Backscattering albedo

A. L. Oldenburg et al., Plasmon-resonant gold nanorods as low backscattering albedo contrast agents for optical coherence tomography. Optics Express, 14(15), 6724-6738 (2006). 

Ferrare R. A., Meffi S. H., Whiteman D. N., Evans K. D., Poellot M., and Kaufman Y. J. (1998b) Raman hdar measurements of aerosol extinction and backscattering 2. Derivation of aerosol real refractive index, single-scattering albedo, and humidification factor using Raman hdar and aircraft size distribution measurements. J. Geophys. Res. 103, 19673-19689. 

Vertical distribution of aerosols extinction coefficient, backscattering coefficient, single scattering albedo. 

It was mentioned in Chapter 4 that aerosol particles scatter and absorb solar radiation. These processes depend upon the concentration, size distribution, form, refractive index and absorption coefficient of the particles, as well as upon the wavelength of the radiation. In the case of water-soluble particles the extinction is also controlled by relative humidity (see Section 4.5). The energy absorbed by particles leads to an increase of temperature, while backscattering produces an energy loss for the system. Sines this energy loss may be characterized by the albedo, it is proposed to examine first the relation between albedo and temperature in surface air. 

Boucher, O., and Lohmann, U. (1995) The sulfate-CCN-cloud albedo effect, Tellus 47B, 281-300. Charlson, R. J., Langner, J., Rodhe, H., Leovy, C. B., and Warren, S. G. (1991) Perturbation of the northern hemisphere radiative balance by backscattering from anthropogenic sulfate aerosols,... 

Photometric and polarimetric data obtained from telescopic observations and laboratory measurements at small phase angles have been accnmnlating for many years however, the interpretation of these effects, especially of the polarization branch, was not satisfactory until recently [7-20] when the coherent backscattering (interference) mechanism was developed to explain both effects. Since that time, additional experimental [21-23] and theoretical [18, 24-28] data were obtained, showing that the effects are more complex than initially considered. For example, negative polarization branches with two minima were discovered for some Jupiter satellites and bright asteroids [29,30], and unusual behavior of the opposition spike amphtude with albedo for the Moon, asteroids, and Jupiter s satellite Europa were found [31-33]. 

In general, a decrease of the opposition spike amplitude with increasing albedo contradicts the coherent backscattering mechanism that predicts an increase of the spike amplitude with increasing albedo. One possible explanation of this contradiction is that with the albedo increase, the width of the spike becomes significantly smaller than 0.1° and the phase ratio 7(0.1°)//(3°) is not sensitive to this spike. 

Figure 1. Dependence of bolometrie albedo on phase angle. The data are from (0) [15], (1) [16], (2-7) [8], (8) [13]. The solid line represents the least-square fit to the data for comets C/1975 VI (West) and C/1980 Y1 (Bradfield) and is interpolated to eonneet smoothly to the backscattering curve from [13] normalized at a = 30°. The data from [13] are normalized to the data for comet Bradfield at a = 127°.

Note that the opposite choices are usually made in oceanographic research, during analysis of oceanic albedo. In this case, the backscattered photons have significant effects therefore, a description of the phytoplankton heterogeneity is required. In order to numerically solve Maxwell s equations for the heterogeneous particles, such models usually simplify the description of the shapes by means of the equivalent sphere approximation (see Bernard et al., 2009 for an example of core-shell model). 

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