Project B03:
Deep exchange with the UTLS: the Tibetan pipe

Brief Summary

This project aims to improve the understanding of and quantify the role of the highest mountain ranges and plateaus in the transport of water vapor, other trace gases, and aerosols between the atmospheric boundary layer (ABL) and the UTLS. Reaching this goal will improve the understanding of the climate system and enhance the ICON-based climate modeling system that will be used and adapted in this project. Within the first phase of the CRC we will focus on ABL to UTLS exchange processes over the geographical area of the Tibetan plateau (TiP) and the Himalayas with its foothills. We plan to investigate two transport mechanisms: (a) dry deep mixing with tropopause folds and very deep ABLs (up to 5 km above the plateau level) in boreal winter and spring, and (b) deep convection over the TiP, the Himalayas, and Himalayan foothills in the monsoon season.
In winter and spring, deep convective ABLs (CBLs) frequently occur over the TiP. These deep CBLs lead to a strong coupling of near-surface air with the upper troposphere (UT) and enable the rapid transport of near-surface tracers into the UT (and vice versa). The UT is then coupled on longer time scales via quasi-horizontal transport with the lower stratosphere (LS), making the TiP, not only in the monsoon season, a global hotspot of troposphere-stratosphere exchange.
The Asian Mainland, including the TiP, is one of the primary source regions of deep convective transport into the UTLS, in particular in boreal summer. The project plans to investigate the unique deep convective and turbulent mixing processes over the TiP and beneath the Asian summer monsoon upper level anticyclone, which are not well represented in present day reanalyses and climate model simulations.
The project studies both transport mechanisms using a multi-scale modeling approach, including tracer and trajectory methods. Realistic and idealized modeling experiments using ICON in global parameterized convection (zoomed over the Asian monsoon region to D∼13 km), in limited-area convection-permitting (Dx∼3 km), and large-eddy simulation (Dx∼200 m) setups. This multi-scale approach will improve the understanding of the lifting processes in this active transport region and will deliver transport benchmarks for coarser-grid chemistry-transport and climate models.
The following CRC phases will extend the modeling-based process studies to other high mountain ranges and high plateau regions. These studies will test and extend the generated understanding and shall include explicit trace gases and aerosol in the transport modeling. Finally, we plan a climatic quantification of deep exchange in the different high and complex orography geographic regions compared to the deep exchange in other transport regions (like the storm track regions over the North Atlantic and North Pacific).

Members

Publications

Singh, P. and B. Ahrens (2023): Modeling Lightning Activity in the Third Pole Region: Performance of a km-Scale ICON-CLM Simulation. Atmosphere 14 (11), doi: 10.3390/atmos14111655.

Prein, A. F., N. Ban, T. Ou, J. Tang, K. Sakaguchi, E. Collier, S. Jayanarayanan, L. Li, S. Sobolowski, X. Chen, X. Zhou, H.-W. Lai, S. Sugimoto, L. Zou, S. u. Hasson, M. Ekstrom, P. K. Pothapakula, B. Ahrens, R. Stuart, H. C. Steen-Larsen, R. Leung, D. Belusic, J. Kukulies, J. Curio, and D. Chen (2023): Towards Ensemble-Based Kilometer-Scale Climate Simulations over the Third Pole Region. Climate Dynamics 60, (11), 4055–4081. doi: https://doi.org/10.21203/rs.3.rs-1570621/v1.