Characterizing Open Water Bodies and Wetland Ecosystems Using Optical and Microwave Remote Sensing

Abstract:

Inundated vegetation and open water bodies are common features across the landscape and exert major impacts on hydrologic processes and surface-atmosphere carbon exchange. Their carbon emissions can have a large impact on global climate. It is therefore of great importance to assess their spatial extent and temporal variations in order to improve upon carbon balance estimates. Despite their importance in the global cycling of carbon and water and climate forecasting, they remain poorly characterized and modeled, primarily because of the scarcity of suitable regional-to-global remote sensing data for characterizing wetlands distribution and dynamics. Spaceborne microwave sensors are an effective tool for characterizing these ecosystems since they are sensitive to surface water and vegetation structure, and they can monitor large areas on a temporal basis regardless of atmospheric conditions or solar illumination. Optical sensors however provide much higher spatial resolution as well as information on water color.

We developed a methodology using data from the Advanced Land Observing Satellite (ALOS) Phased Array L-Band Synthetic Aperture Radar (PALSAR) to map wetland ecosystems at 100 meter resolution for target regions as well as SMAP radar data at 1 km resolution. We also used optical data from Landsat to map open water bodies and their color properties at 15 meter resolution. Inundation dynamics of these ecosystems was assessed using a coarser resolution, 25 km microwave product on surface water fraction, which was derived using combined active and passive microwave data from QuikSCAT and AMSR-E on a weekly basis. We compare information content and accuracy of the coarse resolution products to the PALSAR, SMAP and Landsat based datasets to ensure information harmonization. The combination of high and low resolution datasets will allow for characterization of wetlands and open water bodies and assessment of their flooding status.

This work has been undertaken partly within the framework of the JAXA ALOS Kyoto & Carbon Initiative. PALSAR data have been provided by JAXA/EORC. Portions of this work were carried out at City University of New York and JPL, Caltech, under contract with NASA.