Remote Sensing

Success Stories of Satellite Radar Altimeter Applications

For nearly three decades, satellite nadir altimeters have provided essential information to understand primarily ocean but also inland water dynamics. A variety of parameters can be inferred via altimeter measurements, including sea surface height, sea surface wind speeds, significant wave heights, and topography of land, sea ice, and ice sheets. Taking advantage of these parameters with the long record of altimeter data spanning multiple decades has allowed a diverse range of societal applications. In this paper, we review selected altimeter success stories that incorporate altimetry data, alone or in conjunction with numerical models or other Earth observations, to solve a key societal problem.


Timeline of the satellite radar altimetry missions since 1985.

• The growing constellation of altimeter satellites results in greater quantity (increasing record) and quality (increasing accuracy) of data and information products available to researchers and decision-makers.
• Development of altimeter-based datasets and the continued promotion of success stories at the global scale will support and highlight the potential societal applications of the forthcoming SWOT mission.

Scientific Focus Area (SFA): Remote Sensing

Reference: Eldardiry, H., Hossain, F., Srinivasan, M., & Tsontos, V. (2022). Success stories of satellite radar altimeter applications. Bulletin of the American Meteorological Society, 103(1), E33-E53. (DOI:

Satellite-based Framework for Modeling Reservoir Operation

This study presents the water management value of a modeling framework to predict the current and future reservoir operating rules in lower Nile basin using satellite earth observations and hydrologic models. The platform comprises the Variable Infiltration Capacity (VIC) hydrologic model driven by high spatial and temporal resolution of satellite observations. Reservoir storage change is estimated using altimeter and visible imagery of lake area for Lake Nasser and then applied to infer reservoir operation for High Aswan Dam (HAD).


Upper Panel: The discharge anomalies at Eldiem station (location of GERD dam in Ethiopia) averaged over the rainy season JJAS (June-July-August-September) during the period (1981–2017). Lower Panel: Operating curve of HAD for wet vs drought episodes using the satellite-based framework

• The hydrological modeling of the BNB shows high accuracy in simulating streamflow along the Blue Nile Basin (validated at Khartoum and Eldiem stations).
• Monthly HAD releases using satellite altimeter show good agreement with measured discharge downstream of the dam.

Scientific Focus Area (SFA): Integrated Modeling - Remote Sensing

Reference: Eldardiry, H., & Hossain, F. (2019). Understanding Reservoir Operating Rules in the Transboundary Nile River Basin Using Macroscale Hydrologic Modeling with Satellite Measurements. Journal of Hydrometeorology, 20(11), 2253-2269 (DOI:

Adapting High Aswan Dam Operation to Challenges of the Grand Ethiopian Renaissance Dam

The resilience of HAD operation to GERD construction typifies one of the challenges facing dam operators and water managers in downstream Nile riparian countries. Recently, various studies have investigated the impacts of GERD on downstream countries with more focus on the GERD filling strategies. However, crucial insights on how dam operators can adapt to potential impacts have not been capitalized in previous studies. Our study proposes a physical blueprint that employs water scarcity indices to infer modified reservoir operation that could adapt to streamflow alterations while maintaining the supply to downstream water use, i.e., water supply for irrigation and hydropower demands.


Schematic diagram of the blueprint proposed to re-evaluate the operation of existing dam under the filling/operation of an upstream planned dam.

• High Aswan Dam can adapt its operation in summer months by elevating the downstream stress level (store more and release less), to mitigate the effects of rapid GERD filling.
• A 7-year filling scenario by Ethiopia is minimally disruptive to operations of High Aswan Dam and results in faster recovery.

Scientific Focus Area (SFA): Integrated Modeling - Remote Sensing - Infrastructure Resilience

Reference: Eldardiry, H., & Hossain, F. (2020). A Blueprint for Adapting High Aswan Dam Operation in Egypt to Challenges of Filling and Operation of the Grand Ethiopian Renaissance Dam. Journal of Hydrology (DOI:

On the Use of Radar-based Quantitative Precipitation Estimates for Precipitation Frequency Analysis

This study investigated three fundamental issues that arise when radar-based QPE products are used in frequency analysis: (a) Effect of sample size due to the typically short records of radar products; (b) Effect of uncertainties present in radar-rainfall estimation algorithms; and (c) Effect of the frequency estimation approach adopted. We used a 13-year dataset of hourly, 4x4 km2 radar-based over a domain that covers Louisiana, USA.


Spatial Distribution of the Mean Annual Maxima (MAM) over Louisiana during the study period (2002-2014).

• The relatively short radar records explained the majority of the uncertainty associated with the radar-based quantiles.
• A systematic underestimation bias is observed between radar- and gauge-bases frequency estimates, which was mostly attributable to the conditional bias inherent in the radar product.

Scientific Focus Area (SFA): Extreme Events

Reference: Eldardiry, H., Habib, E., & Zhang, Y. (2015). On the use of radar-based quantitative precipitation estimates for precipitation frequency analysis. Journal of Hydrology, 531, 441-453 (DOI:

Artifacts in Stage IV NWS Real-time Multisensor Precipitation Estimates and Impacts on Identification of Maximum Series

This study focuses on data artifacts in the Stage IV radar-based Quantitative Precipitation Estimates (QPE) product over its full record period (2002-2013) and assesses their impacts on the analysis and derivation of heavy rainfall statistics. Examining annual maximum series extracted from the Stage IV 1-h accumulation product revealed the presence of numerous artifacts that were mostly linked to erroneous rain gauge reports and which can be mistaken as rainfall maxima.


First field of Partial Duration Series (PDS) of hourly precipitation (mm) over the CONUS for the period of study, 2002-2013 (maximum value at each individual pixel).

• Artifacts detected in Stage IV QPE had negative impacts on the estimation of parameters and quantiles of commonly-used extreme value probability distributions
• Stage IV 6-h and 24-h accumulations, as well as the longer-latency QPE archive from the regional River Forecasting Centers (RFCs), are mostly free from the artifacts shown in the Stage IV 1-h product.

Scientific Focus Area (SFA): Extreme Events

Reference: Eldardiry, H., Habib, E., Zhang, Y., & Graschel, J. (2015). Artifacts in Stage IV NWS real-time multisensor precipitation estimates and impacts on identification of maximum series. Journal of Hydrologic Engineering, 22(5), E4015003. (DOI: