Einfluss von Gebirgswellen auf die Wasserdampfverteilung in der oberen Troposphäre und unteren Stratosphäre

Wasserdampf ist das wichtigste natürliche Treibhausgas. In dieser Arbeit liegt der Schwerpunkt auf der Untersuchung eines gebirgswelleninduzierten vertikalen Transports von Wasserdampf in die obere Troposphäre und untere Stratosphäre (UTLS). Dafür werden in einer Hotspot-Region für Schwerewellen flugzeuggetragene Messungen orographisch angeregter Gebirgswellen über den Südlichen Alpen Neuseelands ausgewertet, die im Rahmen der DEEPWAVE-Kampagne (Deep Propagating Gravity Wave Experiment) stattgefunden haben. Der aufwärts gerichtete Wasserdampftransport erstreckt sich im Höhenbereich zwischen 7,7 und 13,0 km über die thermische Tropopause hinweg. Geringe Richardson-Zahlen an Stellen hoher Gebirgswellenaktivität weisen auf das lokale Auftreten von Turbulenz knapp unterhalb der thermischen Tropopause hin. Als Konsequenz zeigt die H2O-O3-Korrelation eine verstärkte Mischung von Wasserdampf in der UTLS bei den Schwerewellenflügen gegenüber einem Flug in Hintergrundbedingungen. Die erhöhten Wasserdampfmischungsverhältnisse in der UTLS können lokal zu einem Strahlungsantrieb von mehr als 1 W m-2 führen.Water vapor is the major natural greenhouse gas. This work focuses on a mountain wave induced vertical transport of water vapor through the upper troposphere and lower stratosphere (UTLS). To this end, airborne measurements in a hot-spot region for gravity waves are investigated during an orographic mountain wave event over the Southern Alps in New Zealand. The data were collected during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign. The upward transport of water vapor from the troposphere through the thermal tropopause to the stratosphere extends over the altitude range between 7.7 and 13.0 km. Low Richardson numbers derived from dropsonde data indicate enhanced local turbulence and mixing just below the thermal tropopause. Additionally, water vapor to ozone correlations suggest stronger mixing on the mountain wave flights compared to a flight in less disturbed background conditions. The enhanced water vapor mixing ration in the UTLS caused by mountain waves could locally lead to a radiative forcing greater than 1 W m-2

Einfluss von Gebirgswellen auf die Wasserdampfverteilung in der oberen Troposphäre und unteren Stratosphäre

Wasserdampf ist das wichtigste natürliche Treibhausgas. In dieser Arbeit liegt der Schwerpunkt auf der Untersuchung eines gebirgswelleninduzierten vertikalen Transports von Wasserdampf in die obere Troposphäre und untere Stratosphäre (UTLS). Dafür werden in einer Hotspot-Region für Schwerewellen flugzeuggetragene Messungen orographisch angeregter Gebirgswellen über den Südlichen Alpen Neuseelands ausgewertet, die im Rahmen der DEEPWAVE-Kampagne (Deep Propagating Gravity Wave Experiment) stattgefunden haben. Der aufwärts gerichtete Wasserdampftransport erstreckt sich im Höhenbereich zwischen 7,7 und 13,0 km über die thermische Tropopause hinweg. Geringe Richardson-Zahlen an Stellen hoher Gebirgswellenaktivität weisen auf das lokale Auftreten von Turbulenz knapp unterhalb der thermischen Tropopause hin. Als Konsequenz zeigt die H2O-O3-Korrelation eine verstärkte Mischung von Wasserdampf in der UTLS bei den Schwerewellenflügen gegenüber einem Flug in Hintergrundbedingungen. Die erhöhten Wasserdampfmischungsverhältnisse in der UTLS können lokal zu einem Strahlungsantrieb von mehr als 1 W m-2 führen.Water vapor is the major natural greenhouse gas. This work focuses on a mountain wave induced vertical transport of water vapor through the upper troposphere and lower stratosphere (UTLS). To this end, airborne measurements in a hot-spot region for gravity waves are investigated during an orographic mountain wave event over the Southern Alps in New Zealand. The data were collected during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign. The upward transport of water vapor from the troposphere through the thermal tropopause to the stratosphere extends over the altitude range between 7.7 and 13.0 km. Low Richardson numbers derived from dropsonde data indicate enhanced local turbulence and mixing just below the thermal tropopause. Additionally, water vapor to ozone correlations suggest stronger mixing on the mountain wave flights compared to a flight in less disturbed background conditions. The enhanced water vapor mixing ration in the UTLS caused by mountain waves could locally lead to a radiative forcing greater than 1 W m-2

