|Holifield Collins, Chandra|
Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/20/2003
Publication Date: 12/20/2003
Citation: AGU Winter Meeting, San Fransisco, CA., Abstracts, unpaginated.
Technical Abstract: The daily net carbon dioxide (CO2) flux from extensive grassland ecosystems is an important component of the global carbon cycle. In previous studies, instantaneous net CO2 flux was estimated using a Water Deficit Index (WDI) determined from the relation between surface reflectance and temperature. The mean absolute difference between measured and WDI-derived CO2 flux was 0.23 over a range of CO2 flux values from -0.10 to 1.10 (mg m-2 s-1). The objective of this study was to determine daily net CO2 flux from instantaneous estimates for a semiarid grassland site in Southeast Arizona. This objective was reached through two main steps. First, a linear relationship (R2 = 0.95) was found between instantaneous net CO2 flux and net daytime (6 a.m. to 6 p.m.) flux and used to generate maps of daytime CO2 flux. Second, a field study was conducted to relate night time flux measurements to daytime measurements. These relations made it possible to map daily (24-hour) net CO2 flux from a single satellite image and basic meteorological information. A limitation of this approach is the dependence upon empirical relations for deriving daytime and night time estimates from instantaneous measurements. On the other hand, the empirical relations derived at this location were strong and consistent for the six-year study period.