Analyses of internal solitary waves generated at the Columbia River plume front using SAR imagery

Abstract

Internal solitons generated at the Columbia River plume front during ebb tide are displayed on a synthetic aperture radar (SAR) image taken on 26 July 2004 at 14:24:22 UTC. Scale analyses suggest that these internal solitons belong to the finite‐depth category. A theoretical model, relating the radar backscatter cross section to dynamic parameters of internal solitons in the continuous stratification, is developed. Using the model and background stratification data collected by the River Influences on Shelf Ecosystem (RISE) project in July 2004, we extract the soliton dynamic parameters of the half‐width, amplitude, phase speed, and average energy flux per crest length along a typical section across the internal solitons. The observed stratification is simulated by using a theoretical model parameterized by pycnocline depth, thickness, and maximum buoyancy frequency. The half‐width, amplitude, phase speed, and energy flux of the leading soliton at the section are 119.3 m, 9.3 m, 0.69 m s−1, and 417.4 W m−1 with the uncertainty ranges of ±14.7 m, ±2.6 m, ±0.10 m s−1, and ±281.6 W m−1, respectively. Sensitivity analyses reveal that the extraction of the soliton half‐width from the SAR image is not affected by the stratification. The amplitude is less influenced by the pycnocline thickness than the depth and is independent of the maximum buoyancy frequency.