Einfluss von Gebirgswellen auf die Wasserdampfverteilung in der oberen Troposphäre und unteren Stratosphäre

Wasserdampf ist das wichtigste natürliche Treibhausgas. In dieser Arbeit liegt der Schwerpunkt auf der Untersuchung eines gebirgswelleninduzierten vertikalen Transports von Wasserdampf in die obere Troposphäre und untere Stratosphäre (UTLS). Dafür werden in einer Hotspot-Region für Schwerewellen flugzeuggetragene Messungen orographisch angeregter Gebirgswellen über den Südlichen Alpen Neuseelands ausgewertet, die im Rahmen der DEEPWAVE-Kampagne (Deep Propagating Gravity Wave Experiment) stattgefunden haben. Der aufwärts gerichtete Wasserdampftransport erstreckt sich im Höhenbereich zwischen 7,7 und 13,0 km über die thermische Tropopause hinweg. Geringe Richardson-Zahlen an Stellen hoher Gebirgswellenaktivität weisen auf das lokale Auftreten von Turbulenz knapp unterhalb der thermischen Tropopause hin. Als Konsequenz zeigt die H2O-O3-Korrelation eine verstärkte Mischung von Wasserdampf in der UTLS bei den Schwerewellenflügen gegenüber einem Flug in Hintergrundbedingungen. Die erhöhten Wasserdampfmischungsverhältnisse in der UTLS können lokal zu einem Strahlungsantrieb von mehr als 1 W m-2 führen.Water vapor is the major natural greenhouse gas. This work focuses on a mountain wave induced vertical transport of water vapor through the upper troposphere and lower stratosphere (UTLS). To this end, airborne measurements in a hot-spot region for gravity waves are investigated during an orographic mountain wave event over the Southern Alps in New Zealand. The data were collected during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) campaign. The upward transport of water vapor from the troposphere through the thermal tropopause to the stratosphere extends over the altitude range between 7.7 and 13.0 km. Low Richardson numbers derived from dropsonde data indicate enhanced local turbulence and mixing just below the thermal tropopause. Additionally, water vapor to ozone correlations suggest stronger mixing on the mountain wave flights compared to a flight in less disturbed background conditions. The enhanced water vapor mixing ration in the UTLS caused by mountain waves could locally lead to a radiative forcing greater than 1 W m-2

Coupling aerosols to (cirrus) clouds in the global EMAC-MADE3 aerosol–climate model

A new cloud microphysical scheme including a detailed parameterization for aerosol-driven ice formation in cirrus clouds is implemented in the global ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry–climate model and coupled to the third generation of the Modal Aerosol Dynamics model for Europe adapted for global applications (MADE3) aerosol submodel. The new scheme is able to consistently simulate three regimes of stratiform clouds – liquid, mixed-, and ice-phase (cirrus) clouds – considering the activation of aerosol particles to form cloud droplets and the nucleation of ice crystals. In the cirrus regime, it allows for the competition between homogeneous and heterogeneous freezing for the available supersaturated water vapor, taking into account different types of ice-nucleating particles, whose specific ice-nucleating properties can be flexibly varied in the model setup. The new model configuration is tuned to find the optimal set of parameters that minimizes the model deviations with respect to observations. A detailed evaluation is also performed comparing the model results for standard cloud and radiation variables with a comprehensive set of observations from satellite retrievals and in situ measurements. The performance of EMAC-MADE3 in this new coupled configuration is in line with similar global coupled models and with other global aerosol models featuring ice cloud parameterizations. Some remaining discrepancies, namely a high positive bias in liquid water path in the Northern Hemisphere and overestimated (underestimated) cloud droplet number concentrations over the tropical oceans (in the extratropical regions), which are both a common problem in these kinds of models, need to be taken into account in future applications of the model. To further demonstrate the readiness of the new model system for application studies, an estimate of the anthropogenic aerosol effective radiative forcing (ERF) is provided, showing that EMAC-MADE3 simulates a relatively strong aerosol-induced cooling but within the range reported in the Intergovernmental Panel on Climate Change (IPCC) assessments

