| Based on the ERA5 daily reanalysis dataset provided by the European Centre for Medium-Range Weather Forecasts(ECMWF),this study focuses on the occurrence and development of the Ural blocking high(UB)in winter during the period from 1979 to 2019,and analyzes the connections between the establishment and maintenance processes and the geopotential height anomaly at different time scales by using power spectrum analysis,correlation analysis,synthetic analysis and other statistical methods.On this basis,the heat and momentum characteristics of the long-lasting blocking high events are explored,and finally analyze the influence of the atmospheric intra-seasonal oscillation on the interdecadal variation of the Ural blockings in winter.The main conclusions are as follows:(1)114 Ural blocking high events occurred during the winter of 1979/1980 to 2019/2020,and the geopotential height in the Ural Mountains exhibited significant intra-seasonal oscillations.The multi-scale analysis revealed that the establishment of the Ural blockings mainly depends on the 10～20 days geopotential height anomaly,and the maintenance depends on the 20～80 days geopotential height anomaly.During the establishment and maintenance processes of blockings,the quasi-biweekly geopotential height anomaly exhibited eastward propagation.(2)Dividing the blocking high events into two categories,both continuous blocking high events(the interval between the two adjacent blockings is less than or equal to 6 days)and longlasting blocking high events(the blocking high is maintained for 10 days or greater)were established and maintained with intra-seasonal scale(20～80 days)geopotential height anomaly,with the difference that the quasi-biweekly geopotential height anomaly in continuous blocking high events had a westward propagation signal,while the 10～20 days component of geopotential height anomaly in long-lasting blocking high events exhibited a southeastward propagation,and the 20～80 days component exhibited only a southward propagation.(3)Heat and momentum transport had an important influence on the maintenance of longlasting blockings,where intra-seasonal scale heat fluxes allowed heat to accumulate in the Ural Mountains,meanwhile the momentum was transported to the pole,provided favorable conditions for the long time maintained of blockings.In the developmental stage of the longlasting blockings,the quasi-biweekly scale and intra-seasonal scale stationary heat flux gradients played a common role,while the momentum transport was dominated by the intraseasonal oscillation of stationary momentum flux,which promoted the establishment and development of the long-lasting block high events.(4)The winter Ural blocking high events showed significant interdecadal variation characteristics in recent 41 years.The blockings were less in 1988/1989 to 2001/2002,and more in 2002/2003 to 2019/2020,corresponding to the opposite distribution of 500 hPa geopotential height anomaly field,temperature anomaly field and wind anomaly field.The strong intensity of the 20～80 days variability of the geopotential height often caused more blocking high events. |
