Using scattering calculations to compare MODIS retrievals of thin cirrus optical properties with SAM solar disk and aureole radiance measurements

DeVore, John; Stair, A. T.; LePage, Andrew J.; Villanucci, D. P.

doi:10.1029/2011jd015858

Cited by 12 publications

(23 citation statements)

References 28 publications

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“…Further, τ c tends to be larger than that reported by the SAM. This is in line with DeVore et al (2012), who found that the τ SAM needs to be corrected upward to account for forward scattering of ice crystals. The simulated radiances are compared with the selected SAM measurements in Figs.…”

Section: Summary Of Sensitivity Testssupporting

confidence: 49%

“…The impacts on near-forward scattered radiation due to ice crystal roughness and habit have also been considered (DeVore et al, 2012;Segal-Rosenheimer et al, 2013;Reinhardt et al, 2014). However, the present study extends the knowledge gained in previous research (DeVore et al, 2009(DeVore et al, , 2012Segal-Rosenheimer et al, 2013;Wilbert et al, 2013;Reinhardt, 2013;Reinhardt et al, 2014) as we simulate in detail the angular distribution of phase function and radiances instead of circumsolar irradiances integrated over some angular range (as in Reinhardt et al, 2014). The potential applications of these results include remote sensing of optical thickness, ice cloud properties based on the radiance field near the sun, and the design of concentrating solar energy applications.…”

Section: Summary Of Sensitivity Testsmentioning

confidence: 99%

“…However, the studies of Segal-Rosenheimer et al (2013) and Reinhardt et al (2014) have revealed that differences in the modeled forward scattering of smooth and roughened ice crystals as well as different shape distributions of ice crystals lead to differences in the circumsolar radiation. DeVore et al (2012) also noted the impact of ice crystals properties (roughness and effective radius) on calculated circumsolar radiances.…”

Section: Introductionmentioning

confidence: 99%

“…SAM measures the disk and circumsolar radiances with a very high dynamic range and produces the disk and aureole radiances as a function of angle from the center of the sun out to 8 • with an angular resolution of 0.0148 • . DeVore et al (2009) demonstrated the ability of SAM measurements to derive the effective radius and optical thickness of ice clouds and DeVore et al (2012) used MODIS retrievals of thin cirrus to calculate solar disk and aureole measurements that were compared with SAM measurements. Reinhardt et al (2014) have also developed a method to determine circumsolar radiation from satellite observations.…”

Section: Introductionmentioning

confidence: 99%

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Disk and circumsolar radiances in the presence of ice clouds

et al. 2017

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Abstract. The impact of ice clouds on solar disk and circumsolar radiances is investigated using a Monte Carlo radiative transfer model. The monochromatic direct and diffuse radiances are simulated at angles of 0 to 8 • from the center of the sun. Input data for the model are derived from measurements conducted during the 2010 Small Particles in Cirrus (SPAR-TICUS) campaign together with state-of-the-art databases of optical properties of ice crystals and aerosols. For selected cases, the simulated radiances are compared with groundbased radiance measurements obtained by the Sun and Aureole Measurements (SAM) instrument.First, the sensitivity of the radiances to the ice cloud properties and aerosol optical thickness is addressed. The angular dependence of the disk and circumsolar radiances is found to be most sensitive to assumptions about ice crystal roughness (or, more generally, non-ideal features of ice crystals) and size distribution, with ice crystal habit playing a somewhat smaller role. Second, in comparisons with SAM data, the ice cloud optical thickness is adjusted for each case so that the simulated radiances agree closely (i.e., within 3 %) with the measured disk radiances. Circumsolar radiances at angles larger than ≈ 3 • are systematically underestimated when assuming smooth ice crystals, whereas the agreement with the measurements is better when rough ice crystals are assumed. Our results suggest that it may well be possible to infer the particle roughness directly from ground-based SAM measurements. In addition, the results show the necessity of correcting the ground-based measurements of direct radiation for the presence of diffuse radiation in the instrument's field of view, in particular in the presence of ice clouds.

