2006 Volume 26 Issue 5 Pages 374-383
A multi-purpose field radiometer, MSR7000(Optical Research Corporation, Tokyo), was modified to be able to measure radiance and degree of polarization of the skylight either on the ground or on a ship (1nm interval, 5nm half width, IFOV=±1°, 415-1, 000nm). It is called MSR-M, which is Hyper Spectral Polarimeter. Measurements of maximum polarization, Pmax, are carried out to the direction of 90° from the sun in the principal plane, which is a plane determined by Sun, zenith and observation directions. The field data were taken at various sites such as the University of Alabama in Huntsville, off the coast and deserts in Nevada and California. Note that the deserts Nevada and Huntsville, Alabama, were under cloud free-conditions.
The main results are; (1) semi-transparent cloud appears to decrease Pmax values irrespective of wavelengths; (2) the soil of Railroad Valley, Nevada, indicate little polarization, but its reflectance increases monotonously with wavelengths-(Eventually Pmax decreases with wavelengths)-(3) a sharp drop of Pmax is noted at around 700nm under lawn cover due to the sharp drop of polarization degree and sharp increase of reflectance. -(The polarimeter with 6 channels could not detect these characteristics. Note that reflectance of soil and lawn indicates smooth change with wavelengths); and (4) Optical characteristics of aerosols were not apparently derived in these observations.