Inversion of Multi-Angle Radiation Measurement

Observations of the polarization and reflectance in bands at 865 nm (negligible liquid water absorption) and 2250 nm (strong liquid water absorption) cannot be fitted by a simple atmospheric model consisting of a homogeneous cloud with a single particle size. If we use the polarization (polarized reflectance) measurements and the reflectance measurements to retrieve cloud particle size independently, we find that it is frequently (although not always) the case that the size retrieved with the polarization measurements is larger than the size retrieved using the reflectance measurements (Figure 1). Figure 1. Effective radius retrievals using polarized reflectance (blue) and reflectance with effective variances of 0.05, 0.1, 0.15, and 0.2 (mauve, turquoise, green, red). Polarized reflectance provides effective variance retrieval also. Retrievals use data taken on 25 July 2003 during the CSTRIPE field experiment and use research scanning polarimeter (RSP) data taken at 410, 865, and 2250 nm over stratocumulus clouds near Monterey. Retrievals were validated against in situ measurements and agree to within ±0.5 µm when an appropriate level in the cloud is used for comparison.