臺灣地區年際異常氣象狀況對農業生產之影響

Abstract

本研究依據環繞臺灣地區的10 個中央氣象局平地氣象站，自1949-2003 年的觀測資料，整理各地區每年低溫(≤10℃)與高溫(≥30℃)的日數、日絕對最低與最高氣溫、年累積降雨量與降雨(≥1.0mm)日數、日最大降雨強度等項目，以及1959-2003 年的侵臺颱風數目，以瞭解屬於全面性之異常氣象狀況的發生情形。再以十年為週期統計分析各災害性天氣狀況的發生趨勢，並與農業氣象災害損失程度進行關聯性分析。分析結果指出，近年來侵臺颱風數目和日降雨強度均有增加的趨勢，雖然受害面積將因農地釋出而不至於大幅增加，但受損金額預期仍將持續增加。由於作物雨害與降雨日數的異常增多有較密切的關係，但降雨日數並未呈現明顯偏多的異常趨勢，因此預期未來雨害受害面積和受損金額仍將持續目前的下降趨勢。旱害與年降雨量和降雨日數的異常偏低(少)，以及日絕對最高溫和≥30℃日數的異常偏高(多)有關，雖然降雨日數並未呈現明顯偏少的趨勢，高溫異常偏高的趨勢也不明顯，但年降雨量異常偏少的可能性增加，因此預期未來旱害的受害面積和受損金額仍將持續目前的上升趨勢。寒害與≤10℃的日數和日絕對最低氣溫的異常偏多(低)有關，受氣候暖化之影響，平地農作物大面積遭受寒害的機率已很低，但山坡地上經濟果樹仍有局部受害的可能，受損金額也不容忽視。因此臺灣地區因異常氣象狀況所導致的嚴重農業氣象災害仍將持續發生，且受損金額有逐年擴大的趨勢。 In this study, yearly data, including number of days ≤10℃ (D10) and ≥30℃ (D30), the lowest (Tmin) and the highest (Tmax) temperatures, accumulated precipitation (Pacc), number of days with precipitation ≥1.0 mm (D1.0mm), and maximum daily rainfall intensity (Irain), from 1949-2003 of 10 Central Weather Bureau (CWB) weather stations distributed around the island and number of typhoon that may invade Taiwan during 1959-2003 were collected. Occurrence of island-wide abnormal meteorological conditions were first identified and followed by 10 year moving average to study the trend. Correlation among severe agrometeorological disasters and those abnormal meteorological conditions were also analyzed. Results indicated that the numbers of typhoon and Irain were increasing recently. Though the acreage of damaged agricultural land was not increased, the economical loss showed a steady increasing trend. The D1.0mm, without significant abnormal changing trend, showed positive correlation with heavy rainfall damage to agriculture production. It is expected that the acreage and economical losses of agricultural production due to heavy rainfall will both follow the current decreasing trend. Drought damages showed negative relationship with Pacc and D1.0 mm, and positive relationship with D30 and Tmax. There was neither significant decreasing trend of D1.0 mm nor increasing trend of Tmax, but Pacc showed significant variation between abnormally high and low. It is expected that the acreage and economical losses of agricultural production due to drought will both follow the current increasing trend. Cold damages showed positive relationships with D10 and Tmin. There was significant warming trend in current years. It is expected that chances of having extensive cold damages over flat land will be rare. However, fruit trees grown on hills suffering significant economical losses due to cold damages may still occurring locally. Thus, severe agrometeorological disasters due to abnormal meteorological conditions will continue to occur and the losses are expected to be expanding.