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Mechanisms of Orographic Precipitation over Mt. Da-Tun Associated with Typhoon Meari (2011)
Typhoon precipitation,Orographically enhanced precipitation,Upslope lifting,Seeder-feeder mechanisms,Rainfall enhancement of convective cells,
|Publication Year :||2019|
With temporally and spatial high-resolution rain gauge data and Doppler radar observations, this study is aimed to explore the physical mechanisms responsible for the orographic precipitation associated with Typhoon Meari (2011). The occurrence of heavy precipitation for this typhoon event was concentrated over Mt. Da-Tun as Meari passed over regions ~300 km northeast of Taiwan and brought strong northerly/northwesterly flow (20-25 m s-1) impinging on northern Taiwan. Mt. Da-Tun, the study area, is a three-dimensional, isolated mountain barrier located adjacent to the northern coast of Taiwan and has terrain peaks at approximately 1 km (MSL, Mean Sea Level).Intense rainfall (>250 mm) was observed nearby the mountain crest of Mt. Da-Tun within 10 h during the period of primary interest. Analyses indicate that the layer of orographic enhancement of precipitation was primarily confined to the lowest 2 km (MSL). The enhanced rainfall was observed to be 2-3 times greater than the typhoon background precipitation.
By tracking hydrometeor trajectory and performing theoretically quantitative calculations, it is found that the increased amount of precipitation water as elevated hydrometeors fell into the low levels was closely related to the precipitation enhancement due to seeder-feeder processes. The enhanced precipitation over mountains is much better quantified by theoretical accretion rate than upslope-lifting-induced precipitation. Moreover, the seeder-feeder calculation tended to be underestimated and have larger errors, when convective elements of intense reflectivity embedded within typhoon background precipitation moved into Mt. Da-Tun. In addition to the seeder-feeder effect that is more suitable for stratiform background precipitation scenario, the rapid modification of airflow and precipitation associated with landfalling convective elements by topography is also an important process contributing to the orographic enhancement of precipitation for the present case.
|Appears in Collections:||大氣科學系|
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