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

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• 作者：Heather Lawrence ; Jean-Pierre Wigneron ; Philippe Richaume ; Nathalie Novello ; Jennifer Grant ; Arnaud Mialon ; Ahmad Al Bitar ; Olivier Merlin ; Dominique Guyon ; Delphine Leroux ; Simone Bircher ; Yann Kerr
• 关键词：SMOS ; Vegetation optical depth ; L-band radiometry ; Optical vegetation indices
• 刊名：Remote Sensing of Environment
• 出版年：January, 2014
• 年：2014
• 卷：140
• 期：Complete
• 页码：396-406
• 全文大小：2441 K

文摘

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 (蟿) products are retrieved. This paper presents a study of SMOS' 蟿 product in 2010 and 2011 for crop zones of the USA. Retrieved 蟿 values for 504 crop nodes were compared to optical/IR vegetation indices from the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite sensor, including the Normalised Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Leaf Area Index (LAI), and a Normalised Difference Water Index (NDWI) product. 蟿 values were observed to increase during the growing season and decrease during senescence in these areas, as did MODIS vegetation indices. SMOS' 蟿 values generally peaked later than MODIS LAI values, with an estimated time difference of about 19 days. A linear regression between 蟿 and the MODIS products was carried out for each node and values of the determination coefficient, R², slope, b鈥?and intercept, b鈥?were found. The average R² value varied from 0.32 to 0.35 for the different vegetation indices. The linear regression between LAI and 蟿 produced an average slope of b鈥?#xA0;= 0.06, and an average intercept of b鈥?#xA0;= 0.14. The effects of crop fraction and dominant crop type were investigated and crop fraction was found to have a low effect on R² values. R²values appeared to be lower for wheat and hay and higher for corn. b鈥?and b鈥?values had higher standard deviations for wheat but were generally close to the mean values for corn, soybean and hay.