Simulating CH4 and CO2 over South and East Asia using the zoomed chemistry transport model LMDzINCA
Xin Lin1, Philippe Ciais1, Philippe Bousquet1, Michel Ramonet1, Yi Yin1, Yves Balkanski1, Anne Cozic1, Marc Delmotte1, Nikolaos Evangeliou2, Nuggehalli K. Indira3, Robin Locatelli1,a, Shushi Peng4, Shilong Piao4, Marielle Saunois1, Panangady S. Swathi3, Rong Wang1, Camille Yver-Kwok1, Yogesh K. Tiwari5, and Linxi Zhou61Laboratoire des Sciences du Climat et de l’Environnement, LSCE - IPSL (CEA - CNRS -UVSQ), Université Paris - Saclay, 91191 Gif - sur - Yvette, France 2Norwegian Institute for Air Researh (NILU), Department of Atmospheric and Climate Research (ATMOS), Kjeller, Norway 3CSIR Fourth Paradigm Institute (formerly CSIR Centre for Mathematical Modelling and Computer Simulation), NAL Belur Campus, Bengaluru 560 037, India 4Sino-French Institute for Earth System Science, College of Urban and Environment Sciences, Peking University, Beijing 100871, China 5Centre for Climate Change Research, I ndian Institute of Tropical Meteorology, Pune, India 6Chinese Academy of Meteorological Sciences (CAMS), China Meteorological Administration (CMA), Beijing, China aNow at: AXA Global P&C, Paris, France
Received: 27 Nov 2016 – Accepted for review: 06 Mar 2017 – Discussion started: 07 Mar 2017
Abstract. The increasing availability of atmospheric measurements of greenhouse gases (GHGs) from surface stations can improve the retrieval of their fluxes at higher spatial and temporal resolutions by inversions, provided that chemistry transport models are able to properly represent the variability of concentrations observed at different stations. South and East Asia (SEA) is a region with large and very uncertain emissions of carbon dioxide (CO2) and methane (CH4), the most potent anthropogenic GHGs. Monitoring networks have expanded greatly during the past decade in this region, which should contribute to reducing uncertainties in estimates of regional GHG budgets. In this study, we simulate concentrations of CH4 and CO2 using a zoomed version of the global chemistry transport model LMDzINCA during the period 2006–2013. The zoomed version has a fine horizontal resolution of ~ 0.66° in longitude and ~0.51° in latitude over SEA and a coarser resolution elsewhere. The concentrations of CH4 and CO2 simulated from the zoomed model (abbreviated as ‘ZASIA’) are compared to those from the same model but with a uniform regular grid of 2.50° in longitude and 1.27° in latitude (abbreviated as ‘REG’), both having the same vertical 19 sigma pressure levels and prescribed with the same biogenic and anthropogenic fluxes. Model performance is evaluated for annual gradients between sites, seasonal, synoptic and diurnal variations, against a new dataset including 30 surface stations over SEA and adjacent regions. Our results show that, when prescribed with identical surface fluxes, compared to REG, the ZASIA version moderately improves the representation of CH4 mean annual gradients between stations as well as the seasonal and synoptic variations of this trace gas within the zoomed region. This moderate improvement probably results from reduction of representation errors and a better description of the CH4 concentration gradients related to the skewed spatial distribution of surface CH4 emissions, suggesting that the zoom transport model will be better suited for inversions of CH4 fluxes in SEA. With the relatively coarse vertical resolution and low-frequency (monthly) prescribed fluxes, the model generally does not capture the diurnal cycle of CH4 at most stations even with its zoomed configuration, emphasizing the need to increase the vertical resolution, and to improve parameterizations of turbulent diffusion in the planetary boundary layer and deep convection during the monsoon period. The model performance for CH4 is better than that for CO2 at any temporal scale, likely due to inaccuracies in the CO2 fluxes prescribed in this study.
Lin, X., Ciais, P., Bousquet, P., Ramonet, M., Yin, Y., Balkanski, Y., Cozic, A., Delmotte, M., Evangeliou, N., Indira, N. K., Locatelli, R., Peng, S., Piao, S., Saunois, M., Swathi, P. S., Wang, R., Yver-Kwok, C., Tiwari, Y. K., and Zhou, L.: Simulating CH4 and CO2 over South and East Asia using the zoomed chemistry transport model LMDzINCA, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1056, in review, 2017.