Einfluss von Gebirgswellen auf die Wasserdampfverteilung in der oberen Troposphäre und unteren Stratosphäre

Wasserdampf ist das wichtigste natürliche Treibhausgas. In dieser Arbeit liegt der Schwerpunkt auf der Untersuchung eines gebirgswelleninduzierten vertikalen Transports von Wasserdampf in die obere Troposphäre und untere Stratosphäre (UTLS). Dafür werden in einer Hotspot-Region für Schwerewellen flugzeuggetragene Messungen orographisch angeregter Gebirgswellen über den Südlichen Alpen Neuseelands ausgewertet, die im Rahmen der DEEPWAVE-Kampagne (Deep Propagating Gravity Wave Experiment) stattgefunden haben. Der aufwärts gerichtete Wasserdampftransport erstreckt sich im Höhenbereich zwischen 7,7 und 13,0 km über die thermische Tropopause hinweg. Geringe Richardson-Zahlen an Stellen hoher Gebirgswellenaktivität weisen auf das lokale Auftreten von Turbulenz knapp unterhalb der thermischen Tropopause hin. Als Konsequenz zeigt die H2O-O3-Korrelation eine verstärkte Mischung von Wasserdampf in der UTLS bei den Schwerewellenflügen gegenüber einem Flug in Hintergrundbedingungen. Die erhöhten Wasserdampfmischungsverhältnisse in der UTLS können lokal zu einem Strahlungsantrieb von mehr als 1 W m-2 führen

Coupling aerosols to (cirrus) clouds in the global EMAC-MADE3 aerosol-climate model

A new cloud microphysical scheme including a detailed parameterization for aerosol-driven ice formation in cirrus clouds is implemented in the global ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry–climate model and coupled to the third generation of the Modal Aerosol Dynamics model for Europe adapted for global applications (MADE3) aerosol submodel. The new scheme is able to consistently simulate three regimes of stratiform clouds – liquid, mixed-, and ice-phase (cirrus) clouds – considering the activation of Aerosol particles to form cloud droplets and the nucleation of ice crystals. In the cirrus regime, it allows for the competition between homogeneous and heterogeneous freezing for the available supersaturated water vapor, taking into account different types of ice-nucleating particles, whose specific ice-nucleating properties can be flexibly varied in the model setup. The new model configuration is tuned to find the optimal set of parameters that minimizes the model deviations with respect to observations. A detailed evaluation is also performed comparing the model results for standard cloud and radiation variables with a comprehensive set of observations from satellite retrievals and in situ measurements. The performance of EMAC-MADE3 in this new coupled configuration is in line with similar global coupled models and with other global aerosol models featuring ice cloud parameterizations. Some remaining discrepancies, namely a high positive bias in liquid water path in the Northern Hemisphere and overestimated (underestimated) cloud droplet number concentrations over the tropical oceans (in the extratropical regions), which are both a common problem in these kinds of models, need to be taken into account in future applications of the model. To further demonstrate the readiness of the new model system for application studies, an estimate of the anthropogenic aerosol effective radiative forcing (ERF) is provided, showing that EMAC-MADE3 simulates a relatively strong aerosol-induced cooling but within the range reported in the Intergovernmental Panel on Climate Change (IPCC) assessments

