Figure 3: Northern boundary of the East Asian summer (JJA) monsoon circulation and meridional distribution of mean summer rainfall during the 5 geological periods.

(a) Northern limits of the East Asian monsoon overlaid on the 850 hPa streamline field of PD. (b) summer rainfall rates (mm day−1) averaged over 105°–120°E. The corresponding ages are labeled for each period in both (a) and (b). Longitudes 105°–120°E cover the conventional range of the present-day East Asian monsoon region. Maps were created using GrADS (Version 1.9b4, http://cola.gmu.edu/grads/).