Intraseasonal Oscillation of the South China Sea Summer Monsoon and Its Influence on Regionally Persistent Heavy Rain over Southern China

The intraseasonal oscillation（ISO） in the South China Sea summer monsoon（SCSSM） and its influence on regionally persistent heavy rain（RPHR） over southern China are examined by using satelhte outgoing long wave radiation,NCEP/NCAR reanalysis,and gridded rainfall station data in China from 1981 to 2010.The most important feature of the ISO in SCSSM,contributing to the modulation of RPHR,is found to be the fluctuation in the western Pacific subtropical high（WPSH）,along with a close link to the Madden-Julian oscillation（MJO）.Southern China is divided into three regions by using rotated empirical orthogonal functions（REOFs）for intraseasonal rainfall,where the incidence rate of RPHR is closely linked to the intraseasonal variation in rainfall.It is found that SCSSM ISOs are the key systems controlling the intraseasonal variability in rainfall and can be described by the leading pair of empirical orthogonal functions（EOFs） for the 850-hPa zonal wind over the SCS and southern China.Composite analyses based on the principal components（PCs） of the EOFs indicate that the ISO process in SCSSM exhibits as the east-west oscillation of the WPSH,which is coupled with the northward-propagating MJO,creating alternating dry and wet phases over southern China with a period of 40 days.The wet phases provide stable and lasting circulation conditions that promote RPHR.However,differences in the ISO structures can be found when RPHR occurs in regions where the WPSH assumes different meridional positions.Further examination of the meridional-phase structure suggests an important role of northward-propagating ISO and regional air-sea interaction in the ISO process in SCSSM.

A novel context-aware RPL algorithm based on a triangle module operator

For the use in low-power and lossy networks(LLNs)under complex and harsh communication conditions,the routing protocol for LLNs(RPL)standardized by the Internet Engineering Task Force is specially designed.To improve the performance of LLNs,we propose a novel context-aware RPL algorithm based on a triangle module operator(CAR-TMO).A novel composite context-aware routing metric(CA-RM)is designed,which synchronously evaluates the residual energy index,buffer occupancy ratio of a node,expected transmission count(ETX),delay,and hop count from a candidate parent to the root.CA-RM considers the residual energy index and buffer occupancy ratio of the candidate parent and its preferred parent in a recursive manner to reduce the effect of upstream parents,since farther paths are considered.CA-RM comprehensively uses the sum,mean,and standard deviation values of ETX and delay of links in a path to ensure a better performance.Moreover,in CAR-TMO,the membership function of each routing metric is designed.Then,a comprehensive membership function is constructed based on a triangle module operator,the membership function of each routing metric,and a comprehensive context-aware objective function.A novel mechanism for calculating the node rank and the mechanisms for preferred parent selection are proposed.Finally,theoretical analysis and simulation results show that CAR-TMO outperforms several state-of-the-art RPL algorithms in terms of the packet delivery ratio and energy efficiency.