1. Extreme Temperatures over East Asia
H. Ito1, N. C. Johnson2, and S.-P. Xie1,2
1UH Department of Meteorology, 2IPRC a) b) c)
The leading summertime (June – August) empirical orthogonal function (EOF) SAT pattern regressed against (a) SAT (color, ᵒC; SAT climatology in contours), (b) precipitation (color, cm/month), (b,c) subseasonal SAT standard deviation (contour, ᵒC), and (c) the sum of warm and cold extreme occurrence (color, days). A positive sum in (c) indicates that the increase in warm extremes exceeds the decrease in cold extremes during the positive phase of the leading EOF.
The interannual variations in the surface air temperature (SAT) patterns (a,d) and number of extreme temperature days (below the 10th and above the 90th percentile) over East Asia were analyzed for summer and winter from 1979 to As mean temperatures increase in summer, the distribution of SAT broadens, indicating a pronounced increase in extreme hot days and a pronounced decrease in extreme cold days (c). In contrast, the winter SAT distribution narrows with increasing temperature, indicating fewer days of extreme temperatures. The increase in extreme summer hot days is attributable to a decrease in precipitation (b) and soil moisture, especially in Mongolia, which results in an increase in the ratio of sensible to latent heat flux. In winter the main SAT pattern is closely related to variations in the Arctic Oscillation. Weaker storms and a northward shift in the storm track result in a pronounced decrease in extreme cold days. d)
Summertime SAT distributions at Ulan Bator, Mongolia for all years (black), years in the positive phase (red), and years in the negative phase (blue) of the leading EOF. The seasonal mean SAT has been subtracted. Triangles show the 10th and 90th SAT percentiles used to define extreme SAT occurrence.