Assembly and Assessment of a Global-scale Earth Science Data Record of Inundated Wetlands supporting Hydrology Applications

Wetlands exert major impacts on biogeochemistry, hydrology, and biological diversity at local, regional and global scales. The extent and seasonal, interannual, and decadal variation of inundated wetland areas play key roles in ecosystem dynamics. Despite the importance of these environments in hydrologic processes, the global cycling of carbon and water, and to current and future climate, the extent and dynamics of global wetlands remain poorly characterized and modeled, primarily because of the scarcity of suitable regional-to-global remote-sensing data for characterizing their distribution and dynamics. We present details on the construction and assessment of a global-scale Earth System Data Record (ESDR) of inundated wetlands to facilitate investigations on their role in hydrology, climate, biogeochemistry, 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 (Fw) across multiple years at high temporal fidelity (daily to weekly). 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. We present details of ESDR construction including remote sensing algorithm application, cross-product harmonization, and dataset assessment. We employ a unique dataset collected by UAVSAR, NASA's airborne Synthetic Aperture Radar (SAR), during March and April 2013 in regions of inundated forest in Ecuador and Peru. We compare inundation estimates derived from these polarimetric and interferometric L-band SAR data over inundated tropical forest with on-the-ground field measurements ascertaining the extent of inundation, and then derive from these data a quantitative estimate for the error in the SAR-derived inundation extent.

This ESDR will provide the first accurate, consistent and comprehensive global-scale data set of wetland inundation and vegetation, including continental-scale multitemporal and multi-year monthly inundation dynamics at multiple scales.

Funding and support for this work was provided by the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) program 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. This study was supported and monitored by the National Oceanic and Atmospheric Administration (NOAA) under Grant - CREST Grant # NA11SEC4810004.The statements contained within the manuscript/research article are not the opinions of the funding agency or the U.S. government, but reflect the author's opinions. Portions of this work were conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract to the National Aeronautics and Space Administration.