Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 793-806, 2017
https://doi.org/10.5194/acp-17-793-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
18 Jan 2017
Tropical temperature variability and Kelvin-wave activity in the UTLS from GPS RO measurements
Barbara Scherllin-Pirscher1,2, William J. Randel3, and Joowan Kim3,4 1Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics (IGAM/IP), University of Graz, Graz, Austria
2Zentralanstalt für Meteorologie und Geodynamik (ZAMG), Vienna, Austria
3National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA
4Department of Atmospheric Sciences, Kongju National University, Gongju, Korea
Abstract. Tropical temperature variability over 10–30 km and associated Kelvin-wave activity are investigated using GPS radio occultation (RO) data from January 2002 to December 2014. RO data are a powerful tool for quantifying tropical temperature oscillations with short vertical wavelengths due to their high vertical resolution and high accuracy and precision. Gridded temperatures from GPS RO show the strongest variability in the tropical tropopause region (on average 3 K2). Large-scale zonal variability is dominated by transient sub-seasonal waves (2 K2), and about half of sub-seasonal variance is explained by eastward-traveling Kelvin waves with periods of 4 to 30 days (1 K2). Quasi-stationary waves associated with the annual cycle and interannual variability contribute about a third (1 K2) to total resolved zonal variance. Sub-seasonal waves, including Kelvin waves, are highly transient in time. Above 20 km, Kelvin waves are strongly modulated by the quasi-biennial oscillation (QBO) in stratospheric zonal winds, with enhanced wave activity during the westerly shear phase of the QBO. In the tropical tropopause region, however, peaks of Kelvin-wave activity are irregularly distributed in time. Several peaks coincide with maxima of zonal variance in tropospheric deep convection, but other episodes are not evidently related. Further investigations of convective forcing and atmospheric background conditions are needed to better understand variability near the tropopause.

Citation: Scherllin-Pirscher, B., Randel, W. J., and Kim, J.: Tropical temperature variability and Kelvin-wave activity in the UTLS from GPS RO measurements, Atmos. Chem. Phys., 17, 793-806, https://doi.org/10.5194/acp-17-793-2017, 2017.
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Short summary
Tropical temperature variability and associated Kelvin-wave activity are investigated from 10 km to 30 km using 13 years of high-resolution observational data. Strongest temperature variability is found in the tropical tropopause region between about 16 km and 20 km, where peaks of Kelvin-wave activity are irregularly distributed in time. Detailed knowledge of dynamical processes in the tropical tropopause region is an essential part of better understanding climate variability and change.
Tropical temperature variability and associated Kelvin-wave activity are investigated from 10 km...
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