Global measures of local convective instabilities

We examine the linear stability of the Ginzburg-Landau operator with spatially varying coefficients, which mimics strongly nonparallel open flows such as wakes, jets, and boundary layers. The streamwise non-normality of the global eigenmodes explains the observed large transient growths, classically interpreted in terms of local convective instability. The use of pseudospectra provides an exact measure of spatial amplification and aids in the determination of when entrance noise dominates the open-flow dynamics.