On the importance of meteorological parameters in processes affecting the chemical composition of the tropsphere
On the importance of meteorological parameters in processes affecting the chemical composition of the tropsphere
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DissertationPrüfungsdatum
07.07.2022Datum der Veröffentlichung
22.12.2022Erstgutachter
Bott, AndreasZweitgutachter
Wahner, AndreasMetadaten
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Inhalt
Investigating the interaction of meteorology and chemistry in the troposphere is important for the identification of the processes which drive the evolution of tropospheric composition in a changing climate. It does not only improve the scientific understanding of the troposphere, which plays multiple roles in the Earth’s climate. But these investigations also help to advance our predictions of air quality. Accounting for even more realistic meteorological influences on Surface-Atmosphere interactions becomes more desirable in Earth System modelling because global warming leads to more frequent and intense weather extremes. Chemistry-Climate models deliver an essential contribution to this research as they allow covering a wide range of interacting processes whose parametrisations vary in complexity. Thereby, the investigation of tropospheric ozone (O3) is central, since enhanced O3 exposure harms humans as well as vegetation. Also, it accounts for a relevant fraction of the radiative forcing. Most importantly, O3 plays a key role in tropospheric chemistry involving radicals, nitrogen oxides (NOx=NO+NO2) and volatile organic compounds (VOC). Its evolution in the troposphere, especially at ground level, also depends significantly on exchange processes with vegetation.
Despite decades of research in this area, Chemistry-Climate models significantly overestimate tropospheric O3 in the Northern Hemisphere (NH). However, these models generally have an incomplete representation of the O3 formation and removal processes which are modulated by weather. The atmospheric chemistry model ECHAM5/MESSy (EMAC) used in this study is no exception. This thesis assesses how the inclusion of meteorological dependencies affects tropospheric chemistry and surface exchanges of O3 and its precursors and ultimately changes the model prediction of tropospheric O3 in EMAC.
First, dry deposition as a significant sink of trace gases, especially O3, is considered here. The study focuses on the uptake of trace gases by vegetation, which happens to a considerable extent via the plant’s pores (stomata). A roughly equally important uptake pathway has been proposed to be deposition to the wax covering of the leaves (cuticle). The default parameterisation for dry deposition in EMAC is hardly sensitive to local meteorological conditions (e.g., humidity) and barely represent nonstomatal deposition. In this study, a dry deposition scheme including these missing features is developed in EMAC, having an effect on O3 and its precursors. The new scheme predicts a significant enhancement of trace gas’ dry deposition, whose variation with local meteorology generally show more realistic results when compared to site measurements. However, the analysis also identifies the representation of local meteorology as a remaining significant source of uncertainty in dry deposition modelling. Additional model simulations focus on the accurate representation of tropospheric chemistry by enabling a more complex chemical mechanism and advanced biogenic VOC emissions. This investigation additionally demonstrates the importance of enhanced dry deposition of oxygenated VOCs which are sufficiently soluble to be efficiently taken up by wet surfaces. This additional non-stomatal uptake lowers the burden of many trace gases, ultimately leading to a reduction of the surface O3 model bias towards measurements. Second, the impact of water vapour forming complexes with peroxy radicals on the O3 chemistry is explored. The formation of stable complexes affects the reaction kinetics, generally leading to a weaker radical propagation. To assess its global importance, the available kinetic data for three reactions, central to O3 chemistry, is included in EMAC. Among the modified kinetics, the newly added formation channel of nitric acid (HNO3) dominates, significantly decreasing NOx and thus the formation of tropospheric O3. Accounting for water-radical complexes overall lowers the tropospheric O3 burden by 47 Tg a-1 (12 %) and the discrepancy of EMAC towards observations is significantly reduced. Third, the model representation of isoprene emissions, an important O3 precursor, is extended with a currently missing dependency on soil moisture. Accounting for the drought stress on isoprene emissions confers a higher model sensitivity to meteorology. Globally, this yields a reduction of the annual emissions by 22 % leading to a decreased O3 production. Overall, the thesis demonstrates how the inclusion of sensitivities to meteorology improve the model representation of various processes and the simulation of tropospheric O3.
Despite decades of research in this area, Chemistry-Climate models significantly overestimate tropospheric O3 in the Northern Hemisphere (NH). However, these models generally have an incomplete representation of the O3 formation and removal processes which are modulated by weather. The atmospheric chemistry model ECHAM5/MESSy (EMAC) used in this study is no exception. This thesis assesses how the inclusion of meteorological dependencies affects tropospheric chemistry and surface exchanges of O3 and its precursors and ultimately changes the model prediction of tropospheric O3 in EMAC.
