Submitted to: Remote Sensing in Hydrology Symposium
Publication Type: Proceedings
Publication Acceptance Date: February 15, 2001
Publication Date: April 2, 2000
Interpretive Summary: The ability to reliably assess effects of global climate change on water resources for agricultural production on regional scales requires appropriate integration of remotely sensed data and ground observations. A semi-empirical model coupling NOAA AVHRR data with surface climate data is evaluated to assess regional estimates of evapotranspiration (ET) in central Iowa. Surface flux measurements of ET at several locations provide the data for calibrating the model. Results show evapotranspiration estimates from the model to be consistent with the magnitudes of measurements at local scales.
Technical Abstract: A study was conducted to map regional evapotranspiration (ET) from ground based climate data and remote sensing data acquired form NOAA AVHRR satellite platform. The net short- and long wave radiation balance was derived from AVHRR data. Sensible heat flux was estimated from a semi-empirical model and the ET was estimated as a residual factor. The net tradiation balance and evapotranspiration for Iowa were mapped for 10 relatively clear days during the 1990 crop season. The field experiment conducted at Treynor was instrumental in defining the coefficients used in the ET model. The model coefficients determined from simultaneous field and satellite observations. ET was higher in the southeastern part of the state and lower in the north central and western areas. The NDVI image does not provide the contrast or expected range of crop conditions. The ET images appear to magnify the differences in crop moisture conditions. Additional research is necessary to demonstrate the reliability of the semi-empirical model in defining drought conditions.