Methyl chloride (chloromethane, CH3Cl) is the most abundant chlorine-containing compound in the atmosphere. As the largest natural source of stratospheric chlorine, CH3Cl contributed 16% of the stratospheric total inorganic chlorine budget in 2000 and thus accounts for a significant fraction of chlorine-catalyzed ozone destruction. Known sources of CH3Cl emissions are predominantly natural, although biomass burning (most of which is human-induced) was recently estimated to account for nearly 25% of its global source strength.
The CH3CL Molecule
How it is part of MLS Science Objectives
The importance of CH3Cl is expected to increase in the future as emission controls alter the relative contributions from natural and anthropogenic halogen sources. Moreover, since CH3Cl emissions from many natural sources vary depending on environmental conditions, changes in global climate and land use patterns may increase CH3Cl fluxes, potentially offsetting some of the projected decline in stratospheric chlorine and delaying ozone recovery.
Thus the MLS CH3Cl measurements will establish a baseline against which the future stratospheric CH3Cl burden may be assessed.
How EOS MLS measures CH3Cl
The standard methyl chloride product is taken from the 640 GHz retrieval.
Quick Product Information for data version v4.2
- Swath Name: CH3Cl
- Status Flag: Only use profiles for which the Status field is zero.
- Useful Range: 147 - 4.6 hPa
- DAAC Short Name: ML2CH3CL
- Precision: Only use values for which the estimated precision is a positive number.
- Quality Threshold: >1.3
- Convergence Threshold: <1.05
|Download EOS Aura MLS CH3Cl v4.2 data
Publications related to the MLS CH3Cl data product
- Johansson, S., M. Santee, J. Grooß, M. Höpfner, M. Braun, F. Friedl-Vallon, F. Khosrawi, O. Kirner, E. Kretschmer, H. Oelhaf, J. Orphal, B. Sinnhuber, I. Tritscher, J. Ungermann, K. Walker, W. Woiwode, "Unusual chlorine partitioning in the 2015/16 Arctic winter lowermost stratosphere: observations and simulations", Atmospheric Chemistry and Physics 19, 12, 8311-8338, doi:10.5194/acp-19-8311-2019, 2019. reprint
- Santee, M.L., G.L. Manney, N.J. Livesey, M.J. Schwartz, J.L. Neu, W.G. Read, "A comprehensive overview of the climatological composition of the Asian summer monsoon anticyclone based on 10 years of Aura Microwave Limb Sounder measurements", Journal of Geophysical Research: Atmospheres 122, doi:10.1002/2016jd026408, 2017. reprint
- Millan, L., N. Livesey, M. Santee, J. Neu, G. Manney, R. Fuller, "Case studies of the impact of orbital sampling on stratospheric trend detection and derivation of tropical vertical velocities: solar occultation vs. limb emission sounding", Atmospheric Chemistry and Physics 16, 18, 11521-11534, doi:10.5194/acp-16-11521-2016, 2016. reprint
- Manney, G., Z. Lawrence, M. Santee, W. Read, N. Livesey, A. Lambert, L. Froidevaux, H. Pumphrey, M. Schwartz, "A minor sudden stratospheric warming with a major impact: Transport and polar processing in the 2014/2015 Arctic winter", Geophysical Research Letters 42, 18, 7808-7816, doi:10.1002/2015gl065864, 2015. reprint
- Santee, M.L., N.J. Livesey, G.L. Manney, A. Lambert, W.G. Read, "Methyl chloride from the Aura Microwave Limb Sounder: First global climatology and assessment of variability in the upper troposphere and stratosphere", Journal of Geophysical Research: Atmospheres 118, 24, 13532-13560, doi:10.1002/2013JD020235, 2013. reprint
- Pumphrey, H.C., M.L. Santee, N.J. Livesey, M.J. Schwartz, W.G. Read, "Microwave Limb Sounder observations of biomass-burning products from the Australian bush fires of February 2009", Atmospheric Chemistry and Physics 11, 2, 6285-6296, doi:10.5194/acp-11-6285-2011, 2011. reprint