Surface variability effects on the remote sensing of thin cirrus optical and microphysical properties

Rolland, P.; Liou, Kuo‐Nan

doi:10.1029/2001jd900160

Cited by 17 publications

(20 citation statements)

References 20 publications

(11 reference statements)

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“…Additional uncertainties may arise from inappropriate assumptions of surface albedo and ice crystal habit in the case of ice or mixed-phase clouds. According to Rolland and Liou (2001), Fricke et al (2014), and Ehrlich et al (2017), an inaccurate assumption of surface albedo can lead to uncertainties of up to 83 % for τ and 62 % for r eff . Eichler et al (2009) demonstrated that uncertainties of up to 70 % for τ and 20 % for r eff are obtained when an inappropriate ice crystal habit is assumed in cirrus retrievals.…”

Section: Introductionmentioning

confidence: 99%

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

et al. 2018

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Abstract. Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German High Altitude and Long Range Research Aircraft (HALO) during the Mid-Latitude Cirrus (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interaction and Dynamic of Convective Clouds System -Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modelling and to the Global Precipitation Measurement (ACRIDICON-CHUVA) campaigns. On particular flights, HALO performed measurements closely collocated with overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite. A cirrus cloud located above liquid water clouds and a DCC topped by an anvil cirrus are analyzed in this paper. Based on the nadir spectral upward radiance measured above the two clouds, the optical thickness τ and particle effective radius r eff of the cirrus and DCC are retrieved using a radiance ratio technique, which considers the cloud thermodynamic phase, the vertical profile of cloud microphysical properties, the presence of multilayer clouds, and the heterogeneity of the surface albedo. For the cirrus case, the comparison of τ and r eff retrieved on the basis of SMART and MODIS measurements yields a normalized mean absolute deviation of up to 1.2 % for τ and 2.1 % for r eff . For the DCC case, deviations of up to 3.6 % for τ and 6.2 % for r eff are obtained. The larger deviations in the DCC case are mainly attributed to the fast cloud evolution and three-dimensional (3-D) radiative effects. Measurements of spectral upward radiance at near-infrared wavelengths are employed to investigate the vertical profile of r eff in the cirrus. The retrieved values of r eff are compared with corresponding in situ measurements using a vertical weighting method. Compared to the MODIS observations, measurements of SMART provide more information on the vertical distribution of particle sizes, which allow reconstructing the profile of r eff close to the cloud top. The comparison between retrieved and in situ r eff yields a normalized mean absolute deviation, which ranges between 1.5 and 10.3 %, and a robust correlation coefficient of 0.82.

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Section: Introductionmentioning

confidence: 99%

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

et al. 2018

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“…The accuracy of the surface albedo assumed in the forward simulations influences the uncertainty of the retrieved cloud properties (Rolland and Liou, 2001;Fricke et al, 2014;. For vertically homogenous clouds, these studies found uncertainties of up to 83 % and 62 % in the retrieved values of τ and r eff , respectively, when an inaccurate surface albedo is assumed in the forward simulation.…”

Section: Heterogeneity Of the Surface Albedomentioning

confidence: 93%

Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique

Krisna

Wendisch

Ehrlich

et al. 2017

Preprint

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Abstract. Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German HALO (High Altitude and Long Range Research Aircraft) during the ML-CIRRUS and the ACRIDICON-CHUVA campaigns. In particular flights, HALO performed closely collocated measurements with overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) on board of Aqua satellite. Based on the nadir upward radiance, the optical thickness τ and bulk particle effective radius r eff of cirrus and DCC 5 are retrieved using a radiance ratio algorithm which considers the cloud thermodynamic phase, the cloud vertical profile, multi layer clouds, and heterogeneity of the surface albedo. For the cirrus case, the comparison of τ ci and r eff,ci retrieved on the basis of SMART and MODIS upward radiances yields a normalized mean absolute deviation of 0.5 % for τ ci and 2.5 % for r eff,ci . While for the DCC case, the respective deviation is 5.9 % for τ dcc and 13.2 % for r eff,dcc . The larger deviations in case of DCC are mainly attributed to the fast cloud evolution and three-dimensional radiative effects. Measurements of spectral 10 radiance at near-infrared wavelengths with different absorption by cloud particles are employed to investigate the vertical profile of cirrus effective radius. The retrieved values of cirrus effective radius are further compared with corresponding in situ measurements using a vertical weighting method. Compared to the MODIS observation, spectral measurements of SMART provide an increased amount of information on the vertical distribution of particle sizes at cloud top, and therefore allow to reconstruct the profile of effective radius at cloud top. The retrieved effective radius differs to in situ measurements with 15 a normalized mean absolute deviation between 4 − 19 %, depending on the wavelength chosen in the retrieval algorithm.While, the MODIS cloud product underestimates the in situ measurements by 48 %. The presence of liquid water clouds below Atmos. Chem. Phys. Discuss., https://doi

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“…[1][2][3] It is known that the probability of photon absorption, ␤ =1− ͑where is the singlescattering albedo͒, by a local cloud volume in the visible and near infrared depends primarily on the product of the water or ice absorption coefficient ␣ =4 / and the effective radius of particles, a ef . 4,5 Here is the wavelength, is the imaginary part of the refractive index of water or ice, and a ef =3 / s, where is the average volume of the particles and s is the their average surface area.…”

Section: Introductionmentioning

confidence: 99%

On remote sensing of optically thick ice clouds

Kokhanovsky¹

2006

Opt. Eng

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The author introduces new parameters for ice-cloud retrieval: the reduced optical depth and the particle absorption length. The retrieval of these parameters from backscattering solar light measurements depends only weakly on the assumption on the habits of particles made in retrieval procedures. This allows one to avoid major difficulties in modern ice-cloud retrieval algorithms related to a priori assumptions on the shape of crystals in ice clouds. © 2006 Society of Photo-Optical Instrumentation Engineers.

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Surface variability effects on the remote sensing of thin cirrus optical and microphysical properties

Cited by 17 publications

References 20 publications

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique

On remote sensing of optically thick ice clouds

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