Benchmarking in a rotating annulus: a comparative experimental and numerical study of baroclinic wave dynamics

TL;DR

This study compares experimental and numerical results of baroclinic wave dynamics in a rotating annulus, creating benchmarks for atmospheric model validation through detailed analysis of wave patterns and behaviors.

Contribution

It provides a comprehensive comparison between laboratory experiments and numerical simulations of baroclinic waves, establishing benchmark cases for future atmospheric model testing.

Findings

Good agreement between experiments and simulations in wave patterns

Identification of dominant wave modes and drift rates

Benchmark datasets for model validation

Abstract

The differentially heated rotating annulus is a widely studied tabletop-size laboratory model of the general mid-latitude atmospheric circulation. The two most relevant factors of cyclogenesis, namely rotation and meridional temperature gradient are quite well captured in this simple arrangement. The radial temperature difference in the cylindrical tank and its rotation rate can be set so that the isothermal surfaces in the bulk tilt, leading to the formation of baroclinic waves. The signatures of these waves at the free water surface have been analyzed via infrared thermography in a wide range of rotation rates (keeping the radial temperature difference constant) and under different initial conditions. In parallel to the laboratory experiments, five groups of the MetStr\"om collaboration have conducted numerical simulations in the same parameter regime using different approaches and solvers, and applying different initial conditions and perturbations. The experimentally and numerically obtained baroclinic wave patterns have been evaluated and compared in terms of their dominant wave modes, spatio-temporal variance properties and drift rates. Thus certain ``benchmarks'' have been created that can later be used as test cases for atmospheric numerical model validation.