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Contact: Luis Millan Valle

Basic Information

Bromine monoxide (BrO) is important in the catalytic destruction of stratospheric ozone, especially in the lower stratosphere (below about 20 km). Model studies indicate that catalytic cycles involving BrO may account for as much as 60% of ozone loss for very cold Arctic winters. Bromine monoxide is the main daytime constituent of stratospheric inorganic bromine (Bry), making up about 50% of Bry. The other Bry constituents are Br, HOBr, BrONO2, HBr, and BrCl. In contrast, for stratospheric inorganic chlorine (Cly), the reactive constituents (Cl and ClO) make up only a few percent of Cly.

To quantify the impact of inorganic bromine on stratospheric ozone loss, accurate measurements of its abundance are needed. However, because of their low abundances (several ppt), relatively few measurements have been made of its constituents. Therefore Bry is typically estimated from stratospheric measurements of BrO, combined with estimates of the other constituents from photochemical models. One current problem is that estimates of Bry from measurements of stratospheric BrO obtained by various satellite and balloon-borne instruments show some disagreement.

A second current problem is that estimates of Bry from measurements of stratospheric BrO tend to exceed predictions of Bry based on measurements of the organic source gases from which Bry is believed to be derived (CH3Br and halons). It is currently strongly suspected that there may be additional sources of stratospheric inorganic bromine.
The BrO Molecule
BrO molecule visualization

How it is part of MLS Science Objectives

One of the objectives for MLS and the Aura mission is to understand and monitor changes in the chemistry and atmospheric composition that can affect stratospheric ozone. Measurements of stratospheric BrO, the dominant form of bromine in the stratosphere and the dominant form of bromine directly involved in ozone destruction, will help quantify the contribution of Bry to ozone loss.

How EOS MLS measures BrO

The standard product for BrO is taken from the 640-GHz retrieval. The spectral signature of BrO in the MLS radiances is very small, leading to a poor signal to noise ratio on individual MLS observations. Some form of averaging (e.g. monthly zonal means) is required to obtain scientifically useful results.

BrO Information from the Spectroscopy Database

Quick Product Information for Data Version v4.2

  • Swath Name: BrO
  • Status Flag: Only use profiles for which the Status field is an even number.
  • Useful Range: 10 – 3.2 hPa (day/night di erences needed)
  • DAAC Short Name: ML2BRO
  • Precision: Only use values for which the estimated precision is a positive number.
  • Quality Threshold: >1.3
  • ConvergenceThreshold: <1.05
Download EOS Aura MLS BrO v4.2 data

Publications related to the MLS BrO data product


  1. Stachnik, R.A., L. Millan, R. Jarnot, R. Monroe, C. McLinden, S. Kühl, J. Puķīte, M. Shiotani, M. Suzuki, Y. Kasai, F. Goutail, J.P. Pommereau, M. Dorf, K. Pfeilsticker, "Stratospheric BrO abundance measured by a balloon-borne submillimeterwave radiometer", Atmospheric Chemistry and Physics 13, 3307-3319, doi:10.5194/acp-13-3307-2013, 2013. reprint


  1. Millan, L., N.J. Livesey, L. Froidevaux, D. Kinnison, R. Harwood, I.A. MacKenzie, M.P. Chipperfield, "New Aura Microwave Limb Sounder observations of BrO and implications for Bry", Atmospheric Measurement Techniques, doi:10.5194/amt-5-1741-2012, 2012. reprint


  1. Kovalenko, L.J., N.J. Livesey, R.J. Salawitch, C. Camy-Peyret, M.P. Chipperfield, R.E. Cofield, M. Dorf, B.J. Drouin, L. Froidevaux, R.A. Fuller, F. Goutail, R.F. Jarnot, K. Jucks, B.W. Knosp, A. Lambert, I.A. MacKenzie, K. Pfeilsticker, J-P. Pommereau, W.G. Read, M.L. Santee, M.J. Schwartz, W.V. Snyder, R. Stachnik, P.C. Stek, P.A. Wagner, J.W. Waters, "Validation of the Aura Microwave Limb Sounder BrO observations in the stratosphere", Journal of Geophysical Research 112, D24S41, doi:10.1029/2007JD008817, 2007. reprint


  1. Cofield, R.E., P.C. Stek, "Design and field-of-view calibration of 114-660 GHz optics of the Earth Observing System Microwave Limb Sounder", IEEE Transactions on Geoscience and Remote Sensing 44, no. 5, 1166-1181, doi:10.1109/TGRS.2006.873234, 2006. reprint
  2. Livesey, N.J., L.J. Kovalenko, R.J. Salawitch, I.A. MacKenzie, M.P. Chipperfield, W.G. Read, R.F. Jarnot, J.W. Waters, "EOS Microwave Limb Sounder observations of upper stratospheric BrO: Implications for total bromine", Geophysical Research Letters 33, L20817, doi:10.1029/2006GL026930, 2006. reprint


  1. Yamada, M.M., M. Kobayashi, H. Habara, T. Amano, B.J. Drouin, "Submillimeter-wave Measurements of the Pressure Broadening of BrO", Journal of Quantitative Spectroscopy and Radiative Transfer 82, Issue 1-4, 391-399, doi:10.1016/S0022-4073(03)00165-1, 2003. reprint


  1. Drouin, B.J., C.E. Miller, H S.P. Muller, E.A. Cohen, "The rotational spectra, isotopically independent parameters, and interatomic potentials for the X1 2Pi3/2 and X2 2Pi1/2 states of BrO", Journal of Molecular Spectroscopy 205, 128-138, doi:10.1006/jmsp.2000.8252, 2001. reprint

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