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1. Full name: Bui Minh Tuan 2. Sex: Male
3. Date of birth: 18/03/1988 4. Place of birth: Thai Binh
5. Admission decision number: 2999/QĐ-ĐHKHTN
6. Changes in academic process:
7. Official thesis title: Intraseasonal oscillation of rainfall in Vietnam
8. Major: Meteorology 9. Code: 9 440222.01
10. Supervisors: PGS. TS. Nguyễn Minh Trường
11. Summary of the new findings of the thesis
Based on the first four principle modes of intra-seasonal oscillation (ISO) of rainfall in Vietnam, the author pointed out that the ISO of rainfall is distinct from region to region in Vietnam duo to topography effect and extra-tropical forcing. The activities of the rainfall ISO display a strong relation with the occurrence of heavy rainfall in Vietnam.
Based on the large-scale patterns associated with rainfall ISO, the author pointed out that rainfall ISO in Vietnam is largely modulated by extra-tropical factors. In mode 1, rainfall ISO is caused by the interaction between cold surge from Siberian and tropical depression type wave (TD-type wave). In mode 2, rainfall ISO is induced by the convergence of cold air mass from polar regions and TD-type wave. In mode 3, rainfall ISO is results of quasi-geostrophic lifting and TD-type wave. At last, the upstream development of the extra-tropical wave train originating from the North
Pacific strengthens the convergent flows of the TD-type wave.
The interactions of moisture divergence, radiative heating and diabatic heating caused by downward motions play significant roles in development of conditional instability, leading to the establishment of deep convection in active phase of rainfall ISO in Vietnam. However, the cooling down of lower troposphere (because of evaporation) associated with the diabatic heating in the middle of troposphere that stabilizes the environment. This negative feedback leading to the end of active phase and the beginning of break phase in rainfall ISO in Vietnam.
12. Practical applicability, if any:
The results can be considered as theoretical basis to construct new methods to predict rainfall in Vietnam with a longer range. It takes time for the ISO signal propagate to Vietnam, if forecasters can detect that signal, they can use statistical and dynamical methods to make a weather report with a range up to 20 days or more. The results can be used to verify the ability of weather and climate model in simulation specific process in the atmosphere.
The thesis pointed out the relation of rainfall ISO and the occurrence heavy rainfall in Vietnam. This result is the basis to construct new method to predict heavy rainfall. Because heavy rainfall is an extreme event, it is rare and cannot be simulated by numerical model. We expect that the heavy rainfall can be predicted more accurate in our further investigation.
13. Further research directions, if any
- Constructing new methods for operational extended range forecast for rainfall in Vietnam.
- Investigating the multi-scale interaction leading to the establishment of deep convection in Vietnam
14. Thesis-related publications:
1. Truong, N. M., and B. M. Tuan, 2018: Large‐scale patterns and possible mechanisms of 10–20‐day intra‐seasonal oscillation of the observed rainfall in Vietnam. International Journal of Climatology, 38, 3801-3821.
2. Tuan, B.M., 2019: Extra-tropical Forcing of Submonthly Variations of Rainfall in Vietnam. J. Climate, 32, 2329–2348. https://doi.org/10.1175/JCLI-D-18-0453.1
3. Truong, N. M., and B. M. Tuan, 2019: Structures and Mechanisms of 20−60-day Intra-seasonal Oscillation of the Observed Rainfall in Vietnam. Journal of climate. J. Climate, 32, 5191–5212. https://doi.org/10.1175/JCLI-D-18-0239.1
4. Bùi Minh Tuân, Nguyễn Minh Trường, Vũ Thanh Hằng, Công Thanh, 2016: Sự dịch chuyển lên phía bắc của dao động nội mùa và cơ chế dao động nội mùa của lượng mưa tại Bắc Bộ và Nam Bộ. Tạp chí Khoa học ĐHQGHN. Các Khoa học Trái đất và Môi trường, Tập 32, Số 3S, 2016243
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