A wavelet‐based analysis of convective organization in ICON large‐eddy simulations

Abstract

Wavelet spectra of rain rates are used to characterize convective organization in high‐resolution simulations (horizontal grid spacing 156 m) with the large‐eddy model ICON‐LEM over Germany. Scattered convection takes place on scales between 1.2 and 4.8 km, while organized structures like supercells or mesoscale convective systems act on scales above 4.8 km. Organization of convection within squall lines is visible in the spectra as spectral energy is increased in certain directions. We further investigate the dynamical properties that relate to convective organization, and highlight the role of parameters such as CAPE and wind shear.

Preferred spatial scale, average convective rain rate and anisotropy as inferred from the wavelet spectra are important characteristics to quantify convective organization. They are used to introduce a wavelet‐based organization index (WOI). Compared with other indices for convective organization, WOI does not require the definition of objects. Using the WOI we are able to distinguish organized from non‐organized convection.