The indicatrices of solar radiation reflected from characteristic natural surfaces were measured with a Nimbus Medium Resolution Radiometer (MRIR) 3 m above the ground. Results indicated that areas such as salt and alkali flats had only small deviations from isotropic reflections, while others such as sparsely vegetated areas had substantial deviations. The indicatrices were strongly dependent on the sun angle; thus a daily variation was found for most features. Typical indicatrices, normalized to nadir angle of zero degrees, are presented along with their impacts on measured albedo, which varies with solar angle. Our results can (1) improve surface albedo considerations using space-generated data, and (2) serve as a more realistic lower boundary condition for atmospheric transfer determinations based on space data.
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Article tables are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Integrated effect of solar spectrum, surface spectral characteristic, and spectral sensitivity of Nimbus Channel 5.
Integrated effect of solar spectrum and surface spectral characteristic.
Table IV
Estimates of Possible Effects Producing Differences In the Calibration Constants (Slopes for Different Surfaces)
Possible error due to effect (%)
Possible effects
Salt Flats vs green plants
Salt Flats vs soil
Temperature effect
+0.0–4.5
+0.0–4.5
Degradation of instrument during study period
0.0 (negligible)
0.0 (negligible)
Pyranometer spectral response
−0.4
−0.3
Spectral characteristics of surface interacting with spectral sensitivity of MRIR
+6.1
+11.6
Change in spectral sensitivity of MRIR from time of manufacture
(a) oxidation of reflecting surfaces
+3.3
+5.7
(b) degradation or drift of Infrasil Quartz Filter, electronics, etc.
?
?
Total (temperature effect included)
14.3
22.1
Total (temperature effect not included)
9.8
17.6
Slope of curve (actually measured)
12.8
37.6
Unexplained (temperature effect included)
−1.5
15.5
Unexplained (temperature effect not included)
3.0
20.0
Table V
Dates and Solar Elevation Angles for All Measured Indicatrices
Integrated effect of solar spectrum, surface spectral characteristic, and spectral sensitivity of Nimbus Channel 5.
Integrated effect of solar spectrum and surface spectral characteristic.
Table IV
Estimates of Possible Effects Producing Differences In the Calibration Constants (Slopes for Different Surfaces)
Possible error due to effect (%)
Possible effects
Salt Flats vs green plants
Salt Flats vs soil
Temperature effect
+0.0–4.5
+0.0–4.5
Degradation of instrument during study period
0.0 (negligible)
0.0 (negligible)
Pyranometer spectral response
−0.4
−0.3
Spectral characteristics of surface interacting with spectral sensitivity of MRIR
+6.1
+11.6
Change in spectral sensitivity of MRIR from time of manufacture
(a) oxidation of reflecting surfaces
+3.3
+5.7
(b) degradation or drift of Infrasil Quartz Filter, electronics, etc.
?
?
Total (temperature effect included)
14.3
22.1
Total (temperature effect not included)
9.8
17.6
Slope of curve (actually measured)
12.8
37.6
Unexplained (temperature effect included)
−1.5
15.5
Unexplained (temperature effect not included)
3.0
20.0
Table V
Dates and Solar Elevation Angles for All Measured Indicatrices
Add to BibSonomy