1950年代東亞氣候突變

An analysis of abrupt climate change around 1950's

羅資婷(Tzu-Ting Lo)

指導教授 ： 許晃雄

國立臺灣大學/理學院/大氣科學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01155

摘要

突變(abrupt change)是指一個維持五到十年以上的環流場突然有大規模的改變，跳躍到另一個穩定環流場的狀態。本研究以1950年代初期台灣夏季氣溫的突變為出發點，探討突變的區域以及可能造成突變發生的原因。

首先，為了確立50年代初期的突變是否存在於全球，使用了Yasunaka(2002)提出的方法，發現除了氣溫以外，海溫及氣壓的全球性突變並不顯著。雖然突變不是全球性，但在美洲、非洲、印度附近等地亦可以發現在50年代初期有突變現象。另外，針對區域性突變來看，使用Yonetani(1992)提出之方法，發現東亞區域(90-140E,20-50N)有明顯的突變，並得到環流場的分佈變化。在50年代過後，東亞大陸上氣溫下降，台灣附近海面一直到黑潮延伸區域為海溫上升的趨勢，在氣壓方面，東亞區域在50年代過後有氣壓上升的結果。由環流變化場亦可發現，台灣附近季風槽減弱，且海陸溫差降低，可間接推論50年代過後季風有減弱的趨勢。

探討造成50年代突變的原因，考慮到50年代與PDO(Pacific Decadal Oscillation)相位變化的年份1947年很相近，且黑潮延伸地帶的海溫升高與PDO cold phase相近的因素，因而加以討論50年代東亞地區的突變與PDO兩者之間的關係。參考Latif and Barnett(1994,1996)、Deser(1996,1999)以及Qiu(2003)提出有關PDO delay效應影響黑潮延伸區域溫度的三種機制，我們試著將50年代初期過後的溫度變化與氣壓場的變化配合在一起，發現黑潮延伸區域(Kuroshio extention)在50年代過後增暖，且北方高壓增強，decadal海溫的移動變化從1947年過後先往西再往南移動，為逆轉現象，也就是說在1947年PDO 的相位發生改變過後，中北太平洋海溫增暖，暖水將會隨著時間往西且往南傳遞，使黑潮延伸區域及其南方海面增暖的時間有4-5年的延遲變化(delay)。考慮上述種種分析的結果，發現50年代突變的環流場與其演進情形與Deser理論相近，推測1950年代初期突變的原因，有可能為PDO在1947年造成的中北太平洋增暖現象，經羅士比波(Rossby wave)調整造成4-5年的delay，造成1950年代初期整個東亞區域突變的發生。

關鍵字

突變 ； 太平洋年代振盪

並列摘要

Abrupt change is characterized by a significant change between the two steady states, continuing more than 5 years. In the present study, we have a start to investigate the 1950’s abrupt change of Taiwan, and research the area of abrupt change and how it happened.

First, by the approach of Yasunaka, we find that the global suddenly change of 1950’s is obvious in temperature but not in sea surface temperature and sea level pressure. Even though that, we still find some place with the shift, like America, Africa and India. Then, we use the method of Yonetani (1992) to detect regional abrupt change, and find an apparent one in east-asia (90°-140°E, 20°-50°N). After regime shift, temperature decreased in most eastern asia, and increased in coast of eastern asia, especially in Kuroshio extension. There was also a tendency that the pressure increased as a whole. Because circulation changed like above, monsoon though which was near Taiwan weakened and temperature difference decreased, monsoon was inferred to descend after 1950’s.

The reason caused abrupt change is discussed. Because the time of abrupt change was close to transition of PDO and the warmth of kuroshio extention was very similar to cold phase of PDO, we try to find the relationship between the abrupt change and Pacific Decadal Oscillation (PDO). To compare the delay viewpoints of Latif et al. (1996)、Deser(1999) and Bo Qiu (2003), we match up the variation of temperature and pressure. Some information searched out that kuroshio extention warmed, with anticyclone on its north, and decadal change of sea surface temperature moved westly then southly after 1947, the transition of PDO. So kuroshio extention and the southern part warmed after 4-5 years, because the reason of delay. Thinking of a point of view above, we consider the 1950’s abrupt change is similar to Deser(1999). So we infer the reason which make the abrupt change happened in east-asia is the delay of PDO, adjusted by rossby wave through 4-5 years.

並列關鍵字

delay ； abrupt change ； PDO

參考文獻

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