Location: Hydrology and Remote Sensing LaboratoryTitle: Mapping climatological bare soil albedos over the contiguous United States using MODIS data
|TAO, H. - University Of Wuhan|
|LIANG, S. - University Of Maryland|
|PENG, Y. - Wuhan University|
Submitted to: Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2019
Publication Date: 3/19/2019
Citation: Tao, H., Gao, F.N., Liang, S., Peng, Y. 2019. Mapping climatological bare soil albedos over the contiguous United States using MODIS data. Remote Sensing. 11:666. https://doi.org/10.3390/rs11060666.
Interpretive Summary: Land surface albedo is the ratio of reflected radiation to the total incoming solar radiation. It is a key parameter used in climate modeling studies and remote sensing estimation of surface energy balance and water use. The total surface albedo is composed by albedos from bare soil and vegetation canopy. Currently, the soil albedo map is only available at 5-km resolution, which is too coarse for agricultural applications. This paper presents a new soil albedo dataset at 500-m resolution over the conterminous United States (CONUS) using multi-year Moderate Resolution Imaging Spectroradiometer (MODIS) data products. Relationships between bare soil albedo and other surface properties, such as soil moisture, soil type, and vegetation type, were explored. A better description of surface soil albedo can reduce the uncertainty in estimating crop water use, which is critical for developing sustainable agricultural systems for USDA.
Technical Abstract: Surface bare soil albedo is an important variable in climate modeling studies and satellite-based retrievals of land-surface properties. In this study, we used multiyear 500 m albedo products from the Moderate Resolution Imaging Spectroradiometer (MODIS) to derive the bare soil albedo for seven spectral bands and three broadbands over the contiguous United States (CONUS). The soil line based on red and green spectral signatures derived from MODIS data was used as the basis to detect and extract bare soil albedo. Comparison against bare soil albedo derived from 30 m Landsat data has been made, showing that the MODIS bare soil albedo had a bias of 0.003 and a root-mean-square-error (RMSE) of 0.036. We found that the bare soil albedo was negatively correlated with soil moisture from the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E), with a relatively stable exponential relationship reflecting the darkening effect that moisture has on most soils. However, quantification of the relationship between bare soil albedo and soil moisture still needs to be improved through simultaneous and instantaneous measurements at a finer spatial resolution. Statistics of the multiyear climatological bare soil albedos calculated using soil types and International Geosphere-Biosphere Programme (IGBP) land cover types suggest that: land cover type is a better indicator for determining the magnitude of bare soil albedos for the vegetated areas, as the vegetation density is correlated with soil moisture; and soil type is a better indicator for determining the slope of soil lines over sparsely vegetated areas, as it contains information of the soil texture, roughness, and composition. The generated bare soil albedo can be applied to improve the parameterization of surface energy budget in climate and remote sensing models, and the retrieval accuracy of some satellite products.