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A consistent record of vegetation optical depth retrieved from the AMSR-E and AMSR2 X-band observations
- Source :
- International Journal of Applied Earth Observation and Geoinformation, International Journal of Applied Earth Observation and Geoinformation, 2021, 105, pp.1-16. ⟨10.1016/j.jag.2021.102609⟩, International Journal of Applied Earth Observation and Geoinformation, Elsevier, 2021, 105, pp.1-16. ⟨10.1016/j.jag.2021.102609⟩
- Publication Year :
- 2021
- Publisher :
- HAL CCSD, 2021.
-
Abstract
- International audience; Vegetation optical depth (VOD) retrieved from microwave remote sensing techniques has been used as an important proxy for monitoring the vegetation dynamics at large scales. In a first study we developed a new X-VOD indice from inversion of the X-MEB model from the Microwave Scanning Radiometer 2 (AMSR2, 2012-present) observations. The Advanced Microwave Scanning Radiometer for EOS (AMSR-E, 2002–2011) and AMSR2 share many characteristics, such as local crossing time, incidence angle, frequency at X-band, etc, which makes it possible to produce a consistent long-term X-VOD product over a long period spanning from 2002 to present. The objective of this study was to merge the AMSR-E and AMSR2 observations in order, in a second step, to produce a consistent long-term X-VOD product spanning over the combined periods of AMSR-E and AMSR2.The main challenges in retrieving a consistent X-VOD data set from AMSR-E and AMSR2 are that (i) there is a bias between observations from the two sensors; and (ii) the lack of overlapping observations between the two sensors makes it impossible to achieve a direct inter-calibration. Here, to overcome this problem, we used AMSR-E slow rotation data (AMSR-E L1S), which has similar characteristics as AMSR-E and provided observations concurrently with AMSR2, as a bridge to calibrate the AMSR-E brightness temperature (TB) observations with AMSR2 TB.As our main objective in this TB calibration study was to produce a consistent long-term AMSR-E/AMSR2 X-VOD product, we evaluated the retrieved X-VOD product based on different inter-calibration, either global-based or pixel-based, methods. Both AMSR-E and AMSR2 X-VOD were evaluated against the Aboveground Biomass (AGB), Leaf Area Index (LAI) and the Normalized Difference Vegetation Index (NDVI). The results suggest that global-based inter-calibration methods using homogeneous and temporally stable land covers (Evergreen Broadleaf Forests and Snow and Ice) as reference calibration data sets provided the best results. For instance, the spatial relationships between X-VOD and AGB/LAI/NDVI are highly consistent over the AMSR-E and AMSR2 periods after the calibration work. This study laid a solid foundation for monitoring the dynamics of X-VOD, as a proxy of AGB, over the combined periods of AMSR-E and AMSR2 sensors (almost 20 years).
- Subjects :
- 010504 meteorology & atmospheric sciences
[SDV]Life Sciences [q-bio]
Management, Monitoring, Policy and Law
01 natural sciences
Normalized Difference Vegetation Index
03 medical and health sciences
Calibration
AGB
Vegetation optical depth
Computers in Earth Sciences
Leaf area index
Proxy (statistics)
030304 developmental biology
0105 earth and related environmental sciences
Earth-Surface Processes
Remote sensing
0303 health sciences
Global and Planetary Change
Radiometer
AMSR-E
15. Life on land
Snow
Data set
IB X-VOD
13. Climate action
Brightness temperature
Environmental science
AMSR2
Subjects
Details
- Language :
- English
- ISSN :
- 15698432, 1872826X, and 03032434
- Database :
- OpenAIRE
- Journal :
- International Journal of Applied Earth Observation and Geoinformation, International Journal of Applied Earth Observation and Geoinformation, 2021, 105, pp.1-16. ⟨10.1016/j.jag.2021.102609⟩, International Journal of Applied Earth Observation and Geoinformation, Elsevier, 2021, 105, pp.1-16. ⟨10.1016/j.jag.2021.102609⟩
- Accession number :
- edsair.doi.dedup.....99036d21c98bbf1fb182fd76cd02584f