First, dry deposition as a significant sink of trace gases, especially O3, is considered here. The study focuses on the uptake of trace gases by vegetation, which happens to a considerable extent via the plant’s pores (stomata). A roughly equally important uptake pathway has been proposed to be deposition to the wax covering of the leaves (cuticle). The default parameterisation for dry deposition in EMAC is hardly sensitive to local meteorological conditions (e.g., humidity) and barely represent nonstomatal deposition. In this study, a dry deposition scheme including these missing features is developed in EMAC, having an effect on O3 and its precursors. The new scheme predicts a significant enhancement of trace gas’ dry deposition, whose variation with local meteorology generally show more realistic results when compared to site measurements. However, the analysis also identifies the representation of local meteorology as a remaining significant source of uncertainty in dry deposition modelling. Additional model simulations focus on the accurate representation of tropospheric chemistry by enabling a more complex chemical mechanism and advanced biogenic VOC emissions. This investigation additionally demonstrates the importance of enhanced dry deposition of oxygenated VOCs which are sufficiently soluble to be efficiently taken up by wet surfaces. This additional non-stomatal uptake lowers the burden of many trace gases, ultimately leading to a reduction of the surface O3 model bias towards measurements. Second, the impact of water vapour forming complexes with peroxy radicals on the O3 chemistry is explored. The formation of stable complexes affects the reaction kinetics, generally leading to a weaker radical propagation. To assess its global importance, the available kinetic data for three reactions, central to O3 chemistry, is included in EMAC. Among the modified kinetics, the newly added formation channel of nitric acid (HNO3) dominates, significantly decreasing NOx and thus the formation of tropospheric O3. Accounting for water-radical complexes overall lowers the tropospheric O3 burden by 47 Tg a-1 (12 %) and the discrepancy of EMAC towards observations is significantly reduced. Third, the model representation of isoprene emissions, an important O3 precursor, is extended with a currently missing dependency on soil moisture. Accounting for the drought stress on isoprene emissions confers a higher model sensitivity to meteorology. Globally, this yields a reduction of the annual emissions by 22 % leading to a decreased O3 production. Overall, the thesis demonstrates how the inclusion of sensitivities to meteorology improve the model representation of various processes and the simulation of tropospheric O3.
Klassifikation (DDC)
500 Naturwissenschaften 540 Chemie 550 GeowissenschaftenZugehörige Publikation(en)
https://doi.org/10.5194/gmd-14-495-2021Emmerichs, Tamara: On the importance of meteorological parameters in processes affecting the chemical composition of the tropsphere. - Bonn, 2022. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-69226
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-69226
@phdthesis{handle:20.500.11811/10542,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-69226,
author = {{Tamara Emmerichs}},
title = {On the importance of meteorological parameters in processes affecting the chemical composition of the tropsphere},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2022,
month = dec,
note = {Investigating the interaction of meteorology and chemistry in the troposphere is important for the identification of the processes which drive the evolution of tropospheric composition in a changing climate. It does not only improve the scientific understanding of the troposphere, which plays multiple roles in the Earth’s climate. But these investigations also help to advance our predictions of air quality. Accounting for even more realistic meteorological influences on Surface-Atmosphere interactions becomes more desirable in Earth System modelling because global warming leads to more frequent and intense weather extremes. Chemistry-Climate models deliver an essential contribution to this research as they allow covering a wide range of interacting processes whose parametrisations vary in complexity. Thereby, the investigation of tropospheric ozone (O3) is central, since enhanced O3 exposure harms humans as well as vegetation. Also, it accounts for a relevant fraction of the radiative forcing. Most importantly, O3 plays a key role in tropospheric chemistry involving radicals, nitrogen oxides (NOx=NO+NO2) and volatile organic compounds (VOC). Its evolution in the troposphere, especially at ground level, also depends significantly on exchange processes with vegetation.
Despite decades of research in this area, Chemistry-Climate models significantly overestimate tropospheric O3 in the Northern Hemisphere (NH). However, these models generally have an incomplete representation of the O3 formation and removal processes which are modulated by weather. The atmospheric chemistry model ECHAM5/MESSy (EMAC) used in this study is no exception. This thesis assesses how the inclusion of meteorological dependencies affects tropospheric chemistry and surface exchanges of O3 and its precursors and ultimately changes the model prediction of tropospheric O3 in EMAC.
