The changes in dynamical tropopause associated with the Euro-Atlantic and West-Asia atmospheric blocking

Abstract

In this study, the anomalies of dynamical tropopause associated with blocking events in wintertime of the period 1959–2020 are analyzed using the JRA-55 re-analysis data with focus on the Southwest Asia. The identification and analysis of blocking properties is based on a wave breaking index. To this end, at first, the periods of occurrence of blocking are identified, and then the anomalies of the tropopause in the upstream and downstream of the relevant blocking locations in the two sectors of West Asia (Aral) and Euro–Atlantic are investigated. The analysis is carried out for the whole blocking events irrespective of their strength and blocking events with the large blocking index. Results show that the general characteristics obtained for blocking, such as location and frequency of occurrence, are in agreement with most previous studies. In addition, with the occurrence of blocking in the above-mentioned sectors, the characteristics of tropopause in the geographical area of blocking occurrence generally undergo well-defined changes. However, in the downstream of the respective atmospheric blockings, corresponding to the Southwest Asia, the changes in the characteristics of tropopause are relatively small. Although the changes are small compared to those in blocking event area itself, but they are expected to have important implications for the evolution of synoptic systems. For both the two sectors, results for the population of events with large blocking index indicate a significant eastward displacement of the location of blocking relative to that of the whole population of blocking events.