image: The probability distribution function of the daily series of Tmax in August over Northeast China before (black line) and after (red line) the interdecadal change. view more
Credit: Ruidan Chen
Against the background of global warming, extreme heat days (EHDs) occur frequently and greatly threaten human health and societal development. Therefore, it is of great importance to understand the variation of EHDs.
Previous studies have indicated that the frequency of EHDs is mainly modulated by the mean state of temperature, and thus the frequency of EHDs mostly presents an increasing trend.
"However, the variability of the daily maximum temperature also plays an important role in the interdecadal change of extreme heat days over Northeast China," says Ms. Liu Wenjun, a Master's student from the group of Dr. Ruidan Chen in the School of Atmospheric Sciences at Sun Yat-sen University and the first author of a paper recently published in Atmospheric and Oceanic Science Letters.
"The variability of the daily maximum temperature in August over Northeast China experienced a significant interdecadal decrease around the early 1990s, which overwhelmed the effect of the mean-state warming and led to an interdecadal decrease in extreme heat days," she explains.
The research team further discovered that the interdecadal change in the variability of daily maximum temperature is modulated by the atmospheric circulation.
"After the early 1990s, the influence of the Silk Road teleconnection and the East Asian-Pacific teleconnection on Northeast China weakened obviously, resulting in a decrease in the variability of the daily maximum temperature over Northeast China," concludes Liu.
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Other contributors to this study include Dr. Ruidan Chen of the School of Atmospheric Sciences at Sun Yat-sen University and Prof. Zhiping Wen of the Department of Atmospheric and Oceanic Sciences at Fudan University.
Journal
Atmospheric and Oceanic Science Letters