Analysis Of Energy Budget Characteristics Of The Ural Mountains Blocking High Pressure In Winter

Based on the daily Japanese 55-year Reanalysis dataset,this study analyses the energy budget of 53 blocking high events around the Ural Mountains(UBHs)during the period of winter from 1958 to 2018.The circulation is divided into background flow,low-frequency anomalies and high-frequency eddies.It is found that the low-frequency anomalies absorb energy from the background flow,which makes a great contribution to the maintenance of the UBHs.Specifically,due to the southwestward gradient of the climatological-mean air temperature in the middle and lower troposphere of Eurasia and the southward gradient of the climatological-mean westerlies to the northwest of Lake Baikal in the middle and upper troposphere,it is beneficial for UBHs to absorb the baroclinic energy and barotropic energy from the background flow.Although high-frequency eddies promote the maintenance of UBHs through the conversion of barotropic energy,they also absorb baroclinic energy from UBHs,so the net contribution of high-frequency eddies is negligible.The diabatic heating around the Ural Mountains mainly shows negative anomalies,which is not conducive to the maintenance of local positive temperature anomalies in the middle and lower troposphere,and further inhibits the increase and maintenance of the available potential energy of UBHs,which is not conducive to the maintenance of UBHs.In addition,the advection of kinentic energy leads the evolution of kinentic energy of UBHs,implying the potential role as an indicator of the former for the latter.The contribution from the advection of kinentic energy reduces to much extent if the wave-train like anomalies over the Eurasian continent is considered as a whole.It indicates that the kinetic energy is re-distributed internally over the anomalies over the Eurasian continent.In order to further highlight the characteristics of the energy budget of UBHs,this study also makes a comparative analysis of the characteristics of the energy budget of the blocking highs in the Atlantic.Similar to the UBHs,the blocking highs in the Atlantic Ocean mainly draw baroclinic energy from the background flow,and the diabatic heating is not conducive to the maintenance of its available potential energy.However,the difference of blocking highs between the two places is that there is a southeastward gradient of climatological-mean westerlies in the North Atlantic region,while the southwestward gradient of climatologicalmean westerlies is the main feature in the north of Ural Mountains.Although the shapes of blocking highs of the two places are similar(the extended E-P flux is also similar),when they are superimposed on the above background flow,the opposite results of energy conversion are produced,that is,the blocking highs in the Atlantic convert barotropic energy into the background flow,while the UBHs absorb barotropic energy from the background flow.In addition,because the blocking highs in the Atlantic are located in the exit region of jet stream,the high-frequency eddies are active,which have an obvious net positive contribution to the maintenance of the energy of the blocking highs in the Atlantic,which is obviously different from the characteristic that the high-frequency eddies have no obvious net contribution during the formation of UBHs.