Statistical Downscaling of Summer Temperature Extremes in Northern China

Two approaches of statistical downscaling were applied to indices of temperature extremes based on percentiles of daily maximum and minimum temperature observations at Beijing station in summer during 1960-2008. One was to downscale daily maximum and minimum temperatures by using EOF analysis and stepwise linear regression at first, then to calculate the indices of extremes; the other was to directly downseale the percentile-based indices by using seasonal large-scale temperature and geo-potential height records. The cross-validation results showed that the latter approach has a better performance than the former. Then, the latter approach was applied to 48 meteorological stations in northern China. The cross- validation results for all 48 stations showed close correlation between the percentile-based indices and the seasonal large-scale variables. Finally, future scenarios of indices of temperature extremes in northern China were projected by applying the statistical downsealing to Hadley Centre Coupled Model Version 3 （HadCM3） simulations under the Representative Concentration Pathways 4.5 （RCP 4.5） scenario of the Fifth Coupled Model Inter-comparison Project （CMIP5）. The results showed that the 90th percentile of daily maximum temperatures will increase by about 1.5℃, and the 10th of daily minimum temperatures will increase by about 2℃ during the period 2011- 35 relative to 1980-99.

Observation of Temperature Induced Plasma Frequency Shift in an Extremely Large Magnetoresistance Compound LaSb

We report an optical spectroscopy study on LaSb, a compound recently identified to exhibit extremely large magnetoresistance. Our optieal measurement indicates that the material has a low carrier density. More inter- estingly, the study reveals that the plasma frequency increases with decreasing temperature. This phenomenon suggests either an increase of the conducting carrier density or/and a decrease of the effective mass of carriers with decreasing temperature. We attribute it primarily to the latter effect. Two possible scenarios on its physical origin are examined and discussed. The study offers new insight into the electronic structure of this compound.

Drivers of the Severity of the Extreme Hot Summer of 2015 in Western China

Western China experienced an extreme hot summer in 2015,breaking a number of temperature records.The summer mean surface air temperature(SAT)anomaly was twice the interannual variability.The hottest daytime temperature(TXx)and warmest night-time temperature(TNx)were the highest in China since 1964.This extreme hot summer occurred in the context of steadily increasing temperatures in recent decades.We carried out a set of experiments to evaluate the extent to which the changes in sea surface temperature(SST)/sea ice extent(SIE)and anthropogenic forcing drove the severity of the extreme summer of 2015 in western China.Our results indicate that about 65%–72% of the observed changes in the seasonal mean SAT and the daily maximumand daily minimum(Tmin)temperatures over western China resulted from changes in boundary forcings,including the SST/SIE and anthropogenic forcing.For the relative role of individual forcing,the direct impact of changes in anthropogenic forcing explain about 42% of the SAT warming and 60%(40%)of the increase in TNxand Tmin(TXxand Tmax)in the model response.The changes in SST/SIE contributed to the remaining surface warming and the increase in hot extremes,which are mainly the result of changes in the SST over the Pacific Ocean,where a super El Ni?o event occurred.Our study indicates a prominent role for the direct impact of anthropogenic forcing in the severity of the extreme hot summer in western China in 2015,although the changes in SST/SIE,as well as the internal variability of the atmosphere,also made a contribution.