Extreme temperature occurrences over East Asia

Abstract

Extreme daily surface air temperature (SAT; 10th and 90th percentiles) occurrences over East Asia are investigated in relation to seasonal mean and subseasonal variations of SAT as well as to modes of large-scale climate variability, including the Arctic Oscillation, East Asia Winter Monsoon, El Nino Southern Oscillation, and Pacific-Japan teleconnection. Linear regression analysis reveals that seasonal mean shifts of the distribution have a predominant impact on the number of cold and warm extreme days on interannual time scales. Advection of the climatological SAT gradient by anomalous winds is a major mechanism for the winter seasonal mean variability. In contrast, the summer seasonal mean variability is explained by diabatic heating due to downward solar radiation, which is associated with anomalous mid-troposphere circulation that controls total cloud amounts. Advection of SAT by anomalous surface winds is also confirmed for causing anomalies of summer seasonal mean SAT. Regions where extreme occurrences are influenced by the subseasonal SAT variability are extracted by taking the asymmetric component of regression coefficients between the number of cold and warm extreme days. In winter, the subseasonal SAT variability is related to meridional heat transport by transient eddies. In summer, by contrast, it seems to be influenced by both storm activity and precipitation. The frequency distributions of daily SAT anomalies, in relation to modes of climate variability, are generally robust between the reanalysis and station data, in terms of the mean shifts and changes in the standard deviation.