The Third Pole (TP) is the Tibetan Plateau and surrounding mountain ranges. It has the world's largest storage of ice and snow outside the Arctic and Antarctic. The TP plays a significant role in the global climate system and is highly sensitive to human-induced climate change. With several major rivers originating from the TP that impact more than 20% of the world population, changes to its cryosphere has far-reaching ramifications on hydrological regimes, ecosystems, and water security.
Because of its complex terrain and harsh environment, ground-based observations are scarce. This hampers efforts to study regionally important physical processes and systems over the TP where the spatial scale of annual precipitation is generally small and convection system contributes significantly to the total precipitation. Thus, we will investigate the impact of convection system on the water cycle, especially precipitation over the TP. Horizontal resolution of prevailing global reanalysis datasets is generally coarser than 30 km, which is not sufficient to examine convection and other mesoscale systems over the TP. A high-resolution regional downscaling project focusing on the TP region has the potential to vastly improve the understanding of physical processes in this region and beyond, paving the way for future physically plausible climate projections. This project aims to enhance our understanding of the water cycle over the TP, with an initial focus on assessing model skill in the simulation of convection and precipitation, building towards skillful multi-year simulation of the regional precipitation and hydrological regime.
The Advanced Research version of the Weather Research and Forecasting model (WRF-ARW) will be used in this project. The targeted resolution is 2-9 km with a focus on convection-permitting simulations (2-4 km). The fifth generation of global reanalysis from the ECMWF, ERA5, with a horizontal resolution of 31km, will be used to drive the simulations. Impacts of different parameterizations of cloud microphysics, boundary layer turbulence, complex terrain-induced drag and hydrological cycle, land-surface interactions, and other small-scale physical processes on the simulated convection and associated precipitation will be evaluated. A test of one-year simulation will be done that will be evaluated by both satellite and in situ observations. When this is done successfully, we plan to run a subset of model setups for a multi-year period between 2000 and 2018.
The outcomes of the project are expected to enhance our understanding of physical processes relevant for clouds and precipitation formation (solid and liquid phases), convection, and local wind system. They should also be useful to future high-resolution regional climate modeling and develop a regional reanalysis over the TP and beyond. Studies on the water cycle will also benefit tremendously from the results of this project.
This project is the Swedish contribution to a new endorsed WCRP-CORDEX Flagship Pilot Studies (FPS) about high-resolution climate modeling over the TP. There are 20 international research groups participated in the FPS while the PI of this project is the coordinator of the FPS.