Interannual variations of temperature and vertical motion at the tropical tropopause associated with ENSO

Abstract

Interannual variations of tropopause temperature and vertical p-velocity around the tropical tropopause are investigated. Observations show the tropopause temperature (altitude) is higher (lower) over the east side of maritime continent and lower (higher) over the equatorial eastern Pacific during El Niño compared with La Niña. As for the QBO, the tropopause temperature (altitude) is higher (lower) in all longitudes in the westerly phase. A multiple regression analysis shows the combined effect of ENSO and QBO can explain 25 - 50% of the interannual variation. An AGCM simulation agrees with the observation for the ENSO signal. The simulation supports the existence of the stratospheric drain over the maritime continent in the tropopause region and indicates a zonal shift of the upward (downward) motion below (above) the tropopause with ENSO.