Determination of spring onset and growing season leaf development using satellite measurements

An integrated approach to retrieve microwave emissivity difference vegetation index (EDVI) over land regions has been developed from combined multi-platform/multi-sensor satellite measurements, including SSM/I measurements. A possible relationship of the remotely sensed EDVI and the leaf physiology of canopy is explored at the Harvard Forest site for two growing seasons. This study finds that the EDVI is sensitive to leaf development through vegetation water content of the crown layer of the forest canopy, and has demonstrated that the spring onset and growing season duration can be determined accurately from the time series of satellite estimated EDVI within uncertainties of approximately 3 and 7 days for spring onset and growing season duration, respectively, compared to in situ observations. The leaf growing stage can also be monitored by a normalized EDVI. EDVI retrievals from satellite generally are possible during both daytime and nighttime when it is not raining. The EDVI technique studied here may provide higher temporal resolution observations for monitoring the onset of spring, the duration of growing season, and leaf development stage compared to current operational satellite methods.