應用ENSO指標建立乾旱機率預報模式─以台灣南部地區為例

Development of Drought Probability Forecasting Models Based on ENSO Indices-A Case Study in Southern Taiwan

郭志豪(Chih-Hao Kuo) ； 楊道昌(Tao-Chang Yang) ； 郭振民(Chen-Min Kuo) ； 陳憲宗(Shien-Tsung Chen) ； 游保杉(Pao-Shan Yu)

《農業工程學報》 58卷1期 (2012/03) Pp. 13-32

https://doi.org/10.29974/JTAE.201203.0002

摘要

Although Taiwan receives much precipitation, it is an area prone to suffer droughts due to uneven temporal distribution of precipitation and small storage capacity of reservoirs. Therefore, how to make drought early warning and protection against possible losses of life and property has been an essential issue in Taiwan. This study collected the information of Pacific large scale circulation patterns. i.e., ENSO indices, and the historical rainfall records from 7 rain gauges in southern Taiwan for calculating the values of three-month standardized precipitation index (SPI3) during 1950 to 2009. Based on the theory of Markov chains, this study calculated the frequencies in the intervals among different variables (e.g., ENSO indices and SPI3) for building state transition probability matrixes to establish drought probability forecasting models. Different combinations of variables make different forecasting models. Therefore, for reducing the forecasting uncertainty of a single-model, the approach of multi-model ensemble (MME) which ensembles all single-model results was used to forecast the SI'I3 probability distribution l- month ahead by using the ENSO indices at the present time as predictors. The results show that the proposed models can well perform in providing short-term early warning of droughts in southern Taiwan and can be used to assess the long-term dry or wet conditions during a given period. For example, the ratio of the occurrence probabilities of SPI3 ＜ 0 to SPI3 ＞ 0 in southern Taiwan is 6:4 during 2001 to 2009, which reveals that the weather pattern was prone to dry condition during the period.

關鍵字

標準化降雨指標 ； ENSO ； 狀態轉移機率 ； 多模式系集 ； 乾旱機率預報

並列摘要

Although Taiwan receives much precipitation, it is an area prone to suffer droughts due to uneven temporal distribution of precipitation and small storage capacity of reservoirs. Therefore, how to make drought early warning and protection against possible losses of life and property has been an essential issue in Taiwan. This study collected the information of Pacific large scale circulation patterns. i.e., ENSO indices, and the historical rainfall records from 7 rain gauges in southern Taiwan for calculating the values of three-month standardized precipitation index (SPI3) during 1950 to 2009. Based on the theory of Markov chains, this study calculated the frequencies in the intervals among different variables (e.g., ENSO indices and SPI3) for building state transition probability matrixes to establish drought probability forecasting models. Different combinations of variables make different forecasting models. Therefore, for reducing the forecasting uncertainty of a single-model, the approach of multi-model ensemble (MME) which ensembles all single-model results was used to forecast the SI'I3 probability distribution l- month ahead by using the ENSO indices at the present time as predictors. The results show that the proposed models can well perform in providing short-term early warning of droughts in southern Taiwan and can be used to assess the long-term dry or wet conditions during a given period. For example, the ratio of the occurrence probabilities of SPI3 ＜ 0 to SPI3 ＞ 0 in southern Taiwan is 6:4 during 2001 to 2009, which reveals that the weather pattern was prone to dry condition during the period.

並列關鍵字

Standardized precipitation index ； ENSO ； State transition probability ； Multi-model ensemble ； Drought probability forecasting