IEEE Geoscience and Remote Sensing Magazine - March 2020 - 132

-50
-100
0

10
(Dist.: km)
(a)

-50
-100
0

30
0

10
(b)

10
0
-10
0
10

(cm/46 Days)

(cm)

500
400

30
0

(c)

10
(d)

FIGURE 10. (a) The modeled water-elevation maps on 16 April (lower half) and 1 June 2008 (upper half). (b) The modeled water-elevation-

change map. (c) The InSAR-based water-elevation-change map. (d) The difference between the modeled and InSAR-based water-elevation
change (from [75]).
is much shorter than the 35 d of the Envisat advanced SAR
and 24 d of Radarsat-1. The L-band SAR-system JERS-1 and
ALOS have revisiting periods of 44 and 46 d, respectively.
The revisiting periods of new L-band SAR missions are also
designed to be shortened. For instance, the currently operating ALOS-2 and Satélite Argentino de Observación Con Microondas have revisiting cycles of 14 and 16 d, respectively.
The NASA-Indian Space Research Organization SAR mission (to launch in 2021) will have a revisiting cycle of 12 d.
These new SAR systems are expected to have less temporal
decorrelation and a better ability to capture the temporal
dynamics of the wetland hydrology.
The Surface Water and Ocean Topography (SWOT) mission that will launch in 2021 has wide-swath altimetry that
uses a Ka-band radar interferometer to simultaneously measure the water surface's elevation and extent [81]. It promises to improve global surface-water monitoring [82]. It is
not clear how SWOT will work in vegetated wetlands, but
wetland monitoring can benefit from two of the mission's
characteristics. SWOT can measure vegetation submerged
beneath wetland water surfaces. This ability complements
the traditional SAR system, which does not work for submerged vegetation. Furthermore, the wide swath of the
SWOT can cover a much larger area compared to the current profile-based radar-altimetry missions. Thus, SWOT
can provide offset estimates in wetlands, as discussed in the
section "Relative Water-Level Changes."
INTEGRATION WITH HYDROLOGICAL MODELS
The role of riverine wetlands as a water buffer in the fluvial system is not well represented in the global river-routing model [83]. Yamazaki et al. [83] developed the catchment-based, macroscale-floodplain global river-routing
model by parameterizing the wetland topography to represent the riverine wetlands in storing and releasing water in a flat Amazon River area. The model demonstrated
132

superior river-discharge prediction. Thus, the improved
topography discussed in the "Forested-Wetlands Topography" section has the potential to help enhance model the
role wetlands play in buffering water in the fluvial system.
ACKNOWLEDGMENTS
This work was supported, in part, by NASA (grants 80NSSC18K0434 and 80NSSC20K0152) and the South Korea
Ministry of Environment's Demand Responsive Water Supply Service Program (grant 2019002650004). Some of the
Advanced Land Observation Satellite and Advanced Land Observation Satellite-2 images were provided by the Japan Aerospace Exploration Agency (PI number: 3069) and Alaska
Satellite Facility.
AUTHOR INFORMATION
Hyongki Lee (hlee@uh.edu) received his B.S. degree in

civil engineering and his M.S. degree in geomatics and surveying from Yonsei University, Seoul, Korea, in 2000 and
2002, respectively, and his Ph.D. degree in geodetic science
from The Ohio State University in 2008. He is an associate
professor with the Department of Civil and Environmental
Engineering, University of Houston.
Ting Yuan (tyuan3@ucla.edu) received her B.S. and M.S.
degrees in geomatics engineering from Wuhan University,
China, in 2009 and 2011, respectively, and her Ph.D. degree
in geosensing systems engineering and sciences from the
University of Houston, Texas, in 2017. She is with the Department of Geography, University of California, Los Angeles.
Hanwen Yu (hyu18@uh.edu) received his B.S. and
Ph.D. degrees in electronic engineering from Xidian University, Xi'an, China, in 2007 and 2012, respectively. He
received his M.S. degree in computer science from the University of Memphis, Tennessee, in 2015. He is currently a
postdoctoral research fellow with the Department of Civil
and Environmental Engineering, University of Houston.
IEEE GEOSCIENCE AND REMOTE SENSING MAGAZINE

MARCH 2020

IEEE Geoscience and Remote Sensing Magazine - March 2020

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