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Project name:

DYNOCC – El Niño Dynamics and Effects Observed with Radio Occultation

Project leader:

Barbara Scherllin-Pirscher

Projekt team:

Barbara Scherllin-Pirscher
Andrea K. Steiner


L. Haimberger, Dep. of Meteorology and Geophysics, Univ. of Vienna, Austria

W. J. Randel, National Center for Atmospheric Research (NCAR) and University Corporation for Atmospheric Research (UCAR), Boulder, CO, USA

S. S. Leroy, Anderson Group, Harvard University, Cambridge, MA, USA


Hertha Firnberg-Position, FWF – Austrian Science Fund




El Niño Southern Oscillation (ENSO) is a coupled ocean-atmosphere phenomenon, which links sea surface temperature (SST) and ocean heat content to atmospheric dynamics. ENSO is the most significant mode of interannual climate variability of the tropical troposphere. Variations of convection, atmospheric temperature and circulation are strongly pronounced at tropospheric low latitudes but signatures associated with ENSO have also been observed at high latitudes as well as at stratospheric altitudes. Numerous studies over the last decades have analyzed the influence of ENSO on atmospheric temperature using observational data, e.g., from radiosondes or satellites, reanalyses, or model data. Since traditional observations have limited spatial coverage and most satellite data have a low vertical resolution in the upper troposphere and lower stratosphere (UTLS) region, substantial uncertainties remain in atmospheric dynamics in the UTLS during El Niño and La Niña conditions.

In this context radio occultation (RO) offers new possibilities by providing high quality observations in the UTLS with global coverage. Atmospheric parameters like temperature, pressure, and geopotential height are retrieved with high vertical resolution and high accuracy and precision. A continuous RO record is available since 2001 but the number of RO measurements increased significantly in 2006, with the launch of the six Formosat-3/COSMIC (F3C) satellites. This constellation tracked more than 2000 RO events per day, enabling the derivation of fine-resolved atmospheric fields.

The central aim of the proposed project DYNOCC is the assessment of ENSO related atmospheric dynamics and its effects on troposphere-stratosphere processes from this novel multi-year RO record. In a first step I will perform a thorough investigation of UTLS ENSO signals in temperature, pressure, geopotential height, and water vapor to analyze the detailed vertical and horizontal structure of ENSO. The consistency of results obtained from RO will be checked using data from other observations as well as from analyses and reanalyses. Furthermore, I will validate a state-of-the-art global climate model with regard to its representation of the vertical UTLS ENSO structure. In a second step I will use high resolution RO data to investigate details of atmospheric waves associated with local heating induced by El Niño. This will allow gaining deeper understanding of natural climate variability in the transition between the troposphere and stratosphere, an important coupling layer in the atmosphere which is a topic of active current research. Finally, I will use precise RO-based geopotential height profiles on constant pressure surfaces to investigate the vertical and horizontal displacement of the geostrophic zonal wind during El Niño and La Niña conditions.

Addressing these key issues, DYNOCC aims at adding detailed understanding of atmospheric dynamics associated with natural climate variability. Extending the application of RO to further research fields, DYNOCC will strengthen its value also outside of the RO community.


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