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RESEARCH PRODUCT

Comparison between SMOS Vegetation Optical Depth products and MODIS vegetation indices over crop zones of the USA

Olivier MerlinSimone BircherDelphine LerouxArnaud MialonYann KerrPhilippe RichaumeAhmad Al BitarJean-pierre WigneronHeather LawrenceNathalie NovelloJennifer GrantDominique Guyon

subject

2. Zero hunger010504 meteorology & atmospheric sciences0211 other engineering and technologiesSoil ScienceGrowing seasonGeology02 engineering and technologyVegetationEnhanced vegetation index01 natural sciencesNormalized Difference Vegetation Indexvegetation optical depthLinear regressionEnvironmental scienceL-band radiometryModerate-resolution imaging spectroradiometerComputers in Earth SciencesLeaf area indexoptical vegetation indices[SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processingWater contentSMOS021101 geological & geomatics engineering0105 earth and related environmental sciencesRemote sensing

description

The Soil Moisture and Ocean Salinity (SMOS) mission provides multi-angular, dual-polarised brightness temperatures at 1.4 GHz, from which global soil moisture and vegetation optical depth (tau) products are retrieved. This paper presents a study of SMOS' tau product in 2010 and 2011 for crop zones of the USA. Retrieved tau values for 504 crop nodes were compared to optical/IR vegetation indices from the MODES (Moderate Resolution Imaging Spectroradiometer) satellite sensor, including the Normalised Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVE), Leaf Area Index (LAI), and a Normalised Difference Water Index (NOW!) product. tau values were observed to increase during the growing season and decrease during senescence in these areas, as did MODIS vegetation indices. SMOS' tau values generally peaked later than MODES LAI values, with an estimated time difference of about 19 days. A linear regression between tau and the MODIS products was carried out for each node and values of the determination coefficient, R-2, slope, b' and intercept, b '' were found. The average R-2 value varied from 0.32 to 035 for the different vegetation indices. The linear regression between LAI and tau produced an average slope of b' = 0.06, and an average intercept of b '' = 0.14. The effects of crop fraction and dominant crop type were investigated and crop fraction was found to have a low effect on R-2 values. R-2 values appeared to be lower for wheat and hay and higher for corn. b' and b '' values had higher standard deviations for wheat but were generally close to the mean values for corn, soybean and hay. (C) 2013 Published by Elsevier Inc. (Less)

yearjournalcountryeditionlanguage
2014-01-01Remote Sensing of Environment
https://doi.org/10.1016/j.rse.2013.07.021