2017 Fiscal Year Research-status Report
Developing 2-way feedback nested-domain LETKF data assimilation system and application to high-resolution typhoon analyses and forecasts
| Project/Area Number |
17K14396
|
|---|
| Research Institution | Institute of Physical and Chemical Research |
|---|
Principal Investigator |
Lien GuoYuan 国立研究開発法人理化学研究所, 計算科学研究機構, 特別研究員 (50744257)
|
|---|
| Project Period (FY) |
2017-04-01 – 2019-03-31
|
| Keywords | データ同化 / 台風 / 気象学 |
|---|
| Outline of Annual Research Achievements |
The online nested-domain LETKF has been newly implemented in the SCALE-LETKF system. Combined with the existing online nested-domain function in the SCALE-RM model, the SCALE-LETKF is now capable of running both data assimilation cycles and extended ensemble forecasts with multiple nested domains in an online framework. This new function can greatly save the human effort of conducting nested-domain data assimilation experiments compared to the old offline approach. To reduce the unnecessary disk I/O and thus improve the computational efficiency, both the ensemble model forecasts and the LETKF are conducted using single MPI programs. Currently the LETKF analysis using the online nesting function is identical to that using the offline approach. The 2-way feedback LETKF analysis with multiple nested domains is being developed, which is expected to improve the accuracy of the multiple-domain LETKF analysis.
The data assimilation experiments with the September 2015 Kanto-Tohoku Heavy Rainfall case have been conducted using this new online nesting function. Preliminary results show that, compared with the old offline downscaling experiment in Lien et al. (2017, SOLA), the online nested-domain experiment leads to improved forecast skill, due to further performing LETKF analysis in the inner high-resolution domain and frequent coupling of the two domains in the model forecast steps.
In addition, related typhoon data assimilation studies conducted using the SCALE-LETKF system have been published by Honda (2018a,b, MWR, JGR), which the principal investigator coauthored.
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The development work of the online nested-domain function in the SCALE-LETKF has been conducted smoothly. The system has been ready for conducting general online nested-domain data assimilation experiments although without the 2-way feedback analysis, which will be implemented soon. In addition, a typhoon case study has been conducted using the new online nesting function with the SCALE-LETKF, and it shows promising results compared to the previous offline downscaling experiments.
|
| Strategy for Future Research Activity |
Research plan for FY2018:
1. Develop new SCALE-LETKF functions specially for typhoons: a) Complete implementing the 2-way feedback nested-domain LETKF with the SCALE-LETKF system. b) Develop vortex-tracking moving nested domains for model forecasts and the LETKF.
2. Test the typhoon data assimilation with the SCALE-LETKF by case studies: a) With the September 2015 Kanto-Tohoku Heavy Rainfall case, conduct an online nested-domain experiment using the 2-way feedback LETKF scheme, and compare the results with the traditional scheme that performs independent analyses for each domain. b) Choose another case with a more intense typhoon and conduct similar experiments to investigate the benefit of the online nested-domain data assimilation system. c) If the vortex-tracking moving nested domain function can be ready, conduct case study experiments with vortex-tracking moving nested domains to allow using higher model resolution in the innermost domain.
|
| Causes of Carryover |
Travel supports, such as those for the principal investigator to attend conferences in order to present the achievement to the community are needed. The journal publication fee is also included in the usage plan. In addition, a disk storage is planned to be bought to store the research data produced by this project.
|
