CONVERSION OF NADIR, NARROW-BAND REFLECTANCE IN RED AND NEAR-INFRAREDCHANNELS TO HEMISPHERICAL SURFACE ALBEDO

Measured nadir-viewed narrow-bond reflectances rn red and near infrare d channels simulating AVHRR Channels 1 and 2 are compared with measure d integrated solar spectrum hemispherical albedo. Reflectances and alb edos rc;ere measured from an aircraft over four widely different veget ation surfaces in southeastern Tasmania (Australia). A linear function is used to simultaneously correct for narrow band to broad band conve rsion errors and to convert nadir viewed reflectances to hemispherical albedos. While the application of the conversion equation presented i s limited to the vegetation types of the study, the equation is indepe ndent of vegetation type. Results indicate that the reflectance front the rough surface of a forest canopy is not Lambertian and that the us e of a directional to hemispherical albedo conversion using a Lamberti an assumption may lead to errors as great as 35%. (C) Elsevier Science Inc., 1997.