HR: 09:15h
AN: H11H-06    [Abstracts]
TI: Changes in Vegetation and Surface Fluxes Associated with the North American Monsoon in 2004
AU: * Watts, C
EM: watts@fisica.uson.mx
AF: University of Sonora, Blvd. Encinas y Rosales, Hermosillo, Son 83000 Mexico
AU: Rodriguez, J C
EM: jcrod2001@yahoo.com
AF: IMADES, Resyed y Aguascalientes, Hermosillo, Son 83190 Mexico
AU: Garatuza-Payan, J
EM: garatuza@itson.mx
AF: ITSON, 5 de Febrero, Cd Obregon, Son 85000 Mexico
AU: Fouglas, M
EM: michael.douglas@noaa.gov
AF: NOAA-NSSL, 1313 Halley Circle, Norman, OK 73069
AU: Scott, R
EM: rscott@tucson.ars.ag.gov
AF: USDA-ARS-SWRC, 2000 E Allen Road, Tucson, AZ 85715
AB: Observations show that the onset of summer rains occurs in late June over northwestern Mexico, and that the greatest rainfall over the foothills of the Sierra Madre Occidental occurs in July. The region of maximum rainfall migrates oceanward with time such that by September the greatest rainfall is along the coastal region, with noticeably less rainfall inland. The onset of the rains is accompanied by a rapid leafout of the vegetation with an associated increase in evapotranspiration. We hypothesize that the rapid increase in foliage, quantified by the leaf area index, has a feedback on the atmospheric radiation balance in the surface layer which in turn affects the maximum temperature of the inland terrain. Thus the boundary layer undergoes a rapid transition from a deep well-mixed dry layer during the pre-monsoon period to a shallower, but much more humid layer during the post-onset. The changes in the vegetation characteristics during the onset period, together with the seasonal increase in the Gulf of California SSTs contribute to a seasonal march of the region of maximum precipitation towards the coastal areas and away from the mountain slopes as the summer progresses. The North American Monsoon Experiment (NAME) provides an excellent opportunity to study this problem. During the Enhanced Observation Period in the summer of 2004, the existing operational networks of upper air soundings and precipitation were significantly improved for the core monsoon region. In addition 3 micrometeorological towers were installed to provide information about the surface fluxes throughout the monsoon development. Preliminary results will be presented and related to changes in vegetation which were monitored using MODIS satellite images.
DE: 1818 Evapotranspiration
DE: 1640 Remote sensing
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting