A Study of Objective Synoptic Analysis Technique to Identify the Ddistribution of rainfall band in Tropical Cyclones-Using Typhoon Morakot as an Example

• Main Authors: CHEN,YU-JHANG, 陳昱璋
• Other Authors: YANG,HORNG-YU
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/34411906715083882667

碩士 === 中華科技大學 === 土木防災工程研究所 === 98 === Torrential rain brought by typhoon has been one of the major disasters in Taiwan. In particular, the flooding and landslides from downpours brought by Typhoon have been causing losses of life and property almost every year in Taiwan. In order to make people understand whether typhoon warnings issued by government officials are appropriate and accurate, a standard of objective assessment must be determined in the precondition. When typhoon attacks Taiwan, its circulation is affected by the topography of Taiwan, which is often associated with meso-scale phenomenon in the local area. Hence, research results of open surface waters in the past can not be used as the basis for the explanation of typhoon characteristics in Taiwan. Currently, it is still a challenge to forecast the accumulated precipitation produced by typhoon attacks in Taiwan. The forecast of accumulated precipitation is frequently adjusted as typhoon circulation approaches the land. Therefore, early warnings of disaster are greatly limited. This study attempts to develop a fast and efficient method that estimates accumulated precipitation brought by typhoon. The traditional formula that forecasts the quantity of typhoon’s precipitation has been empirical. However, this study is based on a model that extracts existing rainfalls from the typhoon path, and is established according to distances between observation stations. Therefore, the complexity between typhoon factors and rainfall quantity is appropriately included in the forecast model. If the values of typhoon factors can be forecasted reliably, the rainfall quantity can be calculated swiftly, allowing the necessary timeline for the task of typhoon forecast being satisfactory. Using Typhoon Morakot as a case study that precipitation data brought by its path and its central path as the identification source of cloud separation, this research evaluated how observed rainfall data and problems associated with weather variation can be sorted out. Moreover, Objective Synoptic Analysis Technique (OSAT) may be carried out for the identification to establish the model of parameters. The relationship between the distance of observation stations and regional rainfalls was analyzed for the comparison of effective separation in order to understand the relationship between tropical cyclone (typhoon) and local circulation. Finally, this model was validated through the rainfall data of forecasted values and actual values. The results of this study showed that this method can effectively identify clouds for the quantity of rainfalls, as well as dividing the levels of tropical cyclone (typhoon) that affect rainfall, ensuring that the forecast of rainfall distribution is under control. By drawing out the range of rainfall band for the observation stations, actual parameters were carried out more objectively for the analysis of the weather system that influences precipitation, as well as reasonably handling the condition of precipitation.