Determination of the Earth's emissivity for use in studies of global climate change

Abstract

A four-dimensional data assimilation program is being developed which uses measurements of the emissivity of vegetation canopies to define the Earth's surface temperature from remotely sensed measurements of radiance. Currently, there exists a paucity of data defining vegetative emissivity. The need for vegetative emissivity measurements in determining the global surface temperature from satellite radiances is established. The sensitivity of the radiance inversions to these data, however, is yet to be determined. The approach used to define the sensitivity of the inversion algorithms is presented. Provided also is the testbed developed to explore this sensitivity. A method to determine global surface temperatures given satellite radiance's and ground cover mosaics obtained from Landsat and Advanced High Resolution Radiometer (AVHRR) measurements using this sensitivity analysis is being investigated as part of this on-going study. A testbed and computer simulation to explore this sensitivity have been developed and tested. The satellite-infrared temperatures will be compared with canopy temperatures (in situ measurements) measured at ambient conditions away from direct sunlight exposure. Given this comparison, the accuracy of global maps of surface temperature obtained from satellite measurements of radiance can be defined when coupled with measurements of soil moisture and the known morphology of the vegetation.