@article{15b141349ace4c63921453d3fe42bc5c,
title = "Observations of Greenhouse Gas Changes Across Summer Frontal Boundaries in the Eastern United States",
abstract = "Our knowledge about synoptic-scale variations of atmospheric-CO2 produced by interactions between midlatitude cyclones and regional-scale surface fluxes remains limited due to the scarcity of observations. We synthesized observations of greenhouse gases (GHGs) with respect to frontal passages to understand how GHG distributions change vertically and horizontally during a synoptic event. We use the airborne in situ measurements of GHGs collected during the Atmospheric Carbon and Transport-America summer 2016 field campaign. Using these measurements, we defined three metrics, (1) the differences in the GHG mole fractions across frontal boundaries in the atmospheric boundary layer (BL) and free troposphere (FT), (2) differences in the vertical contrasts in GHGs in warm and cold sectors, and (3) the size and magnitude of enhanced CO2 in the vicinity of frontal boundary. We found that frontal structures are clearly associated with spatially coherent and significant changes in GHG composition. Warm sector CO2 mole fractions [CO2] are higher than those in the cold sector. The cross-frontal [CO2] contrasts are largest in the BL (5–30 ppm) with smaller differences in the FT (3–5 ppm). We found higher [CH4] in the BL in the warm sector than in the cold sector for 5 out of 11 cases. Analyses of vertical profiles revealed higher [CO2] in the FT than in the BL in the cold sector while opposite pattern in the warm sector. Average BL-to-FT [CO2] differences are 12 and −6 ppm in the warm and cold sectors, respectively. The observational analyses presented define new metrics involving horizontal and vertical GHG contrasts across fronts during summer which will be used to evaluate simulations of GHG transport.",
keywords = "airborne atmospheric measurements, atmospheric boundary layer, cold front, free troposphere, greenhouse gases, midlatitude cyclone",
author = "Sandip Pal and Davis, {Kenneth J.} and Thomas Lauvaux and Browell, {Edward V.} and Gaudet, {Brian J.} and Stauffer, {David R.} and Obland, {Michael D.} and Yonghoon Choi and DiGangi, {Josh P.} and Sha Feng and Bing Lin and Miles, {Natasha L.} and Pauly, {Rebecca M.} and Richardson, {Scott J.} and Fuqing Zhang",
note = "Funding Information: The Atmospheric Carbon and Transport-America (ACT) project was sponsored by the National Aeronautics and Space Administration (NASA) under Award NNX15AG76G. The first author (SP) was partly supported by the NASA Grant 80NSSC19K0730. The data presented in this paper are freely available from the NASA- archive (https://www-air.larc.nasa.gov/cgi-bin/ArcView/actamerica.2016) and the ORNL data base (https://daac.ornl.gov/cgi-bin/dataset_lister.pl?p=37). We thank NASA's Airborne Sciences program, NASA Headquarters, and NASA's Earth System Science Pathfinder Program Office for their support of our mission. We would like to acknowledge the contributions of ACT collaborators, in particular, NASA project managers, scientists, and engineers for their excellent cooperation during the field campaign. Thanks are also due to the flight crews and aircraft facility groups from Wallops Flight Facility and Langley Research Center and NOAA for their outstanding work supporting these flights and measurements. We thank our colleagues Daniel Wesloh, Arkayan Samaddar, Quinn Lease, and A.J. Deng at the Pennsylvania State University for their support in weather forecasting and flight planning during the ACT summer 2016 field campaign. We also thank the ACT data management team at NASA-LaRC and ORNL in particular, Gao Chen, Michael A. Shook, Ali Aknan, Alison Boyer, Yaxing Wei, John James McNelis, and Rupesh Shrestha for their effort in performing the merges of postprocessed data sets and making data available online. Finally, we thank Dr. Douglas Chan, two anonymous reviewers, and Dr. Wouter Peters (Associate Editor) for their constructive criticisms and helpful suggestions which helped improve both technical and scientific contents of the manuscript. All the authors declare no financial conflicts of interests. Funding Information: The Atmospheric Carbon and Transport‐America (ACT) project was sponsored by the National Aeronautics and Space Administration (NASA) under Award NNX15AG76G. The first author (SP) was partly supported by the NASA Grant 80NSSC19K0730. The data presented in this paper are freely available from the NASA‐ archive ( https://www‐air.larc.nasa.gov/cgi‐bin/ArcView/actamerica.2016 ) and the ORNL data base ( https://daac.ornl.gov/cgi‐bin/dataset_lister.pl?p=37 ). We thank NASA's Airborne Sciences program, NASA Headquarters, and NASA's Earth System Science Pathfinder Program Office for their support of our mission. We would like to acknowledge the contributions of ACT collaborators, in particular, NASA project managers, scientists, and engineers for their excellent cooperation during the field campaign. Thanks are also due to the flight crews and aircraft facility groups from Wallops Flight Facility and Langley Research Center and NOAA for their outstanding work supporting these flights and measurements. We thank our colleagues Daniel Wesloh, Arkayan Samaddar, Quinn Lease, and A.J. Deng at the Pennsylvania State University for their support in weather forecasting and flight planning during the ACT summer 2016 field campaign. We also thank the ACT data management team at NASA‐LaRC and ORNL in particular, Gao Chen, Michael A. Shook, Ali Aknan, Alison Boyer, Yaxing Wei, John James McNelis, and Rupesh Shrestha for their effort in performing the merges of postprocessed data sets and making data available online. Finally, we thank Dr. Douglas Chan, two anonymous reviewers, and Dr. Wouter Peters (Associate Editor) for their constructive criticisms and helpful suggestions which helped improve both technical and scientific contents of the manuscript. All the authors declare no financial conflicts of interests. Publisher Copyright: {\textcopyright}2020. American Geophysical Union. All Rights Reserved.",
year = "2020",
month = mar,
day = "16",
doi = "10.1029/2019JD030526",
language = "English",
volume = "125",
journal = "Journal of Geophysical Research: Atmospheres",
issn = "2169-897X",
number = "5",
}