Volume 80 (2002) Issue 6 Pages 1309-1324
From analyses based on Singular Value Decomposition of rainfall and 500 hPa geopotential height anomalies, we have identified two atmospheric teleconnection pattern linking interannual variability of summertime precipitation over East Asia and the continental United States. The first pattern is associated with enhanced rainfall over the Yangtze River region to above-normal rainfall over the US northern Great Plains and the Midwest, and reduced rainfall over the Atlantic coast. It features zonally elongated 500 hPa height anomalies over the subtropical and extratropical western North Pacific coupled to a regional circulation pattern over North American that regulates moisture transport from the Gulf of Mexico to the Northern Great Plains. The second pattern shows enhanced rainfall anomalies over the Huaihe River, northeastern and southern China and deficient rainfall over the central US. It connects the East Asian and North American continents via a pan-Pacific wavetrain signal, possibly stemming from Rossby wave dispersion from fluctuations of large-scale heat sources, and sinks in the Indo-Pacific region. Examination of associated sea surface temperature variability in the North Pacific suggests that the first pattern may be influenced by El Niño in the preceding spring, but becomes increasing decoupled from tropical SST during the summer and fall. However, the second pattern has no significant relationship with El Niño.
Analysis of extreme rainfall statistics between regions in East Asia and North America suggests that occurrence of the aforementioned teleconnection patterns is associated with increased probability for extreme rainfall events over the Yangtze River Valley, coupled to increased probability of anomalies of the same sign over the US Midwest, and of the opposite sign over the US Mid-Atlantic coast. Our results suggest that the summertime teleconnection patterns should be further explored for additional sources of potential predictability of summertime floods or droughts over regions of East Asia and North America.