Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere 1Depto. de Geofísica y Meteorología, Universidad Complutense de Madrid, Madrid, Spain
04 Dec 2012
2National Center for Atmospheric Research, Boulder, Colorado, USA
Received: 12 Jul 2012 – Published in Atmos. Chem. Phys. Discuss.: 31 Jul 2012Abstract. Temporal variability of the upwelling near the tropical tropopause on daily
to annual timescales is investigated using three different estimates computed
from the ERA-Interim reanalysis. These include upwelling archived by the
reanalysis, plus estimates derived from thermodynamic and momentum balance
calculations. Substantial variability in upwelling is observed on both
seasonal and sub-seasonal timescales, and the three estimates show reasonably
good agreement. Tropical upwelling should exert strong influence on
temperatures and on tracers with large vertical gradients in the lower
stratosphere. We test this behavior by comparing the calculated upwelling
estimates with observed temperatures in the tropical lower stratosphere, and
with measurements of ozone and carbon monoxide (CO) from the Aura Microwave
Limb Sounder (MLS) satellite instrument. Time series of temperature, ozone
and CO are well correlated in the tropical lower stratosphere, and we
quantify the influence of tropical upwelling on this joint variability.
Strong coherent annual cycles observed in each quantity are found to reflect
the seasonal cycle in upwelling. Statistically significant correlations
between upwelling, temperatures and tracers are also found for sub-seasonal
timescales, demonstrating the importance of upwelling in forcing transient
variability in the lower tropical stratosphere.
Revised: 12 Oct 2012 – Accepted: 19 Nov 2012 – Published: 04 Dec 2012
Citation: Abalos, M., Randel, W. J., and Serrano, E.: Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere, Atmos. Chem. Phys., 12, 11505-11517, doi:10.5194/acp-12-11505-2012, 2012.