Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2016 Oct 4;113(40):11131-11136.
doi: 10.1073/pnas.1609919113. Epub 2016 Sep 21.

Detection of deep stratospheric intrusions by cosmogenic 35S

Mang Lin  1 , Lin Su  2 , Robina Shaheen  3 , Jimmy C H Fung  4 , Mark H Thiemens  1
Affiliations

Detection of deep stratospheric intrusions by cosmogenic 35S

Mang Lin et al. Proc Natl Acad Sci U S A. .

Abstract

The extent to which stratospheric intrusions on synoptic scales influence the tropospheric ozone (O3) levels remains poorly understood, because quantitative detection of stratospheric air has been challenging. Cosmogenic 35S mainly produced in the stratosphere has the potential to identify stratospheric air masses at ground level, but this approach has not yet been unambiguously shown. Here, we report unusually high 35S concentrations (7,390 atoms m-3; ∼16 times greater than annual average) in fine sulfate aerosols (aerodynamic diameter less than 0.95 µm) collected at a coastal site in southern California on May 3, 2014, when ground-level O3 mixing ratios at air quality monitoring stations across southern California (43 of 85) exceeded the recently revised US National Ambient Air Quality Standard (daily maximum 8-h average: 70 parts per billion by volume). The stratospheric origin of the significantly enhanced 35S level is supported by in situ measurements of air pollutants and meteorological variables, satellite observations, meteorological analysis, and box model calculations. The deep stratospheric intrusion event was driven by the coupling between midlatitude cyclones and Santa Ana winds, and it was responsible for the regional O3 pollution episode. These results provide direct field-based evidence that 35S is an additional sensitive and unambiguous tracer in detecting stratospheric air in the boundary layer and offer the potential for resolving the stratospheric influences on the tropospheric O3 level.

Keywords: National Ambient Air Quality Standard; Santa Ana wind; radioactive isotope of sulfur; stratosphere–troposphere exchange; surface ozone.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
The 35SO42− concentration in the fine aerosol sample collected on May 3, 2014 (red circle) and the comparison with annual means (gray bars; error bars stand for 1 SD) and the highest values (blue circles) measured at different sampling sites in previous studies (–20). The orange triangle represents the sample affected by the trans-Pacific transport of 35S produced from the 35Cl[n,p]35S reaction in Fukushima (25).
Fig. S1.
Fig. S1.
Fire counts observed by the MODIS during the period from April 29 to May 3, 2014 (Santa Ana period), showing the absence of large wildfires.
Fig. 2.
Fig. 2.
Distribution of ozone AQI and levels of health concern in California recorded by the US EPA on May 3, 2014 (www3.epa.gov/airdata).
Fig. 3.
Fig. 3.
Time series of hourly (A) O3, RH, and j/k measured in San Diego (the Alpine monitoring station); (B) temperature, wind speed, and direction measured in San Diego (the Kearny Mesa station); and (C) the simulated WRF stratospheric tracer and FLEXPART stratospheric O3 at the boundary layer in San Diego. The vertical black dashed lines define the period of the Santa Ana event (April 29 to May 3, 2014) based on abnormal RH and temperature.
Fig. S2.
Fig. S2.
Diurnal patterns of O3 mixing ratios on normal days (April 27 and 28 and May 4–9, 2014; black), episode days (April 29 to May 3, 2014; red), and their differences (blue).
Fig. S3.
Fig. S3.
(A) The GOME-2 vertical ozone profiles and (B) the location of the GOME-2 orbit on April 30, 2014. (C and D) The same as in A and B but on May 6, 2014. The red circle in A highlights the enhanced O3 levels induced by stratospheric intrusions. DU, Dobson unit.
Fig. 4.
Fig. 4.
Spatial distribution of the WRF stratospheric tracer at (A) 500 hPa at 0000 hours PST on April 30 and (B) 390 m above ground level at 0500 hours PST on May 1. The black star indicates the location of San Diego.
Fig. S4.
Fig. S4.
Spatial distribution of the WRF stratospheric tracer at 500 hPa at (A) 1200 hours PST on April 27, (B) 0000 hours PST on April 29, (C) 0000 hours PST on April 30, (D) 1600 hours PST on May 2, (E) 0000 hours PST on May 4, and (F) 1400 hours PST on May 5 (all 2014). The black stars indicate the location of San Diego.
Fig. 5.
Fig. 5.
Zonal cross-section of the WRF stratospheric tracer with PV (unit: PV unit) contours superimposed at 0000 hours PST on May 1, 2014. The red star indicates the location of San Diego.
Fig. S5.
Fig. S5.
Spatial distribution of the WRF stratospheric tracer at 390 m above ground level at (A) 1000 hours PST on April 30, (B) 0000 hours PST on May 1, (C) 0500 hours PST on May 1, (D) 1600 hours PST on May 2, (E) 0000 hours PST on May 4, and (F) 1400 hours PST on May 5 (all 2014). The black stars indicate the location of San Diego.
Fig. S6.
Fig. S6.
Energy spectrums of (A) the aerosol sample collected during May 3–7, 2014 and 35S standard with comparable activity, (B) 14C and 3H standards, and (C) an aerosol sample (not reported in this study) likely contaminated by 36Cl because of the incomplete removal of chlorine.
Fig. S7.
Fig. S7.
The domain setting for the WRF simulation. The black star indicates the location of San Diego.
See this image and copyright information in PMC

References

    1. McGrath JM, et al. An analysis of ozone damage to historical maize and soybean yields in the United States. Proc Natl Acad Sci USA. 2015;112(46):14390–14395. - PMC - PubMed
    1. Arneth A, et al. Terrestrial biogeochemical feedbacks in the climate system. Nat Geosci. 2010;3(8):525–532.
    1. Verstraeten WW, et al. Rapid increases in tropospheric ozone production and export from China. Nat Geosci. 2015;8(9):690–695.
    1. Skerlak B, Sprenger M, Wernli H. A global climatology of stratosphere-troposphere exchange using the ERA-Interim data set from 1979 to 2011. Atmos Chem Phys. 2014;14(2):913–937.
    1. Huang J, et al. Origin of springtime ozone enhancements in the lower troposphere over Beijing: In situ measurements and model analysis. Atmos Chem Phys. 2015;15(9):5161–5179.

Publication types

LinkOut - more resources