The Tibetan Plateau is regarded as the Earth's Third Pole, which is the source region of several major rivers that impact more 20% the world population. This high-altitude region is reported to have been undergoing much greater rate of weather changes under global warming, but the existing reanalysis products are inadequate for depicting the state of the atmosphere, particularly with regard to the amount of precipitation and its diurnal cycle. An ensemble Kalman filter (EnKF) data assimilation system based on the limited-area Weather Research and Forecasting (WRF) model was evaluated for use in developing a regional reanalysis over the Tibetan Plateau and the surrounding regions. A 3-month prototype reanalysis over the summer months (June−August) of 2015 using WRF-EnKF at a 30-km grid spacing to assimilate nonradiance observations from the Global Telecommunications System was developed and evaluated against independent sounding and satellite observations in comparison to the ERA-Interim and fifth European Centre for Medium-Range Weather Forecasts Reanalysis (ERA5) global reanalysis. Results showed that both the posterior analysis and the subsequent 6- to 12-hr WRF forecasts of the prototype regional reanalysis compared favorably with independent sounding observations, satellite-based precipitation versus those from ERA-Interim and ERA5 during the same period. In particular, the prototype regional reanalysis had clear advantages over the global reanalyses of ERA-Interim and ERA5 in the analysis accuracy of atmospheric humidity, as well as in the subsequent downscale-simulated precipitation intensity, spatial distribution, diurnal evolution, and extreme occurrence.
Bibliographical noteFunding Information:
The authors thank Yue Ying and Robert Nystrom for their helpful advice and codes. Jie He is supported by the China Scholarship Council. This work is primarily sponsored by the U.S. National Science Foundation (AGS-1712290), the U.S. Department of Energy project WACCEM, the Strategic Priority Research Program of Chinese Academy of Sciences (grant XDA20060401), the Swedish STINT (grant CH2015-6226), the Swedish VR (grant 2017-03780),?the Gothenburg Chair Programme for Advanced Studies (GoCAS), and the National Research Foundation of South Korea (grant 2017R1E1A1A03070968). Computer sources from the ADAPT of PSU are provided to run the experiments at the Texas Advanced Computing Center (TACC). The data sets evaluated in this paper are archived and accessible on the stampede2 cluster of TACC (http://www.tacc.utexas.edu).
All Science Journal Classification (ASJC) codes
- Global and Planetary Change
- Environmental Chemistry
- Earth and Planetary Sciences(all)