TY - JOUR
T1 - Inter-model comparison of global hydroxyl radical (OH) distributions and their impact on atmospheric methane over the 2000-2016 period
AU - Zhao, Yuanhong
AU - Saunois, Marielle
AU - Bousquet, Philippe
AU - Lin, Xin
AU - Berchet, Antoine
AU - Hegglin, Michaela I.
AU - Canadell, Josep G.
AU - Jackson, Robert B.
AU - Hauglustaine, Didier A.
AU - Szopa, Sophie
AU - Stavert, Ann R.
AU - Luke Abraham, Nathan
AU - Archibald, Alex T.
AU - Bekki, Slimane
AU - Deushi, Makoto
AU - Jöckel, Patrick
AU - Josse, Béatrice
AU - Kinnison, Douglas
AU - Kirner, Ole
AU - Marécal, Virginie
AU - O'Connor, Fiona M.
AU - Plummer, David A.
AU - Revell, Laura E.
AU - Rozanov, Eugene
AU - Stenke, Andrea
AU - Strode, Sarah
AU - Tilmes, Simone
AU - Dlugokencky, Edward J.
AU - Zheng, Bo
N1 - Publisher Copyright:
© 2019 BMJ Publishing Group. All rights reserved.
PY - 2019
Y1 - 2019
N2 - The modeling study presented here aims to estimate how uncertainties in global hydroxyl radical (OH) distributions, variability, and trends may contribute to resolving discrepancies between simulated and observed methane (CH4) changes since 2000. A multi-model ensemble of 14 OH fields was analyzed and aggregated into 64 scenarios to force the offline atmospheric chemistry transport model LMDz (Laboratoire de Meteorologie Dynamique) with a standard CH4 emission scenario over the period 2000-2016. The multi-model simulated global volume-weighted tropospheric mean OH concentration ([OH]) averaged over 2000-2010 ranges between 8:7 × 105 and 12:8 × 105 molec cm-3. The inter-model differences in tropospheric OH burden and vertical distributions are mainly determined by the differences in the nitrogen oxide (NO) distributions, while the spatial discrepancies between OH fields are mostly due to differences in natural emissions and volatile organic compound (VOC) chemistry. From 2000 to 2010, most simulated OH fields show an increase of 0.1-0:3 × 105 molec cm-3 in the tropospheric mean [OH], with year-to-year variations much smaller than during the historical period 1960-2000. Once ingested into the LMDz model, these OH changes translated into a 5 to 15 ppbv reduction in the CH4 mixing ratio in 2010, which represents 7 %-20 % of the model-simulated CH4 increase due to surface emissions. Between 2010 and 2016, the ensemble of simulations showed that OH changes could lead to a CH4 mixing ratio uncertainty of > ±30 ppbv. Over the full 2000-2016 time period, using a common stateof-the-art but nonoptimized emission scenario, the impact of [OH] changes tested here can explain up to 54 % of the gap between model simulations and observations. This result emphasizes the importance of better representing OH abundance and variations in CH4 forward simulations and emission optimizations performed by atmospheric inversions.
AB - The modeling study presented here aims to estimate how uncertainties in global hydroxyl radical (OH) distributions, variability, and trends may contribute to resolving discrepancies between simulated and observed methane (CH4) changes since 2000. A multi-model ensemble of 14 OH fields was analyzed and aggregated into 64 scenarios to force the offline atmospheric chemistry transport model LMDz (Laboratoire de Meteorologie Dynamique) with a standard CH4 emission scenario over the period 2000-2016. The multi-model simulated global volume-weighted tropospheric mean OH concentration ([OH]) averaged over 2000-2010 ranges between 8:7 × 105 and 12:8 × 105 molec cm-3. The inter-model differences in tropospheric OH burden and vertical distributions are mainly determined by the differences in the nitrogen oxide (NO) distributions, while the spatial discrepancies between OH fields are mostly due to differences in natural emissions and volatile organic compound (VOC) chemistry. From 2000 to 2010, most simulated OH fields show an increase of 0.1-0:3 × 105 molec cm-3 in the tropospheric mean [OH], with year-to-year variations much smaller than during the historical period 1960-2000. Once ingested into the LMDz model, these OH changes translated into a 5 to 15 ppbv reduction in the CH4 mixing ratio in 2010, which represents 7 %-20 % of the model-simulated CH4 increase due to surface emissions. Between 2010 and 2016, the ensemble of simulations showed that OH changes could lead to a CH4 mixing ratio uncertainty of > ±30 ppbv. Over the full 2000-2016 time period, using a common stateof-the-art but nonoptimized emission scenario, the impact of [OH] changes tested here can explain up to 54 % of the gap between model simulations and observations. This result emphasizes the importance of better representing OH abundance and variations in CH4 forward simulations and emission optimizations performed by atmospheric inversions.
UR - https://www.scopus.com/pages/publications/85075078291
U2 - 10.5194/acp-19-13701-2019
DO - 10.5194/acp-19-13701-2019
M3 - Article
AN - SCOPUS:85075078291
SN - 1680-7316
VL - 19
SP - 13701
EP - 13723
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 21
ER -