First, dry deposition as a significant sink of trace gases, especially O3, is considered here. The study focuses on the uptake of trace gases by vegetation, which happens to a considerable extent via the plant’s pores (stomata). A roughly equally important uptake pathway has been proposed to be deposition to the wax covering of the leaves (cuticle). The default parameterisation for dry deposition in EMAC is hardly sensitive to local meteorological conditions (e.g., humidity) and barely represent nonstomatal deposition. In this study, a dry deposition scheme including these missing features is developed in EMAC, having an effect on O3 and its precursors. The new scheme predicts a significant enhancement of trace gas’ dry deposition, whose variation with local meteorology generally show more realistic results when compared to site measurements. However, the analysis also identifies the representation of local meteorology as a remaining significant source of uncertainty in dry deposition modelling. Additional model simulations focus on the accurate representation of tropospheric chemistry by enabling a more complex chemical mechanism and advanced biogenic VOC emissions. This investigation additionally demonstrates the importance of enhanced dry deposition of oxygenated VOCs which are sufficiently soluble to be efficiently taken up by wet surfaces. This additional non-stomatal uptake lowers the burden of many trace gases, ultimately leading to a reduction of the surface O3 model bias towards measurements. Second, the impact of water vapour forming complexes with peroxy radicals on the O3 chemistry is explored. The formation of stable complexes affects the reaction kinetics, generally leading to a weaker radical propagation. To assess its global importance, the available kinetic data for three reactions, central to O3 chemistry, is included in EMAC. Among the modified kinetics, the newly added formation channel of nitric acid (HNO3) dominates, significantly decreasing NOx and thus the formation of tropospheric O3. Accounting for water-radical complexes overall lowers the tropospheric O3 burden by 47 Tg a-1 (12 %) and the discrepancy of EMAC towards observations is significantly reduced. Third, the model representation of isoprene emissions, an important O3 precursor, is extended with a currently missing dependency on soil moisture. Accounting for the drought stress on isoprene emissions confers a higher model sensitivity to meteorology. Globally, this yields a reduction of the annual emissions by 22 % leading to a decreased O3 production. Overall, the thesis demonstrates how the inclusion of sensitivities to meteorology improve the model representation of various processes and the simulation of tropospheric O3.},
url = {https://hdl.handle.net/20.500.11811/10542}
}
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-69226,
author = {{Tamara Emmerichs}},
title = {On the importance of meteorological parameters in processes affecting the chemical composition of the tropsphere},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2022,
month = dec,
note = {Investigating the interaction of meteorology and chemistry in the troposphere is important for the identification of the processes which drive the evolution of tropospheric composition in a changing climate. It does not only improve the scientific understanding of the troposphere, which plays multiple roles in the Earth’s climate. But these investigations also help to advance our predictions of air quality. Accounting for even more realistic meteorological influences on Surface-Atmosphere interactions becomes more desirable in Earth System modelling because global warming leads to more frequent and intense weather extremes. Chemistry-Climate models deliver an essential contribution to this research as they allow covering a wide range of interacting processes whose parametrisations vary in complexity. Thereby, the investigation of tropospheric ozone (O3) is central, since enhanced O3 exposure harms humans as well as vegetation. Also, it accounts for a relevant fraction of the radiative forcing. Most importantly, O3 plays a key role in tropospheric chemistry involving radicals, nitrogen oxides (NOx=NO+NO2) and volatile organic compounds (VOC). Its evolution in the troposphere, especially at ground level, also depends significantly on exchange processes with vegetation.
Despite decades of research in this area, Chemistry-Climate models significantly overestimate tropospheric O3 in the Northern Hemisphere (NH). However, these models generally have an incomplete representation of the O3 formation and removal processes which are modulated by weather. The atmospheric chemistry model ECHAM5/MESSy (EMAC) used in this study is no exception. This thesis assesses how the inclusion of meteorological dependencies affects tropospheric chemistry and surface exchanges of O3 and its precursors and ultimately changes the model prediction of tropospheric O3 in EMAC.
First, dry deposition as a significant sink of trace gases, especially O3, is considered here. The study focuses on the uptake of trace gases by vegetation, which happens to a considerable extent via the plant’s pores (stomata). A roughly equally important uptake pathway has been proposed to be deposition to the wax covering of the leaves (cuticle). The default parameterisation for dry deposition in EMAC is hardly sensitive to local meteorological conditions (e.g., humidity) and barely represent nonstomatal deposition. In this study, a dry deposition scheme including these missing features is developed in EMAC, having an effect on O3 and its precursors. The new scheme predicts a significant enhancement of trace gas’ dry deposition, whose variation with local meteorology generally show more realistic results when compared to site measurements. However, the analysis also identifies the representation of local meteorology as a remaining significant source of uncertainty in dry deposition modelling. Additional model simulations focus on the accurate representation of tropospheric chemistry by enabling a more complex chemical mechanism and advanced biogenic VOC emissions. This investigation additionally demonstrates the importance of enhanced dry deposition of oxygenated VOCs which are sufficiently soluble to be efficiently taken up by wet surfaces. This additional non-stomatal uptake lowers the burden of many trace gases, ultimately leading to a reduction of the surface O3 model bias towards measurements. Second, the impact of water vapour forming complexes with peroxy radicals on the O3 chemistry is explored. The formation of stable complexes affects the reaction kinetics, generally leading to a weaker radical propagation. To assess its global importance, the available kinetic data for three reactions, central to O3 chemistry, is included in EMAC. Among the modified kinetics, the newly added formation channel of nitric acid (HNO3) dominates, significantly decreasing NOx and thus the formation of tropospheric O3. Accounting for water-radical complexes overall lowers the tropospheric O3 burden by 47 Tg a-1 (12 %) and the discrepancy of EMAC towards observations is significantly reduced. Third, the model representation of isoprene emissions, an important O3 precursor, is extended with a currently missing dependency on soil moisture. Accounting for the drought stress on isoprene emissions confers a higher model sensitivity to meteorology. Globally, this yields a reduction of the annual emissions by 22 % leading to a decreased O3 production. Overall, the thesis demonstrates how the inclusion of sensitivities to meteorology improve the model representation of various processes and the simulation of tropospheric O3.},
url = {https://hdl.handle.net/20.500.11811/10542}
}
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