Heat Wave of the 21st Century

• Main Authors: Yin-Chen Chu, 朱吟晨
• Other Authors: Huang Hsiung Hsu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/67016921996564646978

碩士 === 國立臺灣大學 === 大氣科學研究所 === 95 === The Earth climate has been significantly warming since the late 1970s. No matter what the reason is, it is undoubtedly that the temperature in most of places on the Earth is getting higher. Heat waves, which could result in severe damages and fatality, have become more frequent than the past. This study is aimed to understand the characteristics of the heat waves in 2046-2065 and 2081-2100 based on the IPCC climate change scenario simulations. Before focusing on the future climate, we should first understand the climate in the 20th century. Two methods, based on Huth et al. (2000) and Karl and Knight (1997), were adopted to define “Heat waves”. The former method defines the frequency and duration of heat wave; the latter one defines the intensity. “Heat waves” defined by either method mostly happen in summer. We examined the 16 CWB station datasets in Taiwan, from 1950-2005, and found that there are some evidence indicating the increasing frequency and duration of heat waves. Moreover, the intensity of the warmest 3-day temperature exhibits clear increasing trends in most stations, especially in the cities. “Heat Island Effect” is likely to contribute to this phenomenon. The same two methodologies were applied to study the heat waves in the global domain to validate the simulation results from 10 IPCC AR4 models for the period from 1961 to 2000, and to project the heat wave activity in 2046-2065 and 2081-2100. We explored the spatial characteristics of the change in the heat wave frequency, duration, and the intensity in the future climate under the IPCC A1B scenario. In the 20th century (1961-2000), the diagnostic results based on the NCEP/NCAR Reanalysis indicate that the heat waves occurred most frequently in the middle and high latitude region in both hemispheres. The occurrences of heat waves in the lands near the equator were fewer but lasting longer. Most models show the similar patterns, though the values were not so accurate. The frequencies of heat wave will be doubled in the middle of the 21st century, and become even higher at the end of the 21st century. In addition, the countries near the equator, which are warm in the present time, will encounter more frequent and longer heat wave events in the future time. The evident increases in the highest maximum and minimum temperature show that the intensity of heat wave will significantly increase. Temperature in all land areas will arise 2~4 degree by the end of the 21st century. The characteristics of Heat Wave may be reduced by the change of atmospheric circulation. The geopotential heights in middle and low levels show positive anomalies by the end of the 21st century, especially the subtropics. The anomalies may result a clear skies, weak wind situation, make the high temperature near the surface prolonged. The expansion of Hadley cell may be one of the factors. These results may no represent the true changes that will occur, but will be useful in assessing the possible anthropogenic impact on the future heat wave activity.