The suggestion that polarimetry is the right tool to reliably constrain the aerosol radiative forcing is based on both scientific and instrumental considerations. The scientific basis for such a contention is theoretical modeling of the scattering of light by spherical and non-spherical particles. This has demonstrated the variation of polarization with scattering angle and wavelength to be extremely informative about the size, refractive index and shape of aerosol particles. Moreover these polarization features in scattered radiation are less affected by multiple scattering than intensity features are. The principal instrumental problem in the reliable retrieval of aerosol properties is the sensitivity of the retrieval process to instrumental calibration.
Polarization is a relative measurement which allows for simple and extremely accurate calibration.
There are therefore two requirements for the effective use of polarization measurements. First, that measurements are made over a broad range of scattering angles and a wide range of wavelengths so that the full information content in the scattered radiation is observed. Second, that the instrument be well calibrated. Demonstrations that polarimetric data from the RSP instrument can realize the true potential of polarimetry to retrieve aerosol and clouds properties are given in the Data and Analysis section,while the text of an SPIE Proceeding describing the calibration of the RSP is available in Postscript form. For more information regarding the RSP instrument and its use please contact Dr. Brian Cairns .