Tropospheric Age-of-Air: Influence of SF6 Emissions on Recent Surface Trends and Model Biases

Orbe, Clara; Waugh, Darryn W.; Montzka, Stephen; Dlugokencky, Edward J.; Strahan, Susan; Steenrod, Stephen D.; Strode, Sarah; Elkins, James W.; Hall, Bradley; Sweeney, Colm; Hintsa, Eric J.; Moore, Fred L.; Penafiel, Emma

doi:10.1029/2021JD035451

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Tropospheric Age-of-Air: Influence of SF6 Emissions on Recent Surface Trends and Model Biases

2021
By Orbe, Clara ; Waugh, Darryn W. ; Montzka, Stephen ; ...
Source: Journal of Geophysical Research: Atmospheres, 126, e2021JD035451

[PDF-3.68 MB]

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Details:

Journal Title:

Journal of Geophysical Research: Atmospheres
Personal Author:

Orbe, Clara ; Waugh, Darryn W. ; Montzka, Stephen ; Dlugokencky, Edward J. ; Strahan, Susan ; ... More +

Orbe, Clara ; Waugh, Darryn W. ; Montzka, Stephen ; Dlugokencky, Edward J. ; Strahan, Susan ; Steenrod, Stephen D. ; Strode, Sarah ; Elkins, James W. ; Hall, Bradley ; Sweeney, Colm ; Hintsa, Eric J. ; Moore, Fred L. ; Penafiel, Emma Less -
NOAA Program & Office:

OAR (Oceanic and Atmospheric Research) ; GML (Global Monitoring Laboratory) ; CIRES (Cooperative Institute for Research in Environmental Sciences)

OAR (Oceanic and Atmospheric Research) ; GML (Global Monitoring Laboratory) ; CIRES (Cooperative Institute for Research in Environmental Sciences) Less -
Description:

The mean age since air was last at the Northern Hemisphere (NH) midlatitude surface is a fundamental property of tropospheric transport. Here we approximate the mean age in terms of an urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0003 age” (urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0004), derived from surface and aircraft measurements of urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0005 that are broader in spatial scope and cover a longer time period (1997–2018) than considered previously. At the surface, urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0006 increases from near-zero values north of urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0007N to urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-00081.5 years over the Southern Hemisphere (SH) extratropics, with the largest meridional gradients occurring in the tropics. By comparison, vertical gradients in urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0009 are weak throughout, with only slight increases/decreases with height in the NH/SH. The broader spatial coverage of the measurements reveals strong variations in the seasonal cycle of urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0010 within the (sub)tropics that are weaker over the Atlantic and Pacific oceans, compared to over the Indian Ocean. Observations from 2000 to 2018 reveal that the urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0011 age at sites in the SH has been decreasing by urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-00120.12 years/dec. However, this decrease is not due to changes in transport but, rather, is likely related to changes in emissions, which have increased globally and reportedly shifted from northern midlatitudes into the subtropics. Simulations, which reproduce the urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0013 age trends, show no decreases in an age-of-air tracer, reinforcing the fact that urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0014 represents only an approximation to the mean age. Finally, the modeled urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0015 ages are older than observed, by urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-00160.3–0.4 years throughout the southern extratropics. We show that this bias is partly related to an overestimation in simulated urn:x-wiley:2169897X:media:jgrd57327:jgrd57327-math-0017 near emissions regions, likely reflecting a combination of uncertainties in emissions and model transport.
Keywords:

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Atmosphere Emissions Troposphere
Source:

Journal of Geophysical Research: Atmospheres, 126, e2021JD035451
DOI:

https://doi.org/10.1029/2021JD035451
Document Type:

Journal Article
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Submitted
Main Document Checksum:

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urn:sha256:f270b2f1a438b84ebb8f85cfcf2f7e36814d21326c45229d70800669b1b26bf5
Download URL:

https://repository.library.noaa.gov/view/noaa/44766/noaa_44766_DS1.pdf
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	ccgg	htm
	campaign	htm

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