Sub-Seasonal Scale Oscillations Of Winter Temperature In China And The Relationship With Interannual Anomaly

The study of winter temperature anomaly in China often focuses on the interannual and interdecadal variation and related influencing factors.There are many researches on the characteristics of intraseasonal oscillation,while few studies on the influence of interaction between sub-seasonal and other scales on winter temperature anomaly.Therefore,based on the daily observed and reanalysis data for the period from 1959 to 2011,the structure and evolution characteristics of sub-seasonal oscillation of winter temperature in China are studied.The temperature equations are used to diagnose the impact of different scale interactions on the interannual variation of winter temperature,and the role of interactions associated with sub seasonal in interannual anomalies of winter temperatures was discussed.The results showed that:(1)There are regional differences in the sub seasonal oscillation of winter temperatures in China.The sub-seasonal temperatures in southern,western and eastern have 10-20d and 2060d oscillation,but the 10-20d oscillation in southern and eastern region are more pronounced than western region.The oscillation intensity of 10-90d?10-20d and 20-60d in winter has obvious interannual variation.(2)Sub-seasonal oscillation was pronounced in South China?Northwest?North China and Northeast.The sub-seasonal oscillation intensity in the key area(38-53 ° N,118-133 ° E)shows significant negative correlation with winter temperature anomaly.(3)There is a significant 10-32d oscillation period over the key region in cold winters and at the 38 days reaches first peak in warm winters.The power spectrum is greater in cold winters.Sub-seasonal temperature and 300hPa geopotential height both shifted to southeast in cold(warm)winters,the relationship between low-level sub-seasonal temperature and uppertropospheric geopotential height is contacted through hydrostatic relationship.The 300hPa wave activity flux reveals that wave energy eastward and southeastward propagation,indicating that Rossby wave energy dispersion is the main source of upper-tropospheric geopotential height propagation.(4)Typical cold(warm)winters have obvious negative(positive)NAO structure.The anomalous geopotential height present positive(negative)-negative(positive)positive(negative)-negative(positive)structure from the northern Atlantic?Europe?the Ural Mountains and northern China,and key region has obvious baroclinic structural features.The vertical wind shear caused by meridional temperature gradient in cold and warm winters,and the 200hPa westerly jet located at the south of key region,leading to significant disturbance and unstable energy.Moreover,the vertical wind shear and 200hPa jet are stronger in cold winters hence unstable energy and the sub-seasonal oscillation are stronger.(5)The interannual variation of winter temperature is dominated by the climatological mean and interannual timescale interactions.The sum of the contributions associated with the sub-seasonal accounted for 22.3%(10%)of the largest contribution(temperature advection composed of the climatological mean temperature and interannual timescale wind)in cold(warm)winters.Although the contribution relatively small,while has an important positive contribution to winter temperature anomaly.The key region shows cold(warm)temperature advection composed of the climatological mean temperature and the interannual wind-?(?)]and the climatological mean wind and interannual temperature-?[(?)in cold(warm)winters.The 1000hPa climatological mean atmospheric stability parameter and the interannual vertical velocity was negative(positive)adiabatic heating in cold(warm)winters,which provided a positive contribution to winter temperature anomaly.