A statistical comparison of zonal mean and tidal signatures in FORMOSAT-3/COSMIC and ground-based GPS TECs

Loren C. Chang, Charles C.H. Lin, Jann Yenq Liu

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2 Scopus citations


Atmospheric tidal components in the ionosphere can reflect either the in-situ generated quiet-time variation in the ionosphere, or vertically propagating tidal components generated through coupling to lower or middle atmosphere phenomena. Frequency-wavenumber tidal decomposition is a valuable tool for isolating the primary tidal components that drive the dynamics of the middle and upper atmosphere, allowing temporal and spatial variability to be quantified in a systematic manner, provided sufficient local time sampling. To date, two commonly used data sources for such tidal studies in the ionosphere are the FORMOSAT-3/COSMIC (F3/C) satellite constellation and ground-based GPS-derived Global Ionosphere Maps (GIMs). In this study, the migrating diurnal and semidiurnal tidal components, the nonmigrating diurnal eastward 3 (DE3) component, as well as the zonal mean component that dominate quiet-time ionospheric variability are extracted from 2008 F3/C and GIM Total Electron Content (TEC) data, using integration times of 20 days. We find that the zonal mean and tidal TEC components in F3/C and ground-based GIM data show qualitatively similar seasonal variability and spatial structure. However, the maximum amplitudes of the zonal mean and migrating tidal components computed from F3/C are consistently smaller than those from the ground-based GIMs, revealing a systematic difference between the two datasets. Conversely, the DE3 amplitudes are generally larger in F3/C compared to GIM, potentially due to the higher zonal wavenumber of that component.

Original languageEnglish
Pages (from-to)253-263
Number of pages11
JournalTerrestrial, Atmospheric and Oceanic Sciences
Issue number2
StatePublished - Apr 2013


  • Atmospheric tides
  • GIM
  • Ionosphere
  • TEC
  • Validation


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