Bacour, C;
Bréon, FM;
Gonzalez, L;
Price, I;
Muller, JP;
Prunet, P;
Straume, AG;
(2020)
Simulating multi-directional narrowband reflectance of the earth's surface using ADAM (a surface reflectance database for ESA's earth observation missions).
Remote Sensing
, 12
(10)
, Article 1679. 10.3390/rs12101679.
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Abstract
The ADAM (A Surface Reflectance Database for ESA's Earth Observation Missions) product (a climatological database coupled to its companion calculation toolkit) enables users to simulate realistic hyperspectral and directional global Earth surface reflectances (i.e., top-of-canopy/bottom-of-atmosphere) over the 240-4000 nm spectral range (at 1-nm resolution) and in any illumination/observation geometry, at 0.1° x 0.1° spatial resolution for a typical year. ADAM aims to support the preparation of optical Earth observation missions as well as the design of operational processing chains for the retrieval of atmospheric parameters by characterizing the expected surface reflectance, accounting for its anisotropy. Firstly, we describe (1) the methods used in the development of the gridded monthly ADAM climatologies (over land surfaces: monthly means of normalized reflectances derived from MODIS observations in seven spectral bands for the year 2005; over oceans: monthly means over the 1999-2009 period of chlorophyll content from SeaWiFS and of wind speed from SeaWinds), and (2) the underlying modeling approaches of ADAM toolkit to simulate the spectro-directional variations of the reflectance depending on the assigned surface type. Secondly, we evaluate ADAM simulation performances over land surfaces. A comparison against POLDER multi-spectral/multi-directional measurements for year 2008 shows reliable simulation results with root mean square differences below 0.027 and R2 values above 0.9 for most of the 14 land cover IGBP classes investigated, with no significant bias identified. Only for the "Snow and ice" class is the performance lower pointing to a limitation of climatological data to represent actual snow properties. An evaluation of the modeled reflectance in the specific backscatter direction against CALIPSO data reveals that ADAM tends to overestimate (underestimate) the so-called "hot-spot" by a factor of about 1.5 (1.5 to 2) for barren (vegetated) surfaces.
| Type: | Article |
|---|---|
| Title: | Simulating multi-directional narrowband reflectance of the earth's surface using ADAM (a surface reflectance database for ESA's earth observation missions) |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3390/rs12101679 |
| Publisher version: | https://doi.org/10.3390/rs12101679 |
| Language: | English |
| Additional information: | This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. - With correction dated 16 July 2020. |
| Keywords: | Hyperspectral reflectance; bidirectional reflectance distribution function (BRDF); climatology database; land and ocean surfaces; MODIS; SeaWinds; SeaWiFs |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10100379 |
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