Effects of Cloud Horizontal Inhomogeneity on the Optical Thickness Retrieved from Moderate-Resolution Satellite Data

Iwabuchi, Hironobu; Hayasaka, Tadahiro

doi:10.1175/1520-0469(2002)059<2227:eochio>2.0.co;2

Cited by 89 publications

(82 citation statements)

References 39 publications

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“…When the sun incidence angle is large (60°), It increases as scattering angles decrease below 100° and 110°. This decrease were already observed and simulated at the scale of 1kmx1km in previous studies [7,8] and is imputable to shadowing effects. On contrary, the increase of COT with the sun incidence angles, which was observed in several studies [1,3], is not reproduced here.…”

Section: D Errors On Retrieved Cloud Optical Propertiessupporting

confidence: 74%

Evaluation of cloud heterogeneity effects on total and polarized visible radiances as measured by POLDER/PARASOL and consequences for retrieved cloud properties

Cornet¹,

Szczap²,

C.‐Labonnote³

et al. 2013

AIP Conference Proceedings

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Section: D Errors On Retrieved Cloud Optical Propertiessupporting

confidence: 74%

Evaluation of cloud heterogeneity effects on total and polarized visible radiances as measured by POLDER/PARASOL and consequences for retrieved cloud properties

Cornet¹,

Szczap²,

C.‐Labonnote³

et al. 2013

AIP Conference Proceedings

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“…Nakajima and King, 1990), measured radiances have been turned into science products, such as cloud optical depth and effective radius. If this approach is acceptable for a stratiform type clouds, it is suspect for clouds that are far from horizontally homogeneous (e.g., Varnai and Marshak, 2001;Iwabuchi and Hayasaka, 2002;Davis, 2002), especially for the clouds with a relatively small aspect ratio (the ratio of horizontal to vertical cloud dimensions) and well-developed cloud sides. These are the clouds the CLAIM-3D mission is directed for.…”

Section: Summary and Discussionmentioning

confidence: 99%

What does reflection from cloud sides tell us about vertical distribution of cloud droplet sizes?

et al. 2006

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Abstract. Cloud development, the onset of precipitation and the effect of aerosol on clouds depend on the structure of the cloud profiles of droplet size and phase. Aircraft measurements of cloud profiles are limited in their temporal and spatial extent. Satellites were used to observe cloud tops not cloud profiles with vertical profiles of precipitation-sized droplets anticipated from CloudSat. The recently proposed CLAIM-3D satellite mission (cloud aerosol interaction mission in 3-D) suggests to measure profiles of cloud microphysical properties by retrieving them from the solar and infrared radiation reflected or emitted from cloud sides.Inversion of measurements from the cloud sides requires rigorous understanding of the 3-dimentional (3-D) properties of clouds. Here we discuss the reflected sunlight from the cloud sides and top at two wavelengths: one nonabsorbing to solar radiation (0.67 µm) and one with liquid water efficient absorption of solar radiation (2.1 µm). In contrast to the plane-parallel approximation, a conventional approach to all current operational retrievals, 3-D radiative transfer is used for interpreting the observed reflectances. General properties of the radiation reflected from the sides of an isolated cloud are discussed. As a proof of concept, the paper shows a few examples of radiation reflected from cloud fields generated by a simple stochastic cloud model with the prescribed vertically resolved microphysics. To retrieve the information about droplet sizes, we propose to use the probability density function of the droplet size distribution and its first two moments instead of the assumption about fixed values of the droplet effective radius. The retrieval algorithm is based on the Bayesian theorem that combines prior information about cloud structure and microphysics with radiative transfer calculations.

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“…A greater correlation between τ than r e , retrieved with the different methods, was also observed by McBride et al (2011) for the two-wavelength and slope retrievals. For this liquid cloud case, factors contributing to differences in retrieved r e values include varying effects of vertical profiles in r e evaluated at different wavelengths (Platnick, 2000), horizontal cloud inhomogeneities (e.g., Iwabuchi and Hayasaka, 2002;Marshak et al, 2006), and undetected presence of ice crystals (Sun and Shine, 1994). Although transmitted radiation interacts with cloud particles throughout the vertical extent of a cloud, this interaction is not the same for radiance at all wavelengths.…”

Section: Comparison Of Retrieved τ and R E For The Liquid Cloud Casementioning

confidence: 99%

“…Clouds reduce the globally and annually averaged solar radiation absorbed at the surface by 53 W m −2 and produce a net cooling of 21 W m −2 (Allan, 2011). Cloud radiative effects are governed by optical thickness (τ ), cloud particle effective radius (r e ), and thermodynamic phase (φ) (see, for example, Key and Intrieri, 2000;Sun and Shine, 1995;Wiscombe et al, 1984). Droplet size and water phase influence single scattering and absorption, primarily in the nearinfrared (NIR) region (Slingo, 1990;Twomey and Bohren, 1980;Wiscombe et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

A spectral method for discriminating thermodynamic phase and retrieving cloud optical thickness and effective radius using transmitted solar radiance spectra

et al. 2015

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Abstract.A new retrieval scheme for cloud optical thickness, effective radius, and thermodynamic phase was developed for ground-based measurements of cloud shortwave solar spectral transmittance. Fifteen parameters were derived to quantify spectral variations in shortwave transmittance due to absorption and scattering of liquid water and ice clouds, manifested by shifts in spectral slopes, curvatures, maxima, and minima. To retrieve cloud optical thickness and effective particle radius, a weighted least square fit that matched the modeled parameters was applied. The measurements for this analysis were made with the ground-based Solar Spectral Flux Radiometer in Boulder, Colorado, between May 2012 and January 2013. We compared the cloud optical thickness and effective radius from the new retrieval to two other retrieval methods. By using multiple spectral features, we find a closer fit (with a root mean square difference over the entire spectra of 3.1 % for a liquid water cloud and 5.9 % for an ice cloud) between measured and modeled spectra compared to two other retrieval methods which diverge by a root mean square of up to 6.4 % for a liquid water cloud and 22.5 % for an ice cloud. The new retrieval introduced here has an average uncertainty in effective radius ( ± 1.2 µm) smaller by factor of at least 2.5 than two other methods when applied to an ice cloud.

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Effects of Cloud Horizontal Inhomogeneity on the Optical Thickness Retrieved from Moderate-Resolution Satellite Data

Cited by 89 publications

References 39 publications

Evaluation of cloud heterogeneity effects on total and polarized visible radiances as measured by POLDER/PARASOL and consequences for retrieved cloud properties

Evaluation of cloud heterogeneity effects on total and polarized visible radiances as measured by POLDER/PARASOL and consequences for retrieved cloud properties

What does reflection from cloud sides tell us about vertical distribution of cloud droplet sizes?

A spectral method for discriminating thermodynamic phase and retrieving cloud optical thickness and effective radius using transmitted solar radiance spectra

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