Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> Injections
Climate modification by stratospheric SO<sub>2</sub> injections, to form sulfate aerosols, may alter the spectral and angular distributions of the solar ultraviolet and visible radiation that reach the Earth’s surface, with potential consequences to environmental photobiology a...
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| Format: | Article |
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MDPI AG
2018-11-01
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| Series: | Atmosphere |
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| Online Access: | https://www.mdpi.com/2073-4433/9/11/432 |
| _version_ | 1811234444399345664 |
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| author | Sasha Madronich Simone Tilmes Ben Kravitz Douglas G. MacMartin Jadwiga H. Richter |
| author_facet | Sasha Madronich Simone Tilmes Ben Kravitz Douglas G. MacMartin Jadwiga H. Richter |
| author_sort | Sasha Madronich |
| collection | DOAJ |
| description | Climate modification by stratospheric SO<sub>2</sub> injections, to form sulfate aerosols, may alter the spectral and angular distributions of the solar ultraviolet and visible radiation that reach the Earth’s surface, with potential consequences to environmental photobiology and photochemistry. We used modeling results from the CESM1(WACCM) stratospheric aerosol geoengineering large ensemble (GLENS) project, following the RCP8.5 emission scenario, and one geoengineering experiment with SO<sub>2</sub> injections in the stratosphere, designed to keep surface temperatures at 2020 levels. Zonally and monthly averaged vertical profiles of O<sub>3</sub>, SO<sub>2</sub>, and sulfate aerosols, at 30 N and 70 N, served as input into a radiative transfer model, to compute biologically active irradiances for DNA damage (<i>i</i><sub>DNA</sub>), UV index (UVI), photosynthetically active radiation (PAR), and two key tropospheric photodissociation coefficients (<i>j</i><sub>O1D</sub> for O<sub>3</sub> + hν (λ < 330 nm) → O(<sup>1</sup>D) + O<sub>2</sub>; and <i>j</i><sub>NO2</sub> for NO<sub>2</sub> + hν (λ < 420 nm) → O(<sup>3</sup>P) + NO). We show that the geoengineering scenario is accompanied by substantial reductions in UV radiation. For example, comparing March 2080 to March 2020, <i>i</i><sub>DNA</sub> decreased by 25% to 29% in the subtropics (30 N) and by 26% to 33% in the polar regions (70 N); UVI decreased by 19% to 20% at 30 N and 23% to 26% at 70 N; and <i>j</i><sub>O1D</sub> decreased by 22% to 24% at 30 N and 35% to 40% at 70 N, with comparable contributions from sulfate scattering and stratospheric O<sub>3</sub> recovery. Different responses were found for processes that depend on longer UV and visible wavelengths, as these are minimally affected by ozone; PAR and <i>j</i><sub>NO2</sub> were only slightly lower (9⁻12%) at 30 N, but much lower at 70 N (35⁻40%). Similar reductions were estimated for other months (June, September, and December). Large increases in the PAR diffuse-direct ratio occurred in agreement with previous studies. Absorption by SO<sub>2</sub> gas had a small (~1%) effect on <i>j</i><sub>O1D</sub>, <i>i</i><sub>DNA</sub>, and UVI, and no effect on <i>j</i><sub>NO2</sub> and PAR. |
| first_indexed | 2024-04-12T11:37:29Z |
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| issn | 2073-4433 |
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| last_indexed | 2024-04-12T11:37:29Z |
| publishDate | 2018-11-01 |
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| spelling | doaj.art-57d260fc99ad4dd78b0d2b39a8070aab2022-12-22T03:34:48ZengMDPI AGAtmosphere2073-44332018-11-0191143210.3390/atmos9110432atmos9110432Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> InjectionsSasha Madronich0Simone Tilmes1Ben Kravitz2Douglas G. MacMartin3Jadwiga H. Richter4Atmospheric Chemistry, Observations, and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO 80307, USAAtmospheric Chemistry, Observations, and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO 80307, USAAtmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99352, USAMechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USAClimate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO 80307, USAClimate modification by stratospheric SO<sub>2</sub> injections, to form sulfate aerosols, may alter the spectral and angular distributions of the solar ultraviolet and visible radiation that reach the Earth’s surface, with potential consequences to environmental photobiology and photochemistry. We used modeling results from the CESM1(WACCM) stratospheric aerosol geoengineering large ensemble (GLENS) project, following the RCP8.5 emission scenario, and one geoengineering experiment with SO<sub>2</sub> injections in the stratosphere, designed to keep surface temperatures at 2020 levels. Zonally and monthly averaged vertical profiles of O<sub>3</sub>, SO<sub>2</sub>, and sulfate aerosols, at 30 N and 70 N, served as input into a radiative transfer model, to compute biologically active irradiances for DNA damage (<i>i</i><sub>DNA</sub>), UV index (UVI), photosynthetically active radiation (PAR), and two key tropospheric photodissociation coefficients (<i>j</i><sub>O1D</sub> for O<sub>3</sub> + hν (λ < 330 nm) → O(<sup>1</sup>D) + O<sub>2</sub>; and <i>j</i><sub>NO2</sub> for NO<sub>2</sub> + hν (λ < 420 nm) → O(<sup>3</sup>P) + NO). We show that the geoengineering scenario is accompanied by substantial reductions in UV radiation. For example, comparing March 2080 to March 2020, <i>i</i><sub>DNA</sub> decreased by 25% to 29% in the subtropics (30 N) and by 26% to 33% in the polar regions (70 N); UVI decreased by 19% to 20% at 30 N and 23% to 26% at 70 N; and <i>j</i><sub>O1D</sub> decreased by 22% to 24% at 30 N and 35% to 40% at 70 N, with comparable contributions from sulfate scattering and stratospheric O<sub>3</sub> recovery. Different responses were found for processes that depend on longer UV and visible wavelengths, as these are minimally affected by ozone; PAR and <i>j</i><sub>NO2</sub> were only slightly lower (9⁻12%) at 30 N, but much lower at 70 N (35⁻40%). Similar reductions were estimated for other months (June, September, and December). Large increases in the PAR diffuse-direct ratio occurred in agreement with previous studies. Absorption by SO<sub>2</sub> gas had a small (~1%) effect on <i>j</i><sub>O1D</sub>, <i>i</i><sub>DNA</sub>, and UVI, and no effect on <i>j</i><sub>NO2</sub> and PAR.https://www.mdpi.com/2073-4433/9/11/432geoengineeringsulfate aerosolsstratospherestratospheric ozoneultraviolet radiationerythemal radiationphotolysis coefficientsphotosynthetically active radiation (PAR)direct-diffuse ratio |
| spellingShingle | Sasha Madronich Simone Tilmes Ben Kravitz Douglas G. MacMartin Jadwiga H. Richter Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> Injections Atmosphere geoengineering sulfate aerosols stratosphere stratospheric ozone ultraviolet radiation erythemal radiation photolysis coefficients photosynthetically active radiation (PAR) direct-diffuse ratio |
| title | Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> Injections |
| title_full | Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> Injections |
| title_fullStr | Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> Injections |
| title_full_unstemmed | Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> Injections |
| title_short | Response of Surface Ultraviolet and Visible Radiation to Stratospheric SO<sub>2</sub> Injections |
| title_sort | response of surface ultraviolet and visible radiation to stratospheric so sub 2 sub injections |
| topic | geoengineering sulfate aerosols stratosphere stratospheric ozone ultraviolet radiation erythemal radiation photolysis coefficients photosynthetically active radiation (PAR) direct-diffuse ratio |
| url | https://www.mdpi.com/2073-4433/9/11/432 |
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