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SDWBA

Source: vignettes/sdwba/index.Rmd
index.Rmd

Overview

Benchmarked Validated
Theory Implementation

These pages connect krill-body DWBA models to phase variability, orientation effects, and practical survey use (Demer and Stephane G. Conti 2003; Demer and Stéphane G. Conti 2003, 2005; Conti and Demer 2006).

The stochastic distorted wave Born approximation (SDWBA) extends the deterministic DWBA by treating unresolved posture and shape variability as stochastic phase variability along the body.

Core idea

Start from the same segmented weak-scattering sum as DWBA, then replace the strictly coherent phase accumulation by a randomized phase model whose statistics are chosen to mimic unresolved biological variability.

Best for

  • Krill-like or zooplankton-like targets where deterministic body geometry is not known precisely
  • Orientation-averaged or ensemble-style weak-scattering predictions
  • Situations where fully coherent DWBA overpredicts narrow interference structure

Supports

  • FLS objects with the same geometry support as DWBA
  • Monostatic target strength based on an averaged linear backscatter quantity
  • The same local contrast notation as DWBA, with seawater as medium 1 and the body as medium 2

Main assumptions

  • Weak-scattering fluid-like body
  • Phase variability enters statistically rather than through an explicit new boundary-value solve
  • Randomization acts on the coherent sum rather than on the local scattering kernel

Validation status

  • Benchmarked against the canonical spectra stored in benchmark_ts.
  • Validated against the CCAMLR, NOAA applet, and echoSMs implementations.

Family pages

  • Implementation: stochastic settings, spectra, and validation workflows
  • Theory: randomized coherent sums and scale-invariant phase statistics

References

Conti, Stéphane G., and David A. Demer. 2006. “Improved Parameterization of the SDWBA for Estimating Krill Target Strength.” ICES Journal of Marine Science 63 (5): 928–35. https://doi.org/10.1016/j.icesjms.2006.02.007.
Demer, David A., and Stephane G. Conti. 2003. “Reconciling Theoretical Versus Empirical Target Strengths of Krill: Effects of Phase Variability on the Distorted-Wave Born Approximation.” ICES Journal of Marine Science 60 (2): 429–34. https://doi.org/10.1016/S1054-3139(03)00002-X.
Demer, David A., and Stéphane G. Conti. 2003. “Validation of the Stochastic Distorted-Wave Born Approximation Model with Broad Bandwidth Total Target Strength Measurements of Antarctic Krill.” ICES Journal of Marine Science 60 (3): 625–35. https://doi.org/10.1016/S1054-3139(03)00063-8.
Demer, David A., and Stéphane G. Conti. 2005. “New Target-Strength Model Indicates More Krill in the Southern Ocean.” ICES Journal of Marine Science 62 (1): 25–32. https://doi.org/10.1016/j.icesjms.2004.07.027.