Role of Quasi-Biennial oscillation on the link between sudden stratospheric warming and tropical weather events

Abstract

This paper illustrates the modulation of meteorological parameters over the tropics in the east and west phases of the quasi-biennial oscillation (QBO) during the sudden stratospheric warming (SSW). Twenty years composite of SSW episodes have been analysed, and the results show a teleconnection between northern polar SSW and changes in meteorological parameters throughout tropical troposphere to stratosphere during both the phases of QBO. The tropical troposphere shows different temperature pattern in the two opposite phases of QBO during polar SSW. The lower tropospheric temperature decreases about five days prior to the onset day, persisting as such as for about five days post-onset day, and increases rapidly during the east phase whereas a sudden dip in temperature is observed in the west phase. The easterly wind at the upper tropospheric region is observed to be coupled to the easterly wind in the QBO core region of stratosphere during the easterly phase of QBO whereas they are decoupled in the westerly phase. Prior to the peak polar warming, a strong convective cell develops over the southern hemispheric tropics, and a convective cell develops over northern hemisphere during the peak warming period. This study indicates that during the easterly QBO-SSW period, increasing tropopause easterly wind causes tropopause cooling due to easterly wind's coupling with the QBO core region around the onset day of SSW. As a result, the changes in the tropopause strengthen the Hadley cell circulation thus enhancing the convective activity over the tropical region associated with northern polar SSW. Contrary to the prior knowledge of convection being centred mostly along 5°S–10°S, it is found that other convection band located at around 10°N also produces rainfall in the tropical region.