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[1] Interdecadal variations in the early (May -June) summer monsoon rainfall over South China (SCMR) are found to be related to the ENSO (El Niño/Southern Oscillation) and the PDO (Pacific Decadal Oscillation). An interdecadal variation in SCMR can be identified, with more dry (wet) monsoon years during the periods of high (low) PDO index. Such variations are also related to ENSO in association with PDO. When ENSO and PDO are in phase, i.e. high PDO phase/El Niño events, or low PDO phase/La Niña events, the SCMR tends to be below or above normal respectively more often. But when the ENSO and PDO are out-of-phase, the SCMR has no wet or dry preference. Such relationships appear to be related to the intensity of the subtropical high determined by the superposition of the effects of ENSO and PDO.

ABSTRACT:In this study, we investigate the different impacts of El Niño and El Niño Modoki on China rainfall in their decaying phases. During spring, in the decaying year of El Niño events, there are positive rainfall anomalies south of the Yangtze River, whereas no obvious rainfall signals are found in the same season for the decaying El Niño Modoki. In the subsequent summer season, the wet signal south of the Yangtze River associated with El Niño continues, while suppressed rainfall now appears in the northern Yangtze-Huaihe River region. In contrast, the rainfall is above normal in the region from the Huaihe River to the Yellow River, and below normal in southern China during the summer of the decaying El Niño Modoki events. The distinct China rainfall anomaly is mainly attributed to the difference between the evolution and location of the anomalous western North Pacific (WNP) anti-cyclone associated with El Niño and El Niño Modoki events. For the case of El Niño, the WNP anti-cyclone brings plentiful moisture to southern China; meanwhile it shifts the ridge of sub-tropical high westward in both spring and summer. These tend to induce positive rainfall anomalies in the southern Chinese region. In contrast, due to fast decaying of El Niño Modoki, the anomalous WNP anti-cyclone becomes weak so that there are no significant rainfall anomalies in China. In summer, however, the WNP anti-cyclone re-invigorates possibly associated with a subsequent developing La Niña and extends more northwestward towards the inland region, compared to its El Niño counterpart. The anomalous moisture transport and sub-tropical high activity associated with this WNP anti-cyclone result in different summer rainfall anomalies in China.

In January 2008, central and southern China experienced persistent low temperatures, freezing rain, and snow. The large-scale conditions associated with the occurrence and development of these snowstorms are examined in order to identify the key synoptic controls leading to this event. Three main factors are identified: 1) the persistent blocking high over Siberia, which remained quasi-stationary around 65°E for 3 weeks, led to advection of dry and cold Siberian air down to central and southern China; 2) a strong persistent southwesterly flow associated with the western Pacific subtropical high led to enhanced moisture advection from the Bay of Bengal into central and southern China; and 3) the deep inversion layer in the lower troposphere associated with the extended snow cover over most of central and southern China. The combination of these three factors is likely responsible for the unusual severity of the event, and hence a long return period.

Interannual variations of the East Asian trough (EAT) axis at 500 hPa are studied with the European Centre for Medium-Range Weather Forecasts 40-yr reanalysis data. The associated circulation pattern and pathway of the East Asian winter monsoon (EAWM) with the EAT axis tilt are specially investigated with a trough axis index, which is closely related to the midlatitude baroclinic process and mainly represents the intensity of the eddy-driven jet over the East Asia-North Pacific sector. When the tilt of EAT is smaller than normal, the EAWM prefers to take the southern pathway and less cold air moves to the central North Pacific. However, the EAWM prefers the eastern pathway and brings more cold air to the North Pacific when the tilt of EAT is larger than normal. These differences induce pronounced changes in both the precipitation and the surface air temperature over East and Southeast Asia. Furthermore, the tilt status of the EAT has a significant modulation effect on the regional climate anomalies related to the intensity of the EAWM. The findings suggest an increase in the temperature anomaly associated with the EAWM intensity and a clear northward-southward shift in its pattern in anomalous tilt phase of the EAT. In addition, the modulation tends to be confined mainly to East Asia and expanded to a larger area during the weak and the strong EAWM winters, respectively. The possible reasons for interannual variations of the EAT tilt are discussed, and it is speculated that the midlatitude air-sea interaction in the North Pacific plays a dominant role. This study on the EAT tilt may enrich knowledge of the East Asian winter monsoon beyond the conventional intensity index and may be helpful to improve regional climate prediction in East Asia.

From the point of better biocompatibility and sustainability, biobased shape memory polymers (SMPs) are highly desired. We used 1,3-propanediol, sebacic acid, and itaconic acid, which have been industrially produced via fermentation or extraction with large quantities as the main raw materials for the synthesis of biobased poly(propylene sebacate). Diethylene glycol was used to tailor the flexibility of the polyester. The resulted polyesters were found to be promising SMPs with excellent shape recovery and fixity (near 100% and independent of thermomechanical cycles). The switching temperature and recovery speed of the SMPs are tunable by controlling the composition of the polyesters and their curing extent. The continuously changed switching temperature ranging from 12 to 54 °C was realized. Such temperature range is typical for biomedical applications in the human body. The molecular and crystalline structures were explored to correlate to the shape memory behavior. The combination of potential biocompatibility and biodegradability of the biobased SMPs makes them suitable for fabricating biomedical devices.

This study attempts to assess the possible linkage between Ural–Siberian blocking and the East Asian winter monsoon (EAWM). During the boreal winter, the dominance of blocking thermally enhances cold advection downstream. The frequent occurrence of Ural–Siberian blocking potentially promotes a cold EAWM and vice versa. The seasonal blocking activity can be regarded as the combined effect of the Arctic Oscillation (AO) and the El Niño–Southern Oscillation (ENSO). Weakened (strengthened) meridional flow in the positive (negative) phase of the AO is unfavorable (favorable) for the formation of blocking highs. Because the AO shows a close relationship with the North Atlantic Oscillation (NAO), its teleconnection with Ural–Siberian blocking may exist in the form of an eastward-propagating wave train. Be that as it may, the wave train signal across East Asia may be disturbed by the external effect of a strong ENSO event, which probably enhances (weakens) the westerlies near Siberia in its warm (cold) phase. Consequently, the blocking–EAWM relationship is stronger (weaker) when the AO and ENSO are in phase (out of phase). If both AO and ENSO attain the positive (negative) phase, the Siberian high tends to be weaker (stronger) and the temperature tends to be higher (lower) in East Asia, with less (more) Ural–Siberian blocking. On the other hand, if they are out of phase, they are not strongly linked to the intensity of the Siberian high, and the blocking activity over Ural–Siberia is unclear.