Contact: Lucien Froidevaux
Although HOCl is not a major chlorine gas in terms of the atmospheric chlorine budget or ozone destruction, it does play some role in the chemical ozone destruction cycles and there are still significant uncertainties in its rate of formation (from ClO and HO2).
How it is part of MLS Science Objectives
Although HOCl is not a major chlorine gas in terms of the atmospheric chlorine budget or ozone destruction, it does play some role in the chemical ozone destruction cycles and there are still significant uncertainties in its rate of formation (from ClO and HO2). Obtaining global measurements of this product could help constrain some of these uncertainties.
How EOS MLS measures HOCl
The standard product for HOCl is taken from the 640 GHz retrievals. Simulations indicate that enhanced lower stratospheric values of 0.5 to 1 ppbv may be tracked at the 20% level, in single profiles. Real data systematics for HOCl, however, lead us to recommend a maximum pressure of 10 hPa.
HOCl is a noisy product and its typical stratospheric abundance is expected to be less than ~200 pptv, except under heterogeneously-enhanced conditions in the lower stratospheric winter polar vortex, where larger abundances of order 0.5 - 1 ppbv may occasionally be found.
We feel that zonal mean information (e.g., in 10°-wide bins) from one day's worth of MLS data is marginally useful, although monthly or bi-weekly averages will reduce the noise to more practical levels.
MLS values show a reasonable behavior in the upper stratosphere but have a tendency to be somewhat lower than other data (balloon data), and lower also (from a rough comparison) than the MIPAS published values (Von Clarmann et al., JGR, 2006) for Sep./Oct. 2002. More progress in the MLS retrievals for HOCl may come from (off-line) retrievals using averaged radiances or other methods in the future.
HOCl Information from the Spectroscopy Database
Quick Product Information for data version v5
- Swath Name: HOCl
- Status Flag: Only use profiles for which the Status field is an even number.
- Useful Range: 10 - 2.2 hPa
- DAAC Short Name: ML2HOCL
- Precision: Only use values for which the estimated precision is a positive number.
- Quality Threshold: >1.2
- Convergence Threshold: <1.05
Latest Publications (HOCl)
Froidevaux, L., D. Kinnison, M. Santee, L. Millán, N. Livesey, W. Read, C. Bardeen, J. Orlando and R. Fuller
Upper stratospheric ClO and HOCl trends (2005-2020): Aura Microwave Limb Sounder and model resultsAtmos. Chem. Phys. 10.5194/acp-22-4779-2022, 2022
Hegglin, M., S. Tegtmeier, J. Anderson, A. Bourassa, S. Brohede, D. Degenstein, L. Froidevaux, B. Funke, J. Gille, Y. Kasai, E. Kyrölä, J. Lumpe, D. Murtagh, J. Neu, K. Pérot, E. Remsberg, A. Rozanov, M. Toohey, J. Urban, T. von Clarmann, K. Walker, H. Wang, C. Arosio, R. Damadeo, R. Fuller, G. Lingenfelser, C. McLinden, D. Pendlebury, C. Roth, N. Ryan, C. Sioris, L. Smith and K. Weigel
Overview and update of the SPARC Data Initiative: comparison of stratospheric composition measurements from satellite limb soundersEarth System Science Data doi:10.5194/essd-13-1855-2021, 2021
Häkkilä, T., P. Verronen, L. Millán, M. Szeląg, N. Kalakoski and A. Kero
Odd hydrogen response thresholds for indication of solar proton and electron impact in the mesosphere and stratosphereAnnales Geophysicae 10.5194/angeo-38-1299-2020, 2020
Hegglin, M., S. Tegtmeier, J. Anderson, A. Bourassa, S. Brohede, D. Degenstein, L. Froidevaux, B. Funke, J. Gille, A. Jones, Y. Kasai, E. Kyrola, J. Lumpe, J. Neu, E. Remsberg, A. Rozanov, M. Toohey, J. Urban, T. von Clarmann, K.A. Walker and R. Wang
The SPARC Data Initiative: Assessment of stratospheric trace gas and aerosol climatologies from satellite limb soundersSPARC Report https://dx.doi.org/10.3929/ethz-a-010863911, 2017
Khosravi, M., P. Baron, J. Urban, L. Froidevaux, A.I. Jonsson, Y. Kasai, K. Kuribayashi, C. Mitsuda, D.P. Murtagh, H. Sagawa, M.L. Santee, T.O. Sato, M. Shiotani, M. Suzuki, T. von Clarmann, K.A. Walker and S. Wang
Diurnal variation of stratospheric and lower mesospheric HOCl, ClO and HO2 at the equator: comparison of 1-D model calculations with measurements by satellite instrumentsAtmos. Chem. Phys. doi:10.5194/acp-13-7587-2013, 2013
Damiani, A., B. Funke, D.R. Marsh, M. Lopez-Puertas, M.L. Santee, L. Froidevaux, S. Wang, C.H. Jackman, T. von Clarmann, A. Gardini, R.R. Cordero and M. Storini
Impact of January 2005 solar proton events on chlorine speciesAtmos. Chem. Phys. doi:10.5194/acp-12-4159-2012, 2012
Cofield, R.E. and P.C. Stek
Design and field-of-view calibration of 114-660 GHz optics of the Earth Observing System Microwave Limb SounderIEEE Trans. Geosci. Remote Sensing doi:10.1109/TGRS.2006.873234, 2006