Extensive Cold-Precipitation-Freezing Events in Southern China and Their Circulation Characteristics

Concurrence of low temperature,precipitation and freezing weather in an extensive area would cause devastating impacts on local economy and society.We call such a combination of concurrent disastrous weather“extensive coldprecipitation-freezing”events(ECPFEs).In this study,the ECPFEs in southern China(15°−35°N,102°−123°E)are objectively defined by using daily surface observational data for the period 1951−2013.An ECPFE in southern China is defined if the low temperature area,precipitation area and freezing area concurrently exceed their respective thresholds for at least three consecutive days.The identified ECPFEs are shown to be reasonable and reliable,compared with those in previous studies.The circulation anomalies in ECPFEs are characterized by a large-scale tilted ridge and trough pairing over mid-and high-latitude Eurasia,and the intensified subtropical westerlies along the southern foot of the Tibetan Plateau and the anomalous anticyclonic circulation over the subtropical western Pacific.Comparative analysis reveals that the stable cold air from the north and the warm and moist air from the south converge,facilitating a favorable environment for the concurrence of extensive low-temperature,precipitation and freezing weather.

NOVEL SYNTHESIS OF LONG MULTI-BLOCK HETEROPOLYMER CHAINS WITH AN ORDERED SEQUENCE AND CONTROLLABLE BLOCK LENGTHS

It had very long been a dream in polymer science to synthesize long multi-block polymer chains with an ordered chain sequence and controllable block lengths. Using ionic or living free radical polymerization or furnishing each end of polymer blocks with a reactive functional group, one can only prepare heteropolymer chains with few long blocks, such as diblock and triblock copolymers. The most plausible result so far was a pentablock copolymer. Recently, using a combination of polymer physics and synthetic chemistry, we have invented self-assembly assisted polycondensation (SAAP). This communication reports the results of using this novel method to connect 10-100 triblock polymer chains together to form long multi-block heteropolymer chains with an ordered sequence and controllable block lengths.

Classification of wintertime large-scale tilted ridges over the Eurasian continent and their influences on surface air temperature

本文研究了冬季欧亚大陆大型斜脊系统(LSTR)的类型及其对大范围持续性极端低温事件(EPECE)的影响。结果表明,依据斜脊位置和空间形态,LSTR可分为五类,其中前两类与欧亚大陆EPECE密切相关。第一类LSTR起于乌拉尔山,有利于我国EPECE的发生;第二类LSTR起于科拉半岛,位置偏西,有利于中欧至中西伯利亚一带EPECE的发生。LSTR与西伯利亚高压之间的垂直耦合作用是EPECE发生的重要原因。这些结论对我国EPECE的中期—延伸期预报有一定的指导意义。