Analysis of state of polar vortex in the stratosphere

This poster is devoted to analysis of polar vortex state in the stratosphere. We use the ERA-5 data of daily averages of zonal wind poleward of 60° N at the selected layers from 250 hPa up to 1 hPa in the winter period 1979/80 (October-March). We compute the latitudinal average of longitudinal averages U. Thus we obtain one value per day. It is a very important, because its negative value is one of signs of sudden stratospheric warmings. In each day we made a map of geographical distribution of geopotential height, geographical distribution of grids with easterly wind. For each grid point we compute the vertical difference of zonal wind between adjacent layers: lower layer –upper layer and we consider the following types of differences: Type 1: in both layers the west wind is present, but in the type +1 the west wind is stronger in the lower layer, so this grid increases U, type -1 has weaker wind in lower layer, so it decreases U. Type 2: in both layers the east wind is present, but in the type +2 the east  wind is weaker in the lower layer, so this grid increases U. Type -2 has stronger east  wind in lower layer, so it decreases U. Type 3 has opposite wind direction at adjacent layers in the case of +3 we observe east wind in upper layer and west wind in lower layers –increases U. The opposite is true for -3 type with decreases U. We divided the total difference in zonal wind between adjacent layers into 6 parts. In each part we compute the total sum. We also computed the number of grids in each part and we made a maps of geographical distribution of these points. We compare these sums and we found the largest one for each layer and day and we compare the results between days with positive and negative U