Spatio-temporal Error on the Discharge Estimates for the SWOT Mission
Abstract
The Surface Water and Ocean Topography (SWOT) mission measures two key quantities over rivers: water surface elevation and slope. Water surface elevation from SWOT will have a vertical accuracy, when averaged over approximately one square kilometer, on the order of centimeters. Over reaches from 1-10 km long, SWOT slope measurements will be accurate to microradians. Elevation (depth) and slope offer the potential to produce discharge as a derived quantity. Estimates of instantaneous and temporally integrated discharge from SWOT data will also contain a certain degree of error. Two primary sources of measurement error exist. The first is the temporal sub-sampling of water elevations. For example, SWOT will sample some locations twice in the 21-day repeat cycle. If these two overpasses occurred during flood stage, an estimate of monthly discharge based on these observations would be much higher than the true value. Likewise, if estimating maximum or minimum monthly discharge, in some cases, SWOT may miss those events completely. The second source of measurement error results from the instrument's capability to accurately measure the magnitude of the water surface elevation. How this error affects discharge estimates depends on errors in the model used to derive discharge from water surface elevation. We present a global distribution of estimated relative errors in mean annual discharge based on a power law relationship between stage and discharge. Additionally, relative errors in integrated and average instantaneous monthly discharge associated with temporal sub-sampling over the proposed orbital tracks are presented for several river basins.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H43G1106B
- Keywords:
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- 1855 Remote sensing (1640);
- 1860 Streamflow;
- 1872 Time series analysis (3270;
- 4277;
- 4475);
- 1894 Instruments and techniques: modeling