Ripples on sea surface take the direct responsibility on back-scattering of radar waves at air-sea interface. They are modulated and respond differently under various atmospheric conditions. In present study, various atmospheric stability conditions are simulated in a large wind-wave flume. A two-dimensional scanning laser slope gauge is developed to map surface slope of ripple. From the direct measurements on ripples, the stability effects on normalized cross-section of radar backscattering, σ_o, are derived according to the principle of Bragg-resonant backscattering of radar waves. Present result indicates that σ_o is enhanced under unstable conditions and vice versa for stable situations. Different from traditional concept that wind-friction velocity can imply the atmospheric stability effects and fully define ripple structures and σ_o, present study indicates an opposite result. In order to setup accurate radar remote sensing model, a stability parameter besides the wind-friction velocity is necessary.
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