Validation of Moderate Resolution Imaging Spectroradiometer (MODIS) albedo retrieval algorithm: Dependence of albedo on solar zenith angle

Liu, Jicheng; Schaaf, Crystal B.; Strahler, Alan H.; Jiao, Ziti; Shuai, Yanmin; Zhang, Qingling; Román, M. O.; Augustine, John; Dutton, Ellsworth G

doi:10.1029/2008jd009969

Cited by 186 publications

(176 citation statements)

References 27 publications

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“…Errors arise from the MODIS retrievals themselves and the inference from these of values appropriate to the ATSR scene and spectral response. The assumed 0.2 fractional error and 0.4 correlation values are broadly consistent with the accuracy reported in (Liu et al, 2009). Further consideration of the use of MODIS albedo data in the ORAC scheme is given in (Sayer et al, 2011b).…”

Section: Measurement Vector and Covariancesupporting

confidence: 62%

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

Poulsen

Siddans

Thomas³

et al. 2012

Atmos. Meas. Tech.

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Abstract. Clouds play an important role in balancing the Earth's radiation budget. Hence, it is vital that cloud climatologies are produced that quantify cloud macro and micro physical parameters and the associated uncertainty. In this paper, we present an algorithm ORAC (Oxford-RAL retrieval of Aerosol and Cloud) which is based on fitting a physically consistent cloud model to satellite observations simultaneously from the visible to the mid-infrared, thereby ensuring that the resulting cloud properties provide both a good representation of the short-wave and long-wave radiative effects of the observed cloud. The advantages of the optimal estimation method are that it enables rigorous error propagation and the inclusion of all measurements and any a priori information and associated errors in a rigorous mathematical framework. The algorithm provides a measure of the consistency between retrieval representation of cloud and satellite radiances. The cloud parameters retrieved are the cloud top pressure, cloud optical depth, cloud effective radius, cloud fraction and cloud phase.The algorithm can be applied to most visible/infrared satellite instruments. In this paper, we demonstrate the applicability to the Along-Track Scanning Radiometers ATSR-2 and AATSR. Examples of applying the algorithm to ATSR-2 flight data are presented and the sensitivity of the retrievals assessed, in particular the algorithm is evaluated for a number of simulated single-layer and multi-layer conditions. The algorithm was found to perform well for single-layer cloud except when the cloud was very thin; i.e., less than 1 optical depths. For the multi-layer cloud, the algorithm was robust except when the upper ice cloud layer is less than five optical depths. In these cases the retrieved cloud top pressure and cloud effective radius become a weighted average of the 2 layers. The sum of optical depth of multi-layer cloud is retrieved well until the cloud becomes thick, greater than 50 optical depths, where the cloud begins to saturate. The cost proved a good indicator of multi-layer scenarios. Both the retrieval cost and the error need to be considered together in order to evaluate the quality of the retrieval. This algorithm in the configuration described here has been applied to both ATSR-2 and AATSR visible and infrared measurements in the context of the GRAPE (Global Retrieval and cloud Product Evaluation) project to produce a 14 yr consistent record for climate research.

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Section: Measurement Vector and Covariancesupporting

confidence: 62%

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

Poulsen

Siddans

Thomas³

et al. 2012

Atmos. Meas. Tech.

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“…To match this data perfectly to the CLARA-SAL black-sky albedo, we would need to remove all diffuse flux contributions (resulting from atmospheric scattering), and also account for any possible absorption effects in the direct flux. However, Liu et al (2009) showed in their study that the difference between black-sky and blue-sky albedo is very small in cloudfree conditions when SZA is less than 70 degrees. Manninen et al (2012) showed that the difference between black-sky and blue-sky albedo measurements on the ground at Cabauw in the Netherlands is typically no more than 5 %, although the difference increases with increasing AOD.…”

Section: Validation Against Ground Truthmentioning

confidence: 99%

CLARA-SAL: a global 28 yr timeseries of Earth's black-sky surface albedo

et al. 2013

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We present a novel 28 yr dataset of Earth's black-sky surface albedo, derived from AVHRR instruments. The dataset is created using algorithms to separately derive the surface albedo for different land use areas globally. Snow, sea ice, open water and vegetation are all treated independently. The product features corrections for the atmospheric effect in satellite-observed surface radiances, a BRDF correction for the anisotropic reflectance properties of natural surfaces, and a novel topography correction of geolocation and radiometric accuracy of surface reflectance observations over mountainous areas. The dataset is based on a homogenized AVHRR radiance timeseries. The product is validated against quality-controlled in situ observations of clear-sky surface albedo at various BSRN sites around the world. Snow and ice albedo retrieval validation is given particular attention using BSRN sites over Antarctica, Greenland Climate Network stations on the Greenland Ice Sheet (GrIS), as well as sea ice albedo data from the SHEBA and Tara expeditions. The product quality is found to be comparable to other previous long-term surface albedo datasets from AVHRR

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“…While MODIS albedo products at local solar noon are used in the previous section albedo evaluation, MODIS BRDF/albedo parameters retrieved are more appropriate for WRF/CMAQ simulations with changing solar zenith angle (SZA, θ Sun ). The MODIS product can be used to characterize the actual albedo at a location throughout the better part of the diurnal cycle with some confidence based on the study by Liu et al [2009]. Although many surface conditions (such as soil conditions, canopy, surface heterogeneity, and spatial scale) affect surface albedo; direct-beam albedo may be predominately influenced by SZA [Yang et al, 2008].…”

Section: Modis Datamentioning

confidence: 99%

Sensitivity of the Weather Research and Forecast/Community Multiscale Air Quality modeling system to MODIS LAI, FPAR, and albedo

et al. 2015

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This study aims to improve land surface processes in a retrospective meteorology and air quality modeling system through the use of Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation and albedo products for more realistic vegetation and surface representation. MODIS leaf area index (LAI), fraction of absorbed photosynthetically active radiation (FPAR), and albedo are incorporated into the Pleim-Xiu land surface model (PX LSM) used in a combined meteorology and air quality modeling system. The current PX LSM intentionally exaggerates vegetation coverage and LAI in western dry lands so that its soil moisture nudging scheme is more effective in simulating surface temperature and mixing ratio. Reduced vegetation coverage from the PX LSM with MODIS input results in hotter and dryer daytime conditions with reduced ozone dry deposition velocities in much of western North America. Evaluations of the new system indicate greater error and bias in temperature, but reduced error and bias in moisture with the MODIS vegetation input. Hotter daytime temperatures and reduced dry deposition result in greater ozone concentrations in the western arid regions even with deeper boundary layer depths. MODIS albedo has much less impact on the meteorology simulations than MODIS LAI and FPAR. The MODIS vegetation and albedo input does not have much influence in the east where differences in vegetation and albedo parameters are less extreme. Evaluation results showing increased temperature errors with more accurate representation of vegetation suggests that improvements are needed in the model surface physics, particularly the soil processes in the PX LSM.

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Validation of Moderate Resolution Imaging Spectroradiometer (MODIS) albedo retrieval algorithm: Dependence of albedo on solar zenith angle

Cited by 186 publications

References 27 publications

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

CLARA-SAL: a global 28 yr timeseries of Earth's black-sky surface albedo

Sensitivity of the Weather Research and Forecast/Community Multiscale Air Quality modeling system to MODIS LAI, FPAR, and albedo

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