Increase of upper troposphere/lower stratosphere wave baroclinicity during the second half of the 20th century 1CESAM, Department of Physics, University of Aveiro, Aveiro, Portugal
2EPhysLab, Faculty of Sciences of Ourense, University of Vigo, Ourense, Spain
3Estación Lidar de Camagüey, Camagüey, Cuba
4Department of Physics, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal
5CGUL, IDL, University of Lisbon, Lisbon, Portugal
Received: 02 July 2009 – Published in Atmos. Chem. Phys. Discuss.: 09 September 2009 Abstract. A strengthening of the equatorward temperature gradient in the upper
troposphere/lower stratosphere (UTLS), at subtropics and
midlatitudes, is consistently reproduced in several modelling
studies of the atmospheric response to the increase of greenhouse
gas radiative forcing. Some of those studies suggest an increase of
the baroclinicity in the UTLS region because of the enhanced
meridional temperature gradient.
Revised: 18 November 2009 – Accepted: 23 November 2009 – Published: 03 December 2009
This study presents observational evidence of an increase of the baroclinic
wave components of UTLS circulation (UTLS wave baroclinicity), during the
second half of the 20th century. The
evidence is given by significant positive trends in the energy of
baroclinic normal modes of the NCEP/NCAR reanalysis,
and significant positive trends in the UTLS eddy available potential energy
of the NCEP/NCAR, ERA-40, NCEP-2 and JRA-25 reanalyses. Significant positive
trends in the frequency of
double tropopause events in radiosonde data are also interpreted as
a manifestation of an increase of the UTLS wave baroclinicity.
Citation: Castanheira, J. M., Añel, J. A., Marques, C. A. F., Antuña, J. C., Liberato, M. L. R., de la Torre, L., and Gimeno, L.: Increase of upper troposphere/lower stratosphere wave baroclinicity during the second half of the 20th century, Atmos. Chem. Phys., 9, 9143-9153, doi:10.5194/acp-9-9143-2009, 2009.