Using WRF Model to Investigate the Impact of Orographic Effect on Heavy Rainfall Case During SoWMEX IOP3.

• Main Authors: Szu-han Chiu, 邱思翰
• Other Authors: Pay-liam Lin
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/91803317045530452126

碩士 === 國立中央大學 === 大氣物理研究所 === 98 === In May 30, 2008, a Mei-Yu Front system passed over Taiwan, bringing heavy rainfall to northern Taiwan. In May 31, a convective cell was generated at western Taiwan. This convective system associated with the front to move into Taiwan area. It caused heavy rainfall and the maximum rainfall rate reached 40mm/hr in the mountains area of northern Pingtung. Later, this system moved out of Taiwan accompanied with the front and dissipated, gradually. This study uses WRF model to investigate how the terrain of Taiwan influence on the generation and enhancement of the convective cell and the movement of the extreme rainfall location. In this study, several sensitivity experiments with different terrain heights of Taiwan are performed to verify the impact of terrain on the development of convective system. The sensitive tests contain three different terrain heights including CTRL run (full-terrain), HTRN run(half-terrain), and NTRN run(no-terrain). The results of CTRL run(FR ≒ 0.4) show that the formation of this convective system is closely related to terrain effects. The airflow was blocked by the Taiwan Central Mountain Range, so that the wind direction was changed from southwestly to southly and converges with the frontal northeasterly and provide favorable condition for the formation of the convective system. When the terrain height is reduced, the generation location of convective system moves into inland. If the terrain is removed, the convective cell will be not generated. After the convective system moved into the inland area, the southly airflow resulted from the blocking effects of Taiwan terrain continuously converge with the northly. This convergence provide a favorable condition for the enhancement and maintain of the the convective system. The rainfall maximum was located at the windward slope. However, in the HTRN experiment, the southly wind resulted from the terrain blocking effect became weak due to the terrain height is reduced to the half. The intensity of the convective system can not be maintained when it moved into the island area.