Satellite Remote Sensing of Inundated Wetlands: Data Record Assembly and Cross-Product Comparison

Abstract:

Wetlands cover less than 5% of Earth’s ice-free land surface but exert major impacts on global biogeochemistry, hydrology, and biological diversity. Despite the importance of these environments in the global cycling of carbon and water, there is a scarcity of suitable regional-to-global remote-sensing data for characterizing their distribution and dynamics. We have been assembling a global-scale Earth System Data Record (ESDR) of natural Inundated Wetlands to facilitate investigations on their role in climate, biogeochemistry, hydrology, and biodiversity. The ESDR comprises (1) Fine-resolution (100 meter) maps, delineating wetland extent, vegetation type, and seasonal inundation dynamics for regional to continental-scale areas covering crucial wetland regions, and (2) global coarse-resolution (~25 km), multi-temporal mappings of inundated area fraction (F_w) across multiple years. The fine-scale ESDR component is constructed from L-band synthetic aperture radar (SAR) data. The global maps of inundated area fraction are obtained by combining coarse-resolution (~25 km) remote sensing observations from passive and active microwave instruments.

Surface water and inundated vegetation is classified at 100m resolution using ALOS PALSAR imagery. We combine multiple passive/active microwave data sets to quantify F_wat 25 km resolution producing a daily product with ~weekly temporal composites from 1992-2013. We compare information content and accuracy of the coarse resolution data sets relative to the SAR-based data sets. This ESDR will provide the first high-resolution, accurate, consistent and comprehensive global-scale data set of wetland inundation and vegetation. We present details of assembly of this ESDR, discussing aspects of remote sensing data collections, data processing and staging, algorithm application and adaptation to contemporary data streams, cross-product harmonization, and considerations for distribution with the user community.

This work was carried out in part within the framework of the ALOS Kyoto & Carbon Initiative. PALSAR data were provided by JAXA/EORC and the Alaska Satellite Facility. Portions of this work were conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract to the National Aeronautics and Space Administration.