Change in climatic extremes over mainland China based on an integrated extreme climate index

An Integrated Extreme Climatic Index (IECI) is defined for analyzing the overall trend of change in the frequencies of major extreme climatic events over mainland China. The index is composed of 7 individual extreme indicators, i.e. the country-averaged frequencies of high temperature, low temperature, intense precipitation, dust storm and strong wind events, meteorological drought area percentage, and number of land-falling tropical cyclones (TCs). Weights are assigned to the individual country-averaged extreme indices based on the mean economic losses and casualties induced by the extreme events in the last 5 yr. The IECI is then defined as the weighted sums of the standardized individual extreme climatic indices. During the past 54 yr (1956–2009), the IECI has shown no significant change in terms of linear trend, although inter-annual and inter-decadal variations are evident, with lower values and a decreasing trend occurring from the late 1950s to the early 1980s, and higher values and an increasing trend since the mid-1980s. In view of the individual extreme climatic indices, significant upward trends were detected for frequencies of high temperature events and the percentage of meteorological drought areas, and significant downward trends were found for frequencies of low temperature, dust storms, and strong wind events. The number of land-falling TCs is in an insignificant decline, and no significant trend was found for frequency of intense precipitation events. Our analysis revealed that the frequencies of major extreme climatic events with the potential to cause severe meteorological disasters in mainland China show more complicated changes during the period of accelerated climate warming.