Intercalibrating microwave satellite observations for monitoring long-term variations in upper- and midtropospheric water vapor

Eui Seok Chung, Brian J. Soden, Viju O. John

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


This paper analyzes the growing archive of 183-GHz water vapor absorption band measurements from the Advanced Microwave Sounding Unit B (AMSU-B) and Microwave Humidity Sounder (MHS) on board polar-orbiting satellites and document adjustmentsnecessary to use the data for long-term climate monitoring. The water vapor channels located at 183.31 6 1GHz and 183.31 6 3GHz are sensitive to upper- and midtropospheric relative humidity and less prone to the clear-sky sampling bias than infrared measurements, making them a valuable but underutilized source of information on free-tropospheric water vapor. A method for the limb correction of the satellite viewing angle based upon a simplified model of radiative transfer is introduced toremove the scan angle dependence of the radiances. Biases due to the difference inlocal observation time between satellites and spurious trends associated with satellite orbital drift are then diagnosed and adjusted for using synthetic radiative simulations based on the Interim European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-Interim). The adjusted, cloud-filtered, and limbcorrected brightness temperatures are then intercalibrated using zonal-mean brightness temperature differences. It is found that these correction procedures significantly improve consistency and quantitative agreement between microwave radiometric satellite observations that can be used to monitor upper- and midtropospheric water vapor. The resulting radiances are converted to estimates of the deep-layer-mean upper- and midtropospheric relative humidity, and can be used to evaluate trends in upper-tropospheric relative humidity from reanalysis datasets and coupled ocean-atmosphere models.

Original languageEnglish (US)
Pages (from-to)2303-2319
Number of pages17
JournalJournal of Atmospheric and Oceanic Technology
Issue number10
StatePublished - Oct 2013


  • Climate records
  • Microwave observations
  • Radiative transfer
  • Trends
  • Water vapor

ASJC Scopus subject areas

  • Ocean Engineering
  • Atmospheric Science


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