11 Jul 2023
 | 11 Jul 2023

QBO modulation of the Asian Monsoon water vapour

Cristina Peña-Ortiz, Nurial Pilar Plaza, David Gallego, and Felix Plöger

Abstract. The Asian Monsoon (AM) plays a key role in the transport of water vapour to the lower stratosphere and contributes significantly to the wet phase of the annual global stratospheric water vapour cycle. Although it is known that the QBO is one of the main drivers of the interannual variability of the AM water vapour, the physical mechanisms responsible for this variability remain unclear. Here we have used daily MLS data for the period 2005–2020 to characterize the QBO signature on the lower stratosphere AM water vapour during the boreal summer. We show that the QBO has the strongest impact during August, when QBO-W minus QBO-E differences may reach 1 ppmv at 100 hPa, although a significant signature is also observed during July. We find that the region whose temperature controls the QBO signal on water vapour over the AM differs between July and August. In July, when the key region is over the tropical Indian Ocean, the QBO modulation of the AM water vapour occurs in phase with the signal over the equator whereas in August, when the key region is at the subtropics, over the southwestern flank of the Monsoon, the signal over the AM is opposite to that over the equator. Our results reveal that the QBO signal on the temperature on the south side of the anticyclone, which ultimately has an impact on AM water vapour, is, in turn, modulated by the QBO impact on convection. Thus, we find that the QBO signature on convection over the equator gives rise to Rossby waves trains that produce variations in convection over the southern side of the AM anticyclone such that weaker convection over this region generates an increase in water vapour and vice versa.

Cristina Peña-Ortiz et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1432', Anonymous Referee #1, 07 Aug 2023
    • AC1: 'Reply on RC1', Cristina Peña-Ortiz, 29 Nov 2023
  • RC2: 'Comment on egusphere-2023-1432', Anonymous Referee #2, 03 Oct 2023
    • AC2: 'Reply on RC2', Cristina Peña-Ortiz, 29 Nov 2023

Cristina Peña-Ortiz et al.

Cristina Peña-Ortiz et al.


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Short summary
Although water vapour (H2O) in the lower stratosphere is only a few molecules among 1 million air molecules, atmospheric radiative forcing and surface temperature are particularly sensible to small changes in its concentration. Monsoon regions play a key role in H2O transport and in its concentration in the lower stratosphere. We show how the QBO has a major impact on H2O over the Asian monsoon during August through changes in temperature caused by the QBO modulation of convection.