National Aeronautics and Space Administration (NASA)
Location
Pasadena, CA | United States
Job description
Description
The observation of rivers from space has benefitted from over 25 consecutive years of nadir altimetry observations. Past satellite missions include joint NASA and CNES (the French space agency) efforts such as TOPEX/Poseidon (1992-2006) (Fu et al., 1994) and its sister missions Jason-1 (2001-2013) (Ménard et al., 2003), Jason 2 (2008-current) (Lambin et al., 2010), and Jason-3 (2016-current) (Dumont et al., 2016). The separate series of nadir altimetry missions from the European Space Agency (ESA) consisting of ERS-1 (1991-2000), ERS-2 (1995-2011), EnviSat (2002-2012), and Sentinel-3 (2016-current) have similarly contributed to the observation of terrestrial hydrologic features (Donlon et al., 2012). Interestingly, all of these missions were initially designed to observe ocean topography, not rivers and lakes. However, because of its technological capabilities, nadir altimetry has also allowed for the estimation of water heights in continental hydrologic features when the satellites ground tracks intersect with the largest rivers. Such locations are often referred to as virtual gauges and measured water heights have traditionally been used with stage-discharge relationships to estimate river flow. Note that these virtual gauges of rivers and lakes have all been merely by-products of oceanography missions. The Surface Water and Ocean Topography (SWOT) mission (Alsdorf et al., 2007; Biancamaria et al., 2016), currently scheduled for launch in April 2021, is a joint pathfinder effort between the oceanography and hydrology communities, and is expected to observe unprecedented two-dimensional images of the location and height of terrestrial water bodies with a large increase in spatial resolution and in temporal frequency, a clear step forward compared to existing nadir altimetry missions. However, recent research has revealed limitations in our ability to compute accurate spatial and temporal averages in river height and discharge from the traditional NASA Level 2 remote sensing data products that provide hydrologic estimates only at times and locations of the satellite measurements. This limitation not only applies to the expected measurements of SWOT, it also inhibits the utility of past nadir altimetry data. We have also developed a suite of relevant capabilities - e.g. high-performance river models with uncertainty quantification - for the creation of new algorithms using data assimilation (Level 4) and in doing so, we have demonstrated a positive impact on data product quality. Here we encourage applicants to NASA’s Postdoctoral Program to propose innovative research ideas to advance three major connected research efforts: 1) the development of new Level 4 algorithms using data assimilation to fill in the blanks in space and in time between remotely sensed estimates of surface water while decreasing uncertainty, 2) the global application of such new algorithms to existing and upcoming space-based estimates of surface water height and flow, and 3) the quantification of the value of such Level 4 algorithms with respect to the traditional Level 2 algorithms that only provide hydrologic estimates at the times and locations of remote sensing retrievals. Note that we promote the use and development of NASA’s existing software, including the RAPID river routing model (David et al., 2011, 2016) ( and its associated pre/post-processing toolbox (). The successful NPP candidate(s) will work together with Dr. Cédric H. David and other members of JPL’s Terrestrial Hydrology group to develop new capabilities resulting in publications in the open literature.
References:
Alsdorf, D. E., Rodriguez, E., & Lettenmaier, D. P. (2007). Measuring surface water from space. Reviews of Geophysics, 45(2). Biancamaria, S., Lettenmaier, D. P., & Pavelsky, T. M. (2016). The SWOT Mission and Its Capabilities for Land Hydrology. Surveys in Geophysics, 37(2), 307–337. David, C. H., Maidment, D. R., Niu, G.-Y., Yang, Z.-L., Habets, F., & Eijkhout, V. (2011). River Network Routing on the NHDPlus Dataset. Journal of Hydrometeorology, 12(5), 913–934. David, C. H., Famiglietti, J. S., Yang, Z.-L., Habets, F., & Maidment, D. R. (2016). A decade of RAPID—Reflections on the development of an open source geoscience code. Earth and Space Science, 3(5), 226–244. Donlon, C., Berruti, B., Buongiorno, A., Ferreira, M.-H., Féménias, P., Frerick, J., … Sciarra, R. (2012). The Global Monitoring for Environment and Security (GMES) Sentinel-3 mission. Remote Sensing of Environment, 120, 37–57. Dumont, Rosmorduc, V., Carrere, L., Picot, N., Bronner, E., Couhert, A., … Lillibridge, J. (2016). Jason-3 Products Handbook. CNES, EUMETSAT, JPL, NOAA/NESDIS. Retrieved from Fu, L.-L., Christensen, E. J., Yamarone, C. A., Lefebvre, M., Ménard, Y., Dorrer, M., & Escudier, P. (1994). TOPEX/POSEIDON mission overview. Journal of Geophysical Research: Oceans, 99(C12), 24369–24381. Lambin, J., Morrow, R., Fu, L.-L., Willis, J. K., Bonekamp, H., Lillibridge, J., … Mignogno, M. (2010). The OSTM/Jason-2 Mission. Marine Geodesy, 33(sup1), 4–25. Ménard, Y., Fu, L.-L., Escudier, P., Parisot, F., Perbos, J., Vincent, P., … Kunstmann, G. (2003). The Jason-1 Mission Special Issue: Jason-1 Calibration/Validation. Marine Geodesy, 26(3–4), 131–146.
Location:Applications with citizens from Designated Countries will not be accepted at this time, unless they are Legal Permanent Residents of the United States. A complete list of Designated Countries can be found at: .
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