Bulk Scattering Properties for the Remote Sensing of Ice Clouds. Part II: Narrowband Models

Abstract

This study examines the development of bulk single-scattering properties of ice clouds, including single scattering albedo, asymmetry factor, and phase function, for a set of 1117 particle size distributions obtained from analysis of FIRE-I, FIRE-II, ARM-IOP, TRMM-KWAJEX, and CRYSTAL-FACE data. The primary focus is to develop bandaveraged models appropriate for use by the MODIS imager on the EOS Terra and Aqua platforms, specifically for bands located at wavelengths of 0.65, 1.6, 2.1, and 3.75 µm.Our results indicate that there are substantial differences in the bulk scattering properties of ice clouds formed in areas of deep convection and those that exist in areas of much lower updraft velocities.Band-averaged bulk scattering property results obtained from a particle-size dependent mixture of ice crystal habits are compared to those obtained assuming only solid hexagonal columns. The single scattering albedo is lower for hexagonal columns than for a habit mixture for the 1.6, 2.1, and 3.75 µm bands, with the differences increasing with wavelength. In contrast, the asymmetry factors obtained from the habit mixture and only the solid hexagonal column are most different at 0.65 µm, with the differences decreasing as wavelength increases. At 3.75 µm, the asymmetry factor results from the two habit assumptions are almost indistinguishable. The asymmetry factor, single-scatter albedo, and scattering phase functions are also compared to the MODIS V1 models. Differences between the current and V1 models can be traced to the microphysical models, specifically the number of both the smallest and the largest particles assumed in the size distributions.3

Eyjafjallajökull volcano plume particle-type characterization from space-based multi-angle imaging

“…The vertical distributions of particles are based on plume height; aerosol is concentrated near-surface for control regions. 2 Gamma distribution is used for cirrus particle models, and r c is replaced by r e , the effective radius (Baum et al, 2005).…”

Single Particle Measurements of the Optical Properties of Small Ice Crystals and Heterogeneous Ice Nuclei

“…Several potential reasons for this exist. The first is that we are only measuring small ice crystals, whereas most other studies (Baum et al 2005b(Baum et al , 2010Curtis et al 2007Curtis et al , 2008 of the optical properties of ice crystals have been conducted on particles on the order of 100 mm where the shape of the particle is more easily determined and subsequently the particles' effect on the scattering of light is easier to observe.…”

Effects of atmospheric light scattering on spectroscopic observations of greenhouse gases from space. Part 2: Algorithm intercomparison in the GOSAT data processing for CO2 retrievals over TCCON sites

“…The four airborne particle types chosen are water cloud, ice cloud, and two different types of aerosol, corresponding to the aerosol types "2b" and "3b" of Kahn et al [2001]. The liquid water cloud has a Gamma size distribution [Hansen and Travis, 1974] of spherical drops with an effective radius of 8 mm, while the ice water cloud optical properties are taken from the model of Baum et al [2005aBaum et al [ , 2005b, assuming an effective particle radius of 70 mm. Type "2b" Kahn aerosol is a mixture of sulfate, sea salt, and course and fine-mode dust, while type "3b" Kahn aerosol is a mixture of sulfate and sea salt, and carbonaceous particles.…”

“…The a priori extinction profile for cirrus is also Gaussian-shaped but with height and width that are latitudinally dependent, based on Eguchi et al [2007], with a total optical depth of 0.05. The cloud optical properties are taken from Baum et al [2005b] for an effective radius of 60 mm. Aerosol and cloud extinction are retrieved as a log-value with an a priori covariance with a 1-s uncertainty of a factor of 50 at each level.…”