A comparison of two heavy rainfall events during the terrain-influenced monsoon rainfall experiment (TiMREX) 2008
Journal
Monthly Weather Review
Journal Volume
142
Journal Issue
7
Pages
2436-2463
Date Issued
2014
Author(s)
Abstract
Two contrasting localized heavy rainfall events during Taiwan's early summer rainy season with the daily rainfall maximum along the windward mountain range and coast were studied and compared using a combination of observations and numerical simulations. Both events occurred under favorable large-scale settings including the existence of amoisture tongue from the tropics. For the 31 May case, heavy rainfall occurred in the afternoon hours over the southwestern windward slopes after a shallowsurface front passed central Taiwan. The orographic lifting of the prevailing warm, moist, west-southwesterly flow aloft, combined with a sea breeze-upslope flow at the surface provided the localized lifting needed for the development of heavy precipitation. On 16 June before sunrise, pronounced orographic blocking of the warm, moist, south-southwesterly flow occurred because of the presence of relatively cold air at low levels as a result of nocturnal and rain evaporative cooling. As a result, convective systems intensified as they moved toward the southwestern coast. During the daytime, the cold pool remained over southwestern Taiwan without the development of onshore/upslope flow. Furthermore, with a south-southwesterly flow aloft parallel to terrain contours, orographic lifting aloft was absent and preexisting rain cells offshore diminished after theymoved inland.Over northern Taiwan on the lee side, a sea breeze/onshore flow developed in the afternoon hours, resulting in heavy thundershowers. These results demonstrate the importance of diurnal and local effects on determining the location and timing of the occurrences of localized heavy precipitation during the early summer rainy season over Taiwan. © 2014 American Meteorological Society.
Subjects
Diurnal effects; Field experiments; Local effects; Mesoscale processes; Numerical weather prediction/forecasting; Orographic effects
Other Subjects
Atmospheric movements; Evaporative cooling systems; Landforms; Parallel flow; Diurnal effects; Field experiment; Local effects; Mesoscale process; Numerical weather prediction/forecasting; Orographic effects; Rain; cold pool; comparative study; convective system; experimental study; field survey; mesoscale meteorology; mountain region; orographic effect; precipitation intensity; rainfall; sea breeze; summer; terrain; topographic effect; wind direction; Taiwan
Type
journal article