Transcript Slide 1

Extreme Temperatures over East Asia
H. Ito1, N. C. Johnson2, and S.-P. Xie1,2
1UH
a)
Department of Meteorology, 2IPRC
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 2009. 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.