Evaluating the Model Representation of Asian Summer Monsoon Upper Troposphere and Lower Stratosphere Transport and Composition Using Airborne In Situ Observations

Year: 2024

Authors: Smith WP., Pan LL., Kinnison D., Atlas E., Honomichl S., Zhang J., Tilmes S., Fernandez RP., Saiz-Lopez A., Treadaway V., Adcock KE., Laube JC., von Hobe M., Kloss C., Viciani S., D’Amato F., Volk CM., Ravegnani F.

Autors Affiliation: NSF Natl Ctr Atmospher Res, Atmospher Chem Observat & Modeling Lab, Boulder, CO 80305 USA; Univ Miami, Rosenstiel Sch Marine Atmospher & Earth Sci, Dept Atmospher Sci, Miami, FL USA; Natl Res Council CONICET, Inst Interdisciplinary Sci ICB, Mendoza, Argentina; CSIC, Inst Phys Chem Blas Cabrera, Dept Atmospher Chem & Climate, Madrid, Spain; Univ Colorado Boulder, Cooperat Inst Res Environm Sci, Boulder, CO USA; NOAA, Chem Sci Lab, Boulder, CO USA; Univ East Anglia, Ctr Ocean & Atmospher Sci, Sch Environm Sci, Norwich, England; Forschungszentrum Julich, Inst Energy & Climate Res IEK 7, Julich, Germany; CNR, Natl Inst Opt CNR INO, Sesto Fiorentino, Italy; Univ Wuppertal, Wuppertal, Germany; CNR, Inst Atmospher Sci & Climate CNR ISAC, Bologna, Italy.

Abstract: Chemistry Climate Models (CCMs) are essential tools for characterizing and predicting the role of atmospheric composition and chemistry in Earth’s climate system. This study demonstrates the use of airborne in situ observations to diagnose the representation of chemical composition and transport by CCMs. Process-based diagnostics using dynamical and chemical coordinates are presented which minimize the spatial and temporal sampling differences between airborne in situ measurements and CCM grid points. The chosen process is the chemical impact of the Asian summer monsoon (ASM), where deep convection serves as a rapid transport pathway for surface emissions to reach the upper troposphere and lower stratosphere (UTLS). We examine two CCM configurations for their representation of the ASM UTLS using a set of airborne observations from south Asia. The diagnostics reveal good model performance at representing tropospheric tracer distribution throughout the troposphere and lower stratosphere, and excellent representation of chemical aging in the lower stratosphere when chemical loss is dominated by photolysis. Identified model limitations include the use of zonally averaged mole fraction boundary conditions for species with sufficiently short tropospheric lifetimes, which may obscure enhanced regional emissions sources. Overall, the diagnostics underscore the skill of current-generation models at representing pollution transport from the boundary layer to the stratosphere via the ASM mechanism, and demonstrate the strength of airborne in situ observations toward characterizing this representation. The chemical composition of Earth’s atmosphere is important to understand for future climate prediction. This study establishes an approach for evaluating the representation of chemical composition in global climate models, and demonstrates the capabilities of the approach using a set of observations collected by research aircraft. We specifically target an evaluation of the Asian summer monsoon, a process with a well-documented transport pathway for chemical species near the surface to reach the upper atmosphere. In doing so, we identify specific areas where focused model improvement is needed. Process-based diagnostics for model evaluation using airborne in situ observations are presented The Asian summer monsoon is explored for its role in impacting global composition and climate The diagnostics use dynamical and chemical coordinates to identify model strengths and limitations

Journal/Review: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES

Volume: 129 (4)      Pages from: e2023JD039756-1  to: e2023JD039756-1

More Information: The National Center for Atmospheric Research (NCAR) is supported by the National Science Foundation (NSF). W.P.S. was supported under grant NSF AGS-1853929. K.E.A. was funded by the UK Natural Environment Research Council through the EnvEast Doctoral Training Partnership (Grant Number NE/L002582/1). We acknowledge high-performance computing support from Cheyenne () provided by NCAR’s Computational and Information Systems Laboratory (CISL), sponsored by the NSF. Airborne measurements were made possible by European Community’s Seventh Framework Programme (FP7/2007-2013), grant agreement 603557-Project STRATOCLIM. We acknowledge support from the Geophysica aircraft team, the StratoClim science team and the NCAR multi-scale modeling community, as well as helpful comments from M. Barth, W. Randel and E. Weatherhead.
KeyWords: Asian summer monsoon; convective transport; model diagnostics; composition; chemical loss
DOI: 10.1029/2023JD039756

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