Features of the EAP events on the medium-range evolution process and the mid- and high-latitude Rossby wave activities during the Meiyu period

In this paper, features for the evolution of the East Asia/Pacific （EAP） events and their association with high- and mid-latitude Rossby waves during the Meiyu period are analyzed on the medium-range time scale, it is shown that life cycles of the positive and negative EAP events cannot be simply regarded as ＂mirror＂ each other. In the upper troposphere, downward propagations of Rossby wave packets both over high- and mid-latitude regions of Eurasian continent and over the Asian jet region are responsible for generating basic patterns of high- and mid-latitude anomaly centers of the events. In this layer, Rossby wave packets also propagate from the mid-latitude anomaly center to the high-latitude one. In the middle and lower troposphere, the formation of the subtropical anomaly center of the event is mainly attributed to the anomalous convective activity in the tropical Pacific warm pool. The northward Rossby wave energy dispersion from this center is favorable to the enhancement and maintenance of the mid-latitude anomaly center in the same layer. Finally, it might be hypothesized that typical features of the positive and negative EAP events in their mature phase result from the interaction between （or phase-locking of） respective anomalous circulations induced both by quasi-zonal Rossby wave packets embedded in upper troposphere westerly and by quasi-meridional Rossby wave packets in the background flow of the East Asian summer monsoon in the middle and lower troposphere.     

Anomalous activity of East Asian winter monsoon and the tropical Pacific SSTA

The relationship between the anomalous East Asian winter monsoon (EAWM) activity and the tropical Pacific SST anomalies has been identified using the results of 40-year integration of the IAP CGCM1 model and 10-year observational data. In the strong EAWM year, the western and central Pacific are dominated by positive SST anomalies while the eastern Pacific is negative ones. In the weak EAWM year, the SSTA pattern is quite different and shows El Nino-like SST anomalies. The strong EAWM activity tends to create extra easterly flow to the east and extra westerly flow to the west of the warm SSTA region over the equatorial western and central Pacific, thus leading to the enhancement of convergence and convection of the flow in this region and favorable to the maintenance and development of such an SSTA pattern. On the other hand, the warm SST anomaly over the western and central Pacific, as a forcing, may lead to a specific pattern of the northern extratropical atmosphere, which is favorable to the strong EAWM activity. The tropical Pacific SSTA pattern related closely to the strong EAWM activity differs significantly from that of the La Nina year.     

Wintertime extreme precipitation event over southern Chinaand its typical circulation features

This study objectively defined an extremeprecipitation event （EPE） over southern China and inves-tigated the associated typical circulation pattern on theintraseasonal time scale. The occurrence of the EPEresulted from the joint operations of anomalous circula-tions over the subtropics and mid-high latitudes. During theEPE, simultaneous enhancements of the trough over theBay of Bengal （BBT） and the Western Pacific subtropicalhigh （WPSH） facilitated thetions over southern China,abundant water vapor condi-whereas the weakened EastAsian major trough （EAT） led to a moderate cold airinvasion to that region, producing a persistent convergencezone over southern China. Wave train pattern in NorthAtlantic and Europe may be viewed as precursory signalsfor the EPE over southern China, and it contributed to theRossby wave propagation in association with the EPE.These wave packets propagated toward East Asia mainlyalong the North African-Asian subtropical westerly jetwaveguide. Low-frequency disturbances along this wave-guide contributed to the enhancement of the BBT andWPSH and the weakening of the EAT, constitutingfavorable circulation conditions for the EPE.     

Simulation of the future change of East Asian monsoon climate using the IPCC SRES A2 and B2 scenarios

In this paper, we applied the newest emission scenarios of the sulfur and greenhouse gases, i.e. Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 and B2 scenarios, to investigating the change of the East Asian climate in the last three decades of the 21st century with an atmosphere-ocean coupled general circulation model. The global warming enlarges the land-sea thermal contrast and, hence, enhances (reduces) the East Asian summer (winter) monsoon circulation. The precipitation from the Yangtze and Huaihe river valley to North China increases significantly. In particular, the strong rainfall increase over North China implies that the East Asian rainy area would expand northward. In addition, from the southeastern coastal area to North China, the rainfall would increase significantly in September, implying that the rainy period of the East Asian monsoon would be prolonged about one month. In July, August and September, the interannual variability of the precipitation enhances evidently over North China, meaning a risk of flooding in the future.