Validation of the Improved Limb Atmospheric Spectrometer-II (ILAS-II) Version 1.4 nitrous oxide and methane profiles

M. K. Ejiri, Y. Terao, T. Sugita, H. Nakajima, T. Yokota, G. C. Toon, B. Sen, G. Wetzel, H. Oelhaf, J. Urban, D. Murtagh, H. Irie, N. Saitoh, T. Tanaka, H. Kanzawa, M. Shiotani, S. Aoki, G. Hashida, T. Machida, T. NakazawaH. Kobayashi, Y. Sasano

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


This study assesses polar stratospheric nitrous oxide (N2O) and methane (CH4) data from the Improved Limb Atmospheric Spectrometer-II (ILAS-II) on board the Advanced Earth Observing Satellite-II (ADEOS-II) retrieved by the Version 1.4 retrieval algorithm. The data were measured between January and October 2003. Vertical profiles of ILAS-II volume mixing ratio (VMR) data are compared with data from two balloon-borne instruments, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) and the MkIV instrument, as well as with two satellite sensors, the Odin Sub-Millimetre Radiometer (SMR) for N2O and the Halogen Occultation Experiment (HALOE) for CH4. Relative percentage differences between the ILAS-II and balloon/satellite data and their median values are calculated in 10-ppbv-wide bins for N2O (from 0 to 400 ppbv) and in 0.05-ppmv-wide bins for CH4 (from 0 to 2 ppmv) in order to assess systematic differences between the ILAS-II and balloon/satellite data. According to this study, the characteristics of the ILAS-II Version 1.4 N2O and CH4 data differ between hemispheres. For ILAS-II N2O VMR larger than 250 ppbv, the ILAS-II N2O agrees with the balloon/SMR N2O within ±20% in both hemispheres. The ILAS-II N2O in the VMR range from 30-50 to 250 ppbv (corresponding to altitudes of ∼17-30 km in the Northern Hemisphere (NH, mainly outside the polar vortex) and ∼13-21 km in the Southern Hemisphere (SH, mainly inside the polar vortex) is smaller by ∼10-30% than the balloon/SMR N2O. For ILAS-II N2O VMR smaller than 30 ppbv (>∼21 km) in the SH, the differences between the ILAS-H and SMR N2O are within ±10 ppbv. For ILAS-II CH4 VMR larger than 1 ppmv (<∼25 km), the ILAS-II CH4 agrees with the balloon/HALOE CH4 within ±5% in the NH. For ILAS-II CH4 VMR larger than 0.3 ppmv in SH, the ILAS-II CH4 is ∼9% larger than the HALOE CH4; note that this positive systematic difference between the ILAS-II and HALOE CH4 has a seasonal dependence. Also note that the ILAS-II N2O for its VMR smaller than 50 ppbv (>∼30 km) and the ILAS-II CH4 for its VMR smaller than 1 ppmv (>∼25 km) only in the NH, are abnormally small compared to the balloon/satellite data.

Original languageEnglish
Article numberD22S90
JournalJournal of Geophysical Research Atmospheres
Issue number22
Publication statusPublished - 2006 Nov 27
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Oceanography
  • Forestry
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Palaeontology


Dive into the research topics of 'Validation of the Improved Limb Atmospheric Spectrometer-II (ILAS-II) Version 1.4 nitrous oxide and methane profiles'. Together they form a unique fingerprint.

Cite this