Projects
VABES: Variability of the Lower Stratosphere Water Vapor
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Stratospheric water vapor plays a major role in chemical and radiative processes of the stratosphere and, over
the last decade, it has also been acknowledged as a determining factor of the global climate. Its concentration
has significantly risen over the second half of the 20th century. Although the reason for this trend remains
unknown, it might explain up to a 30% of the observed surface warming. This trend abruptly shifted in 2001, which
could have contributed to the observed global warming hiatus.
It is in the lower stratosphere where vapor variability has the greatest impact on climate. In this layer, water
vapor depends almost exclusively on transport from the troposphere and the Asian and North American monsoons are
major sources. These monsoonal regions are the main sources of Northern Hemisphere water vapor and contribute
significantly to the wet phase of the stratospheric annual cycle. However, despite its importance, the mechanism
of this transport remains unknown. Particularly, there is much uncertainty about the different roles of deep
convection, large scale circulation or in situ dehydration. On the other hand, lower stratosphere water vapor over
Asian and North American monsoons shows an interannual variability dominated by the Quasi Biennial Oscillation (QBO)
and El Niño Southern Oscillation (ENSO). However, the mechanisms causing this variability have been poorly
investigated and our knowledge about then is very limited.
It has been neither analyzed stratospheric water vapor trends over these regions nor the contribution of the
monsoons to the observed trend over the last decades. This proposal aims the study of the lower stratosphere water vapor variability over these monsoonal regions, the
characterization of its modulation by the QBO and ENSO and the relation of these climate patterns with water vapor
transport through the monsoons.
Finally, we seek to evaluate the impact of green house gases emissions on the transport and concentration of water
vapor over these regions. In order to achieve these objectives we will make use of reanalysis and CMIP5 models data
and will apply a Lagrangian transport and dispersion model (FLEXPART). As far as we are concerned no other group
has applied Lagrangian methodologies for the study of the interannual variability of water vapor transport through
the monsoons.
Key words: Water vapor, stratosphere, monsoon, QBO, ENSO, FLEXPART, CMIP5 models
Research funded by the Spanish Ministry of Economy and Competitiveness through the project CGL2016-78562-P
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