Evaluation of two turbulence schemes in representing UTLS turbulence generated by orographic gravity waves

Interactions within the upper troposphere/lower stratosphere (UTLS) region of the atmosphere play a crucial role in shaping climate change predictions by affecting the distribution of greenhouse gases. The transport of such tracers across this area is governed by a range of dynamic processes operating on multiple scales. On the smallest scales, turbulence is responsible for the irreversible mixing of tracers. Acting on subgrid scales, turbulence needs to be parameterized in weather and climate models. Turbulence within the UTLS region differs from that in the atmospheric boundary layer (ABL) due to stable stratification and the absence of a solid boundary. Various sources contribute to UTLS turbulence, including jet streams, overshooting convection, unbalanced flows, and gravity wave breaking.  With its unique characteristics, turbulence in the UTLS region is still relatively poorly understood when compared to its counterpart in the ABL. Traditional turbulence parameterizations, developed for the ABL, do not take into account the complex, non-homogenous, anisotropic, and patchy nature of the stratified UTLS turbulence. Hence there is a need for adapting ABL turbulence schemes to reflect the characteristics of turbulence in the UTLS region. As a first step, our study compares the characteristics of mountain-wave generated UTLS turbulence for two turbulence schemes: the operational turbulence scheme in the ICOsahedral Non-hydrostatic (ICON) model and a new scheme, the two-turbulence energies scheme coupled to the assumed probability density function method (2TE+APDF). We assess the performance of the two schemes in capturing turbulence features by simulating mountain waves during two field campaigns, the DEEPWAVE campaign over New Zealand and the SouthTRAC campaign over South America. Our goal is to improve the 2TE+APDF scheme for the representation of UTLS turbulence related to mountain waves and to develop an optimized setup for UTLS mountain wave simulations with the ICON model.