Coupling aerosols to (cirrus) clouds in a global aerosol-climate model

The impact of aerosol on atmospheric composition and climate still represents one of the largest uncertainties in the quantification of anthropogenic climate change. This is particularly the case for modelling aerosol-cloud interactions, which requires a detailed knowledge of various processes acting on a wide range of spatial and temporal scales. While significant progress has been made in developing parameterizations for describing the aerosol activation process in liquid clouds in the framework of global models, the aerosol-induced formation of ice crystals in cirrus clouds is still poorly understood and only a few global models include explicit representations of aerosol-cloud interactions in the ice phase. This is due the high complexity of the freezing processes occurring in the ice phase, the uncertain properties of ice nucleating particles, and the competition between homogeneous and heterogeneous freezing at cirrus conditions. To tackle this issue, this study documents the implementation of a new cloud microphysical scheme, including a detailed parameterization for aerosol-driven ice formation in cirrus clouds, in the global chemistry climate model EMAC, coupled to the aerosol submodel MADE3. The new scheme is able to consistently simulate three regimes of stratiform clouds (liquid, mixed- and ice-phase/cirrus clouds), considering the activation of aerosol particles to form cloud droplets and the nucleation of ice crystals. In the cirrus regime, it allows for the competition between homogeneous and heterogeneous freezing for the available supersaturated water vapor, taking into account different types of ice-nucleating particles, whose specific ice-nucleating properties can be flexibly varied in the model setup. The new model configuration is tuned to find the optimal set of parameters that minimizes the model deviations with respect to observations. A detailed evaluation is performed comparing the model results for standard cloud and radiation variables with a comprehensive set of observations from satellite retrievals and in-situ measurements. The performance of EMAC-MADE3 in this new coupled configuration is in line with similar global coupled models and with other global aerosol models featuring ice cloud parameterizations. Some remaining discrepancies, namely a high positive bias in liquid water path in the northern hemisphere and overestimated (underestimated) cloud droplet number concentrations over the tropical oceans (in the extra-tropical regions), which are both a common problem of this kind of models, need to be taken into account in future applications of the model. To further demonstrate the readiness of the new model system for application studies, an estimate of the anthropogenic aerosol effective radiative forcing (ERF) is provided, showing that EMAC-MADE3 simulates a relatively strong aerosol-induced cooling, but within the range reported in the IPCC AR5 and in other, more recent, assessments

Chlorine partitioning in the lowermost Arctic vortex during the cold winter 2015/2016

Activated chlorine compounds in the polar winter stratosphere drive catalytic cycles that deplete ozone and methane, whose abundances are highly relevant to the evolution of global climate. The present work introduces a novel dataset of in situ measurements of relevant chlorine species in the lowermost Arctic stratosphere from the aircraft mission POLSTRACC–GW-LCYCLE–SALSA during winter 2015/2016. The major stages of chemical evolution of the lower polar vortex are presented in a consistent series of high-resolution mass spectrometric observations of HCl and ClONO2. Simultaneous measurements of CFC-12 are used to derive total inorganic chlorine (Cly) and active chlorine (ClOx). The new data highlight an altitude dependence of the pathway for chlorine deactivation in the lowermost vortex with HCl dominating below the 380 K isentropic surface and ClONO2 prevailing above. Further, we show that the Chemical Lagrangian Model of the Stratosphere (CLaMS) is generally able to reproduce the chemical evolution of the lower polar vortex chlorine budget, except for a bias in HCl concentrations. The model is used to relate local measurements to the vortex-wide evolution. The results are aimed at fostering our understanding of the climate impact of chlorine chemistry, providing new observational data to complement satellite data and assess model performance in the climate-sensitive upper troposphere and lower stratosphere region

Chlorine partitioning in the lowermost Arctic vortex during the cold winter 2015/2016

Activated chlorine compounds in the polar winter stratosphere drive catalytic cycles that deplete ozone and methane, whose abundances are highly relevant to the evolution of global climate. The present work introduces a novel dataset of in situ measurements of relevant chlorine species in the lowermost Arctic stratosphere from the aircraft mission POLSTRACC–GW-LCYCLE–SALSA during winter 2015/2016. The major stages of chemical evolution of the lower polar vortex are presented in a consistent series of high-resolution mass spectrometric observations of HCl and ClONO2. Simultaneous measurements of CFC-12 are used to derive total inorganic chlorine (Cly) and active chlorine (ClOx). The new data highlight an altitude dependence of the pathway for chlorine deactivation in the lowermost vortex with HCl dominating below the 380 K isentropic surface and ClONO2 prevailing above. Further, we show that the Chemical Lagrangian Model of the Stratosphere (CLaMS) is generally able to reproduce the chemical evolution of the lower polar vortex chlorine budget, except for a bias in HCl concentrations. The model is used to relate local measurements to the vortex-wide evolution. The results are aimed at fostering our understanding of the climate impact of chlorine chemistry, providing new observational data to complement satellite data and assess model performance in the climate-sensitive upper troposphere and lower stratosphere region