PNNL

Abstract

This study examines boundary layer turbulence derived from high temporal resolution meteorological measurements from 40 research flights over the western North Atlantic Ocean during the 2020 deployments of ACTIV A TE. Frequency distributions of various turbulent quantities reveal stronger turbulence during the winter flights than in summer and for cloud-topped than in cloud-free boundary layers. Maximum turbulent kinetic energy is most often within cloud from observations in winter and summer, whereas it is mostly below cloud in both seasons by a global model turbulence parameterization. Bivariate frequency distributions are generally binormal, validating a key assumption in higher-order turbulence/shallow convection parameterizations used by some global models. Turbulence simulated by global models using such parameterizations is not as strong as observed, suggesting that the treatment of turbulence in Earth system models still needs to be further improved.