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  • 1
    Online Resource
    Online Resource
    Dynamically controlled ozone decline in the tropical mid-stratosphere observed by SCIAMACHY
    Copernicus GmbH ; 2019
    In:  Atmospheric Chemistry and Physics Vol. 19, No. 2 ( 2019-01-22), p. 767-783
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 19, No. 2 ( 2019-01-22), p. 767-783
    Abstract: Abstract. Despite the recently reported beginning of a recovery in global stratospheric ozone (O3), an unexpected O3 decline in the tropical mid-stratosphere (around 30–35 km altitude) was observed in satellite measurements during the first decade of the 21st century. We use SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) measurements for the period 2004–2012 to confirm the significant O3 decline. The SCIAMACHY observations show that the decrease in O3 is accompanied by an increase in NO2. To reveal the causes of these observed O3 and NO2 changes, we performed simulations with the TOMCAT 3-D chemistry-transport model (CTM) using different chemical and dynamical forcings. For the 2004–2012 time period, the TOMCAT simulations reproduce the SCIAMACHY-observed O3 decrease and NO2 increase in the tropical mid-stratosphere. The simulations suggest that the positive changes in NO2 (around 7 % decade−1) are due to similar positive changes in reactive odd nitrogen (NOy), which are a result of a longer residence time of the source gas N2O and increased production via N2O + O(1D). The model simulations show a negative change of 10 % decade−1 in N2O that is most likely due to variations in the deep branch of the Brewer–Dobson Circulation (BDC). Interestingly, modelled annual mean “age of air” (AoA) does not show any significant changes in transport in the tropical mid-stratosphere during 2004–2012. However, further analysis of model results demonstrates significant seasonal variations. During the autumn months (September–October) there are positive AoA changes that imply transport slowdown and a longer residence time of N2O allowing for more conversion to NOy, which enhances O3 loss. During winter months (January–February) there are negative AoA changes, indicating faster N2O transport and less NOy production. Although the variations in AoA over a year result in a statistically insignificant linear change, non-linearities in the chemistry–transport interactions lead to a statistically significant negative N2O change.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-19-767-2019
    DOI: 10.5194/acp-19-767-2019-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 2
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    Online Resource
    Increased aerosol content in the atmosphere over Ukraine during summer 2010
    Copernicus GmbH ; 2018
    In:  Atmospheric Measurement Techniques Vol. 11, No. 4 ( 2018-04-12), p. 2101-2118
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 11, No. 4 ( 2018-04-12), p. 2101-2118
    Abstract: Abstract. In this paper we assessed the influence of biomass burning during forest fires throughout summer (1 June–31 August) 2010 on aerosol abundance, dynamics, and its properties over Ukraine. We also considered influences and effects over neighboring countries: European Russia, Estonia, Belarus, Poland, Moldova, and Romania. We used MODIS satellite instrument data to study fire distribution. We also used ground-based remote measurements from the international sun photometer network AERONET plus MODIS and CALIOP satellite instrument data to determine the aerosol content and optical properties in the atmosphere over Eastern Europe. We applied the HYSPLIT model to investigate atmospheric dynamics and model pathways of particle transport. As with previous studies, we found that the highest aerosol content was observed over Moscow in the first half of August 2010 due to the proximity of the most active fires. Large temporal variability of the aerosol content with pronounced pollution peaks during 7–17 August was observed at the Ukrainian (Kyiv and Sevastopol), Belarusian (Minsk), Estonian (Toravere), and Romanian (Bucharest) AERONET sites. We analyzed aerosol spatiotemporal distribution over Ukraine using MODIS AOD 550 nm and further compared with the Kyiv AERONET site sun photometer measurements; we also compared CALIOP AOD 532 nm with MODIS AOD data. We analyzed vertical distribution of aerosol extinction at 532 nm, retrieved from CALIOP measurements, for the territory of Ukraine at locations where high AOD values were observed during intense fires. We estimated the influence of fires on the spectral single scattering albedo, size distribution, and complex refractive indices using Kyiv AERONET measurements performed during summer 2010. In this study we showed that the maximum AOD in the atmosphere over Ukraine recorded in summer 2010 was caused by particle transport from the forest fires in Russia. Those fires caused the highest AOD 500 nm over the Kyiv site, which in August 2010 exceeded multiannual monthly mean for the entire observational period (2008–2016, excluding 2010) by a factor of 2.2. Also, the influence of fires resulted in a change of the particle microphysics in the polluted regions.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    URL: Article
    DOI: 10.5194/amt-11-2101-2018
    DOI: 10.5194/amt-11-2101-2018-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2505596-3
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  • 3
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    Online Resource
    Evaluating Causal Arctic‐Midlatitude Teleconnections in CMIP6
    American Geophysical Union (AGU) ; 2023
    In:  Journal of Geophysical Research: Atmospheres Vol. 128, No. 17 ( 2023-09-16)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 128, No. 17 ( 2023-09-16)
    Abstract: The robustness of Arctic‐midlatitude teleconnections is evaluated by applying causal discovery to observations and CMIP6 simulations Observations, CMIP6 historical and SSP5‐8.5 simulations do not robustly show Arctic‐midlatitude links arising from sea ice variability CMIP6 SSP5‐8.5 simulations predict a more robust link between poleward eddy heat flux and Aleutian Low toward the end of the 21st century
    Type of Medium: Online Resource
    ISSN: 2169-897X , 2169-8996
    URL: Article
    DOI: 10.1029/2022JD037978
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2023
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 2969341-X
    SSG: 16,13
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  • 4
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    Online Resource
    Regime-oriented causal model evaluation of Atlantic–Pacific teleconnections in CMIP6
    Copernicus GmbH ; 2023
    In:  Earth System Dynamics Vol. 14, No. 2 ( 2023-03-21), p. 309-344
    Details
    In: Earth System Dynamics, Copernicus GmbH, Vol. 14, No. 2 ( 2023-03-21), p. 309-344
    Abstract: Abstract. The climate system and its spatio-temporal changes are strongly affected by modes of long-term internal variability, like the Pacific decadal variability (PDV) and the Atlantic multidecadal variability (AMV). As they alternate between warm and cold phases, the interplay between PDV and AMV varies over decadal to multidecadal timescales. Here, we use a causal discovery method to derive fingerprints in the Atlantic–Pacific interactions and to investigate their phase-dependent changes. Dependent on the phases of PDV and AMV, different regimes with characteristic causal fingerprints are identified in reanalyses in a first step. In a second step, a regime-oriented causal model evaluation is performed to evaluate the ability of models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) in representing the observed changing interactions between PDV, AMV and their extra-tropical teleconnections. The causal graphs obtained from reanalyses detect a direct opposite-sign response from AMV to PDV when analyzing the complete 1900–2014 period and during several defined regimes within that period, for example, when AMV is going through its negative (cold) phase. Reanalyses also demonstrate a same-sign response from PDV to AMV during the cold phase of PDV. Historical CMIP6 simulations exhibit varying skill in simulating the observed causal patterns. Generally, large-ensemble (LE) simulations showed better network similarity when PDV and AMV were out of phase compared to other regimes. Also, the two largest ensembles (in terms of number of members) were found to contain realizations with similar causal fingerprints to observations. For most regimes, these same models showed higher network similarity when compared to each other. This work shows how causal discovery on LEs complements the available diagnostics and statistical metrics of climate variability to provide a powerful tool for climate model evaluation.
    Type of Medium: Online Resource
    ISSN: 2190-4987
    URL: Article
    DOI: 10.5194/esd-14-309-2023
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2578793-7
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