Adaptive Change in Intra-Winter Distribution of Relatively Cold Events to East Asian Warming

Abstract

For the past few decades, daily winter temperatures over East Asia have been higher and less variable. Generally, these simple temperature-distribution shifts should lead to a decrease in the occurrence of cold extremes, but observations of the changes in the extremes are often complicated. In the present study, the change in the occurrence of relatively cold events (daily temperature anomaly, ≤ -2σ for that season) in each winter monsoon over East Asia was examined using ground observations of daily temperature for the period 1954 - 2006. The time-mean temperature for each winter was subtracted to remove the interannual variability and long-term trend. Our analyses reveal that the intraseasonal temperature distribution over East Asia has changed with a negative skew, and the frequency of the relatively cold events has slightly increased (by 0.09 days per decade) over the past few decades, on an average, for the entire analysis domain (east of 105°E, 122 stations). In particular, the increase occurs more dominantly (82% of the total stations) in regions north of 40°N where a stronger warming has progressed. The frequency of relatively cold events is found to be significantly correlated with the variance of the Siberian high and the mean of the Arctic Oscillation. The increasing trend in the frequency of relatively cold events may serve to partly countervail the decrease (-1.12 days per decade) in the frequency of absolute cold events (daily temperature anomaly, ≤ -2σ overall) across the entire observation period.

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