Microwave Limb Sounder

Contact: Nathaniel Livesey 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 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 (Core+R4A) retrievals. 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 Product Information Line Listing Quick Product Information for Data Version v3.3 Swath Name: BrO Vertical Resolution: 5.5km at 10 - 4.6 hPa 6km at 3.2 hPa Useful Range: 10 - 3.2hPa DAAC Short Name: ML2BRO Precision: +/- 4 pptv (monthly 10 degree zonal mean) at 10 - 4.6 hPa Quality Threshold: 1.3

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v3.3 BrO Averaging Kernel

colored lines are individual kernels; thick dashed line is full width at half maximum, thick solid is integrated kernel value

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Publications related to the MLS BrO data product

2007

1. Kovalenko, L.J., "Validation of the Aura Microwave Limb Sounder BrO observations in the stratosphere", vol doi:10.1029/2007JD008817, num 112, 2007. Reprint Preprint

2006

1. Cofield, R.E., "Design and field-of-view calibration of 114-660 GHz optics of the Earth Observing System Microwave Limb Sounder", num 44, pgs. no. 5, 2006. Preprint
2. Livesey, N.J., "EOS Microwave Limb Sounder observations of upper stratospheric BrO: Implications for total bromine", vol doi:10.1029/2006GL026930, num 33, 2006. Preprint

2003

1. Yamada, M.M., "Submillimeter-wave Measurements of the Pressure Broadening of BrO", num 82, pgs. Issue 1-4, 2003. Reprint Preprint

2001

1. Drouin, B.J., "The rotational spectra, isotopically independent parameters, and interatomic potentials for the X₁ ²Pi_3/2 and X₂ ²Pi_1/2 states of BrO", num 205, 2001. Preprint