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  • American Meteorological Society  (3)
  • 1
    Online Resource
    Online Resource
    Stratospheric Ozone Changes Damp the CO2-Induced Acceleration of the Brewer–Dobson Circulation
    American Meteorological Society ; 2023
    In:  Journal of Climate Vol. 36, No. 10 ( 2023-05-15), p. 3305-3320
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 36, No. 10 ( 2023-05-15), p. 3305-3320
    Abstract: The increase of atmospheric CO 2 concentrations changes the atmospheric temperature distribution, which in turn affects the circulation. A robust circulation response to CO 2 forcing is the strengthening of the stratospheric Brewer–Dobson circulation (BDC), with associated consequences for transport of trace gases such as ozone. Ozone is further affected by the CO 2 -induced stratospheric cooling via the temperature dependency of ozone chemistry. These ozone changes in turn influence stratospheric temperatures and thereby modify the CO 2 -induced circulation changes. In this study, we perform dedicated model simulations to quantify the modification of the circulation response to CO 2 forcing by stratospheric ozone. Specifically, we compare simulations of the atmosphere with preindustrial and with quadrupled CO 2 climate conditions, in which stratospheric ozone is held fixed or is adapted to the new climate state. The results of the residual circulation and mean age of air show that ozone changes damp the CO 2 -induced BDC increase by up to 20%. This damping of the BDC strengthening is linked to an ozone-induced relative enhancement of the meridional temperature gradient in the lower stratosphere in summer, thereby leading to stronger stratospheric easterlies that suppress wave propagation. Additionally, we find a systematic weakening of the polar vortices in winter and spring. In the Southern Hemisphere, ozone reduces the CO 2 -induced delay of the final warming date by 50%. Significance Statement A robust circulation response to enhanced CO 2 is the strengthening of the equator-to-pole circulation in the stratosphere, the so-called Brewer–Dobson circulation (BDC), which affects the ozone layer by tracer transport. This in turn alters stratospheric temperatures and thereby modifies the stratospheric circulation. In the present study, we perform model experiments to quantify the ozone-induced circulation changes caused by quadrupled CO 2 concentrations. The results show that ozone changes damp the CO 2 -induced BDC strengthening due to radiative effects of the redistributed ozone layer by enhanced CO 2 . These ozone modifications lead to strengthened stratospheric easterlies in summer and decelerated westerlies in winter and spring. Moreover, the ozone changes reduce the CO 2 -induced delay of the polar vortex break down date in the Southern Hemisphere.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    URL: Article
    DOI: 10.1175/JCLI-D-22-0512.1
    DOI: 10.1175/JCLI-D-22-0512.s1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Evaluating the Relationship between Interannual Variations in the Antarctic Ozone Hole and Southern Hemisphere Surface Climate in Chemistry–Climate Models
    American Meteorological Society ; 2019
    In:  Journal of Climate Vol. 32, No. 11 ( 2019-06-01), p. 3131-3151
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 32, No. 11 ( 2019-06-01), p. 3131-3151
    Abstract: Studies have recently reported statistically significant relationships between observed year-to-year spring Antarctic ozone variability and the Southern Hemisphere annular mode and surface temperatures in spring–summer. This study investigates whether current chemistry–climate models (CCMs) can capture these relationships, in particular, the connection between November total column ozone (TCO) and Australian summer surface temperatures, where years with anomalously high TCO over the Antarctic polar cap tend to be followed by warmer summers. The interannual ozone–temperature teleconnection is examined over the historical period in the observations and simulations from the Whole Atmosphere Community Climate Model (WACCM) and nine other models participating in the Chemistry–Climate Model Initiative (CCMI). There is a systematic difference between the WACCM experiments forced with prescribed observed sea surface temperatures (SSTs) and those with an interactive ocean. Strong correlations between TCO and Australian temperatures are only obtained for the uncoupled experiment, suggesting that the SSTs could be important for driving both variations in Australian temperatures and the ozone hole, with no causal link between the two. Other CCMI models also tend to capture this relationship with more fidelity when driven by observed SSTs, although additional research and targeted modeling experiments are required to determine causality and further explore the role of model biases and observational uncertainty. The results indicate that CCMs can reproduce the relationship between spring ozone and summer Australian climate reported in observational studies, suggesting that incorporating ozone variability could improve seasonal predictions; however, more work is required to understand the difference between the coupled and uncoupled simulations.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-18-0273.1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2019
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Cleaner Skies during the COVID-19 Lockdown
    American Meteorological Society ; 2022
    In:  Bulletin of the American Meteorological Society Vol. 103, No. 8 ( 2022-08), p. E1796-E1827
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 103, No. 8 ( 2022-08), p. E1796-E1827
    Abstract: During spring 2020, the COVID-19 pandemic caused massive reductions in emissions from industry and ground and airborne transportation. To explore the resulting atmospheric composition changes, we conducted the BLUESKY campaign with two research aircraft and measured trace gases, aerosols, and cloud properties from the boundary layer to the lower stratosphere. From 16 May to 9 June 2020, we performed 20 flights in the early COVID-19 lockdown phase over Europe and the Atlantic Ocean. We found up to 50% reductions in boundary layer nitrogen dioxide concentrations in urban areas from GOME-2B satellite data, along with carbon monoxide reductions in the pollution hot spots. We measured 20%–70% reductions in total reactive nitrogen, carbon monoxide, and fine mode aerosol concentration in profiles over German cities compared to a 10-yr dataset from passenger aircraft. The total aerosol mass was significantly reduced below 5 km altitude, and the organic aerosol fraction also aloft, indicative of decreased organic precursor gas emissions. The reduced aerosol optical thickness caused a perceptible shift in sky color toward the blue part of the spectrum (hence BLUESKY) and increased shortwave radiation at the surface. We find that the 80% decline in air traffic led to substantial reductions in nitrogen oxides at cruise altitudes, in contrail cover, and in resulting radiative forcing. The light extinction and depolarization by cirrus were also reduced in regions with substantially decreased air traffic. General circulation–chemistry model simulations indicate good agreement with the measurements when applying a reduced emission scenario. The comprehensive BLUESKY dataset documents the major impact of anthropogenic emissions on the atmospheric composition.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    DOI: 10.1175/BAMS-D-21-0012.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2022
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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