Effects of Nonlinearity on the Atmospheric Flow Response to Low-Level Heating in a Uniform Flow

Abstract

Abstract Effects of nonlinearity on the stably stratified atmospheric response to prescribed low-level heating in a uniform flow are investigated through nondimensional numerical model experiments over a wide range of the nonlinearity factors of thermally induced finite-amplitude waves (0 ≤ μ ≤ 4). The heating function is assumed to be uniform in the vertical from the surface to a nondimensional height of 2 and to be bell shaped in the horizontal. As the nonlinearity factor becomes larger, the flow response is quite different from the linear response due to the larger nonlinear advective effect. A strong updraft cell gradually appears on the downstream side with an increasing nonlinearity factor. In the highly nonlinear regime (μ ≥ 2.2), alternating weaker downdraft and updraft cells behind the leading updraft cell are observed on the downstream side. These alternating cells experience periodic cycles with the processes of linear and nonlinear advection, intensification, weakening, formation, disappearing...