely to influence the spread of fires from grasslands to forests and this study will help explain how this connection is influenced by variability in the monsoon rains. Finally, an effort will made to extend understanding of what controls monsoon rains to include natural cycles in climate, such as those associated with the two-to-seven year El Nino cycle and the Pacific Decadal Oscillation, both of which affect surface temperatures of the Pacific Ocean. This is a search for the ultimate causes of the coupling between monsoon rains and the ecological systems in the region. For example, a main objective will be to explore the nature of the climate and ecological forces that define the spatial extent of the monsoon system, and the ocean processes and cycles that define its magnitude and long-term variation. The participants in this large and integrated project include ecologists and climate scientists working together, from both the U.S. and Mexico.
This project will have broader impacts to science and society in several ways. Six post-doctoral students and seven graduate students will be trained. A Discovery Fellows program will be created through the Laboratory of Tree Ring Research that will hire six school teachers, including some from the Navajo Nation, who will be involved in assembling a tree ring archive for the southwest. A process will be established to develop a new regional land surface computer model that will be administered by the National Center for Atmospheric Research and made widely available for use. A bi-national collaboration with Mexico will be started that will include extended visits each year with scientists and graduate students. Finally, a display will be created that describes the relevance of summer monsoons to Native American groups and contemporary societies; it will be housed and shown at the Biosphere 2 Center in Tucson, which hosts about 75,000 visitors each year.
