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Title: The effect of a river delta and coastal roughness variation on a landfalling tropical cyclone
Other Titles: San jiao zhou he yan hai cu cao du bian hua dui deng lu re dai qi xuan de ying xiang
Authors: Au-Yeung, Yee Man (歐陽綺雯)
Department: Department of Physics and Materials Science
Degree: Master of Philosophy
Issue Date: 2009
Publisher: City University of Hong Kong
Subjects: Cyclones -- Tropics.
Notes: CityU Call Number: QC941 .A88 2009
xiii, 74 leaves : ill. (some col.) 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2009.
Includes bibliographical references (leaves 69-72)
Type: thesis
Abstract: Numerical simulations on an f plane are performed using the Weather Research Forecasting (WRF) model to study how the presence of a river delta and variations in coastal roughness might affect the motion and the structure of a tropical cyclone (TC) near landfall. A spun-up TC is placed 135 km from a north-south oriented coastline. In each delta experiment, an idealized triangular-shaped delta, pointing to the west with length 150 km and a river mouth size of 100 km is inserted along the coastline. The land surface roughness and the moisture availability of the delta vary among the delta experiments. In another set of experiments, where there is no delta, the roughness of a whole land area has different values along the north-south oriented coast. The results of both sets of experiments are compared to the control (CTRL) where there is no delta and no roughness variation along the coast (its whole land area is rough). Results suggest that the TC in the CTRL experiment is weaker than all the delta cases during a certain period before landfall. Moisture supply from the delta appears to have an effect on sustaining the approaching TC, despite the relatively small scale of the delta. The TCs in the roughness variation experiments have tracks differ from that of the CTRL. The roughness variation along the coast affects the convergence patterns – higher roughness induces stronger convergence and hence increases the vertical advection term in the PVT distribution over the rougher area. Hence, a TC tends to move into a region with higher roughness. These results suggest that numerical predictions of TC landfall should have a good representation of the land configuration in the model.
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