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Focus Area on Surface Radiation/Albedo Product Validation


Zhuosen Wang, University of Maryland/GSFC, USA
Dominique Carrer, Météo-France, France
Ian Grant, Bureau of Meteorology, Australia

 

Albedo Definition

Albedo is defined as the ratio of the radiant flux reflected from a unit surface area into the whole hemisphere to the incident radiant flux of hemispherical angular extent (Schaepman-Strub et al., 2006). It can be defined for broad spectral regions or for spectral bands of finite width. Albedo measures include black-sky albedo (or directional hemispherical reflectance, DHR) defined in the absence of a diffuse irradiance component (no atmospheric scattering), wholly diffuse white-sky albedo (or bihemispherical albedo, BHR, under isotropic illumination), and actual or blue-sky albedo (BHR under ambient conditions).

Units: Albedo is a non-dimensional quantity.


Highest Validation Stage Currently Reached for Satellite-Derived Albedo Products

Validation stage 3 (LPV validation stage hierarchy) - The highest LPV validation stage reached for satellite-derived albedo products. Limitations in reaching higher validation stage are due to the sparse spatial distribution of high-quality albedometers with representative footprints at satellite pixel scales, and missing aerosol optical depth measurements (sun photometer or satellite-derived) required to generate blue-sky albedo from satellite-derived black- and white-sky albedo products.


Validation Good Practice

The LPV Subgroup has just published a Best Practices Protocol document for validation of global albedo products. The document is available for download:

Wang, Z., Schaaf, C., Lattanzio, A., Carrer, D., Grant, I., Román, M., Camacho, F., Yu, Y., Sánchez-Zapero, J. &    Nickeson, J. (2019). Global Surface Albedo Product Validation Best Practices Protocol. Version 1.0. In Z. Wang, J.    Nickeson & M. Román (Eds.), Best Practice for Satellite Derived Land Product Validation (p. 45): Land Product    Validation Subgroup (WGCV/CEOS), doi: 10.5067/DOC/CEOSWGCV/LPV/ALBEDO.001

Download CEOS_ALBEDO_Protocol_20190307_v1.pdf (2MB)


Albedo Validation Reference Data Sets

Best currently available in situ reference data for satellite-derived albedo product validation are provided by in situ operational networks such as BSRN, Surfrad, and Fluxnet. At this point, these data sets are only available in their original formats. At a later stage the plan is to make a quality-screened data set of representative sites accessible through the OLIVE portal.

The validation of land surface albedo from geostationary satellites is currently being addressed within the Scope-CM project (see our Collaboration page). EUMETSAT Meteosat Surface Albedo (MSA) has been evaluated within the ALBEDOVAL-1 and ALBEDOVAL-2 projects, which utilized a set of Surface Albedo Validation Sites. At this EUMETSAT link you will find a map of site locations as well as a 'View Report' page where details about the sites can be found along with options for downloading the site database.


LPV Focus Areas

 

Meetings

EGU 2017, 23-28 April 2017, Vienna, Austria. Abstract submission due 11 Jan 2017, details here.

ESA Annouces first gathering of the Sentinel-2 Validation Team (S2VT), 8-29 November 2016, at ESRIN, Frascati, Italy.

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