Relationship between Temperature Variation in Winter of China and Arctic Oscillation

[Objective] The study aimed to discuss the relationship between temperature variation in winter of China and arctic oscillation. [Method] By using the NCEP/NCAR reanalysis data, AO index series and monthly temperature data from 160 stations of China, the variation characteris- tics of temperature in winter and AO index series as well as their relationship from 1951 to 2007 were studied. [Result] Temperature in winter of Chi- na correlated positively with AO index series. Both arctic oscillation and winter temperature in China had two major periods of 8 and 18 years. ⅠWTr and ⅠAO series, which had obvious inter-annual and inter-decadal variations, presented the almost same rising trend and had close relationship on an inter-decadal scale. Compared with AO, the Siberia high had more distinguished influences on inter-annual variations of temperature in winter of China. AO might affect changes in the Siberian high and thereby influence temperature in winter of China. AO had a greater influence on tempera- ture in winter of China than the Siberia high on an inter-decadal scale. When the East Asian through was weak, temperature in winter of China and AO index were low, while they were high as it was strong. The impact of AO index on an inter-decadal scale was more significant than the impact on an inter-annual scale. [ Condusien] The research could make the effects of AO on winter temperature of China clear.

Mechanism and effects of the increase in winter temperatures in the Arctic region on cold winters in Heilongjiang Province,Northeast China for the period 1961-2018

With the advent of climate change,winter temperatures have been steadily increasing in the middle-to-high latitudes of the world.However,we have not found a corresponding decrease in the number of extremely cold winters.This paper,based on Climatic Research Unit(CRU)re-analysis data,and methods of trend analysis,mutation analysis,correlation analysis,reports on the effects of Arctic warming on winter temperatures in Heilongjiang Province,Northeast China.The results show that:(1)during the period 1961-2018,winter temperatures in the Arctic increased considerably,that is,3.5 times those of the Equator,which has led to an increasing temperature gradient between the Arctic and the Equator.An abrupt change in winter temperatures in the Arctic was observed in 2000.(2)Due to the global warming,an extremely significant warming occurred in Heilongjiang in winter,in particular,after the Arctic mutation in 2000,although there were two warm winters,more cold winters were observed and the interannual variability of winter temperature also increased.(3)Affected by the warming trend in the Arctic,the Siberian High has intensified,and both the Arctic Vortex and the Eurasian Zonal Circulation Index has weakened.This explains the decrease in winter temperatures in Heilongjiang,and why cold winters still dominate.Moreover,the increase in temperature difference between the Arctic and the Equator is another reason for the decrease in winter temperatures in Heilongjiang.

Bias Analysis and Correction of Ground Surface Temperature Observations across China

Based on the ground surface temperature(GST)and snow surface temperature(SST)measurements during the period of adjustment from manual to automatic observation systems in China,the influence of observation methods on GST and its relationship with snow cover is analyzed.GST is corrected by SST,and the correction effect is evaluated.The results show that,during the parallel observation period,the winter GSTs from automatic observations are generally higher than those from manual observations,with the automatically observed national daily GST 1.18°C higher.The adjustment has a greater impact on GSTs at 0200,0800,and 2000 Beijing Time(BT)than at 1400 BT,and it has the greatest impact in Northeast and Northwest China,with deviations of 5.24 and 2.09°C,respectively.The GST deviation is closely related to the snow depth and annual snow totals.The average daily GST deviation increases at the rate of 0.66°C per 1-cm increase of snow depth when it is<15 cm,while it tends to be stable at around 10°C for snow depth over 15 cm.The GST deviation at a station is affected by its winter snow totals in Northeast and Northwest China,where the largest deviations are found where snow totals are all above 1000 cm.After the correction with SST,the mean deviation between the automatic and manual observations as well as the false trend can be effectively reduced.Following the correction,the mean deviation of daily GST decreases by 5.8°C,and its trend decreases from 1.87 to 0.65°C decade-1.