Figure 1

(a) JJA mean CRU precipitation EOF1 mode (PC1) during 1901–2009; (b) the standardized time series of PC1 (black) and its nine-year running mean value (red); (c) regression of JJA mean 700-hPa flow of the twentieth century reanalysis V2 products against the PC1 during 1901–2009, in which the grey shaded area is for topography; (d) the standardized time series of JJA mean precipitation over Asia (the red solid line) and North America (115°W-95°W, 35°N-45°N; the black solid line) during 1901–2009 and their nine-year running means (dashed lines); (e) regression of AMJJA mean CRU surface air temperature against the PC1 during 1901–2009, in which two boxes indicate the subtropical and midlatitude Eurasia and the mid- and high-latitude North America, respectively; and (f) same as in (e) but for HadISST SST, in which the box indicates the equatorial central-eastern Pacific. These figures are generated by Grid Analysis and Display System (GrADS) Version 2.0.1.oga.1 with Copyright (c) 1988–2011 by Brian Doty and the Institute for Global Environment and Society (IGES) (ftp://cola.gmu.edu/grads/2.0/old/).