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Section: Summary Of Sensitivity Testssupporting

confidence: 49%

Section: Summary Of Sensitivity Testsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Disk and circumsolar radiances in the presence of ice clouds

et al. 2017

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“…Ice clouds consist almost exclusively of non-spherical ice crystals with various shapes (i.e., habits) and sizes (e.g., Liou, 1986). To determine the influences of ice clouds on solar and infrared radiation as required for numerical models and remote sensing retrievals, knowledge of single-scattering properties of ice crystals is required (e.g., Fu, 1996Fu, , 2007McFarquhar et al, 2002;Baum et al, 2011;Baran, 2012;DeVore et al, 2012;Yang et al, 2013;Yi et al, 2013;Um and McFarquhar, 2013;Cole et al, 2014;van Diedenhoven et al, 2014a).…”

Section: Introductionmentioning

confidence: 99%

Dimensions and aspect ratios of natural ice crystals

McFarquhar

Hong

et al. 2015

Atmos. Chem. Phys.

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Abstract. During the 2006 Tropical Warm Pool InternationalCloud Experiment (TWP-ICE) in the tropics, the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) in the Arctic, and the 2010 Small PARTicles In CirrUS (SPAR-TICUS) campaign at mid-latitudes, high-resolution images of ice crystals were recorded by a Cloud Particle Imager at temperatures (T ) between −87 and 0 • C. The projected maximum dimension (D ), length (L ), and width (W ) of pristine columns, plates, and component bullets of bullet rosettes were measured using newly developed software, the Ice Crystal Ruler. The number of bullets in each bullet rosette was also measured. Column crystals were further distinguished as either horizontally oriented columns or columns with other orientations to eliminate any orientation effect on the measured dimensions. The dimensions and aspect ratios (AR, the dimension of the major axis divided by the dimension of the minor axis) of crystals were determined as functions of temperature, geophysical location, and type of cirrus.Dimensions of crystals generally increased with temperature. Columns and bullets had larger dimensions (i.e., W ) of the minor axis (i.e., a axis) for a given dimension (i.e., D or L ) of the major axis (i.e., c axis), and thus smaller AR, as T increased, whereas this trend did not occur for plate crystals. The average number of branches in bullet rosettes was 5.50 ± 1.35 during three campaigns and 6.32 ± 1.34 (5.46 ± 1.34; 4.95 ± 1.01) during TWP-ICE (SPARTICUS; ISDAC). The AR of bullets increased with the number of branches in bullet rosettes. Most dimensions of crystals and ARs of columnar crystals measured during SPARTICUS were larger than those measured during TWP-ICE and IS-DAC at −67 < T < −35 • C and at −40 < T < −15 • C, respectively. The relative occurrence of varying pristine habits depended strongly on cirrus type (i.e., anvil or non-anvil clouds), with plates especially occurring more frequently in anvils. The L-W relationships of columns derived using current data exhibited a strong dependence on temperature; similar relationships determined in previous studies were within the range of the current data.

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Retrieval of cirrus properties by Sun photometry: A new perspective on an old issue

et al. 2013

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[1] Cirrus clouds are important modulators of the Earth radiation budget and continue to be one of the most uncertain components in weather and climate modeling. Sun photometers are widely accepted as one of the most accurate platforms for measuring clear sky aerosol optical depth (AOD). However, interpretation of their measurements is ambiguous in the presence of cirrus. Derivation of a valid AOD under cirrus conditions was focused previously on correction factors, rather than on derivation of cirrus cloud optical thickness (COT). In the present work, we propose a new approach that uses the total measured irradiance to derive cirrus COT and ice particle effective diameter (D eff ). For this approach, we generate lookup tables (LUTs) of total transmittance for the Sun photometer field of view (FOV) due to the direct and scattered irradiance over the spectral range of 400-2200 nm, for a range of cirrus COT (0-4), and a range of ice cloud effective diameters (10-120 mm) by using explicit cirrus optical property models for (a) cirrus only and (b) a two-component model including cirrus and aerosols. The new approach is tested on two cases (airborne and ground-based) using measured transmittances from the 14-channel NASA Ames Airborne Tracking Sun photometer. We find that relative uncertainties in COT are much smaller than those for D eff . This study shows that for optically thin cirrus cases (COT < 1.0), the aerosol layer between the instrument and the cloud plays an important role, especially in derivation of D eff . Additionally, the choice of the cirrus model may introduce large differences in derived D eff .

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Using scattering calculations to compare MODIS retrievals of thin cirrus optical properties with SAM solar disk and aureole radiance measurements

Cited by 12 publications

References 28 publications

Disk and circumsolar radiances in the presence of ice clouds

Disk and circumsolar radiances in the presence of ice clouds

Dimensions and aspect ratios of natural ice crystals

Retrieval of cirrus properties by Sun photometry: A new perspective on an old issue

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