Status: this preprint has been withdrawn by the authors.
Inconsistent decadal variations between surface and free tropospheric nitrogen oxides over United States
Zhe Jiang,Helen Worden,John R. Worden,Daven K. Henze,Dylan B. A. Jones,Avelino F. Arellano,Emily V. Fischer,Liye Zhu,Kazuyuki Miyazaki,K. Folkert Boersma,and Vivienne H. Payne
Abstract. Decreases in surface emissions of nitrogen oxides (NOx = NO + NO2) in North America have led to substantial improvements in air-quality over the last several decades. Here we show that satellite observations of tropospheric nitrogen dioxide (NO2) columns over the contiguous United States (US) do not decrease after about 2009, while surface NO2 concentrations continue to decline through to the present. This divergence, if it continues, could have a substantial impact on surface air quality due to mixing of free-tropospheric air into the boundary layer. Our results show only limited contributions from local effects such as fossil fuel emissions, lightning, or instrument artifacts, but we do find a possible relationship of NO2 changes to decadal climate variability. Our analysis demonstrates that the intensity of transpacific transport is stronger in El Niño years and weaker in La Niña years, and consequently, that decadal-scale climate variability impacts the contribution of Asian emissions on North American atmospheric composition. Because of the short lifetime, it is usually believed that the direct contribution of long-range transport to tropospheric NOx distribution is limited. If our hypothesis about transported Asian emissions is correct, then this observed divergence between satellite and surface NOx could indicate mechanisms that allow for either NOx or its reservoir species to have a larger than expected effect on North American tropospheric composition. These results therefore suggest more aircraft and satellite studies to determine the possible missing processes in our understanding of the long-range transport of tropospheric NOx.
This preprint has been withdrawn.
How to cite. Jiang, Z., Worden, H., Worden, J. R., Henze, D. K., Jones, D. B. A., Arellano, A. F., Fischer, E. V., Zhu, L., Miyazaki, K., Boersma, K. F., and Payne, V. H.: Inconsistent decadal variations between surface and free tropospheric nitrogen oxides over United States, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2017-382, 2017.
Received: 29 Apr 2017 – Discussion started: 06 Jun 2017
We investigated the variation of US tropospheric NO2 in the past decade. We demonstrated significant divergence between the time variation in tropospheric NO2 columns from OMI retrievals and surface measurements. Our analysis suggests limited contributions from local effects such as fossil fuel emissions, lightning, or instrument artifacts, and indicates possible important contributions from long-range transport of Asian emissions that are modulated by ENSO.
We investigated the variation of US tropospheric NO2 in the past decade. We demonstrated...