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- Author or Editor: Richard L. Benner x
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Abstract
The airborne applications of two recently developed analyzers for sulfur hexafluoride (SF6) to investigations of cloud top mixing and cloud seeding are described. The analyzers were developed by AeroVironment (AV) and by Washington State University (WSU). Both analyzers were capable of detecting cumulus-scale plume features. The more elaborate flow control mechanism in the AV analyzer was helpful in reducing the effects of altitude on the instrument response, while the faster response and lower baseline noise level of the WSU analyzer were necessary to detect many plume features.
A midcloud injection of SF6 was followed as it mixed through the tops of a small cumulus cloud. The tracer plume was first detected upshear, then mixed through the cloud top region as the cloud top began to collapse.
A plume of AgI cloud seeding agent mixed with SF6 was used to investigate the activation and growth of ice particles in a stratocumulus cloud which was overseeded. The SF6 tracer and ice particle plumes remained colocated during the 45 min sampling period, except for one region of ice particles which had begun to separate from the SF6 26 min after the cloud was treated. The growth of ice was limited by water vapor diffusion into the seeding plume. The measured tracer concentrations were used to estimate the fraction of the seeding nuclei which had activated and grown to detectable sizes. A maximum fraction of 54% was observed 17.5 min after seeding.
Several other applications for SF6 tracer applications are recommended.
Abstract
The airborne applications of two recently developed analyzers for sulfur hexafluoride (SF6) to investigations of cloud top mixing and cloud seeding are described. The analyzers were developed by AeroVironment (AV) and by Washington State University (WSU). Both analyzers were capable of detecting cumulus-scale plume features. The more elaborate flow control mechanism in the AV analyzer was helpful in reducing the effects of altitude on the instrument response, while the faster response and lower baseline noise level of the WSU analyzer were necessary to detect many plume features.
A midcloud injection of SF6 was followed as it mixed through the tops of a small cumulus cloud. The tracer plume was first detected upshear, then mixed through the cloud top region as the cloud top began to collapse.
A plume of AgI cloud seeding agent mixed with SF6 was used to investigate the activation and growth of ice particles in a stratocumulus cloud which was overseeded. The SF6 tracer and ice particle plumes remained colocated during the 45 min sampling period, except for one region of ice particles which had begun to separate from the SF6 26 min after the cloud was treated. The growth of ice was limited by water vapor diffusion into the seeding plume. The measured tracer concentrations were used to estimate the fraction of the seeding nuclei which had activated and grown to detectable sizes. A maximum fraction of 54% was observed 17.5 min after seeding.
Several other applications for SF6 tracer applications are recommended.
Abstract
A fast response version of the continuous SF6 analyzer originally introduced in 1976 has been developed. The new continuous analyzer has a response time constant of 0.36 s, which is 4–30 times faster than previous analyzers. The very fast response of the new analyzer allows it to be used to investigate the fundamental nature of atmospheric turbulence and diffusion processes. The new design has been thoroughly tested in laboratory and field conditions over an ambient temperature range from 4° to 40°C and an elevation range of 265 to 2130 m above sea level. The reproducibility in the response of the new analyzer was approximately ±15% over a one-month period. In automobile and aircraft sampling platforms, the reproducibility in response was less than ±12% for periods as long as 7.5 h and elevation changes exceeding 1800 m. The rate of baseline change was <1 ppt min−1 in the laboratory, <10 ppt min−1 in an automobile platform, and 15 ppt min−1 in an aircraft platform. The size, weight, and power consumption of the present analyzer have been minimized to allow for convenient mobile operation of the instrument.
Abstract
A fast response version of the continuous SF6 analyzer originally introduced in 1976 has been developed. The new continuous analyzer has a response time constant of 0.36 s, which is 4–30 times faster than previous analyzers. The very fast response of the new analyzer allows it to be used to investigate the fundamental nature of atmospheric turbulence and diffusion processes. The new design has been thoroughly tested in laboratory and field conditions over an ambient temperature range from 4° to 40°C and an elevation range of 265 to 2130 m above sea level. The reproducibility in the response of the new analyzer was approximately ±15% over a one-month period. In automobile and aircraft sampling platforms, the reproducibility in response was less than ±12% for periods as long as 7.5 h and elevation changes exceeding 1800 m. The rate of baseline change was <1 ppt min−1 in the laboratory, <10 ppt min−1 in an automobile platform, and 15 ppt min−1 in an aircraft platform. The size, weight, and power consumption of the present analyzer have been minimized to allow for convenient mobile operation of the instrument.
Abstract
Half of Earth’s land surface has been altered by human activities, creating various consequences on the climate and weather systems at local to global scales, which in turn affect a myriad of land surface processes and the adaptation behaviors. This study reviews the status and major knowledge gaps in the interactions of land and atmospheric changes and present 11 grand challenge areas for the scientific research and adaptation community in the coming decade. These land-cover and land-use change (LCLUC)-related areas include 1) impacts on weather and climate, 2) carbon and other biogeochemical cycles, 3) biospheric emissions, 4) the water cycle, 5) agriculture, 6) urbanization, 7) acclimation of biogeochemical processes to climate change, 8) plant migration, 9) land-use projections, 10) model and data uncertainties, and, finally, 11) adaptation strategies. Numerous studies have demonstrated the effects of LCLUC on local to global climate and weather systems, but these putative effects vary greatly in magnitude and even sign across space, time, and scale and thus remain highly uncertain. At the same time, many challenges exist toward improved understanding of the consequences of atmospheric and climate change on land process dynamics and services. Future effort must improve the understanding of the scale-dependent, multifaceted perturbations and feedbacks between land and climate changes in both reality and models. To this end, one critical cross-disciplinary need is to systematically quantify and better understand measurement and model uncertainties. Finally, LCLUC mitigation and adaptation assessments must be strengthened to identify implementation barriers, evaluate and prioritize opportunities, and examine how decision-making processes work in specific contexts.
Abstract
Half of Earth’s land surface has been altered by human activities, creating various consequences on the climate and weather systems at local to global scales, which in turn affect a myriad of land surface processes and the adaptation behaviors. This study reviews the status and major knowledge gaps in the interactions of land and atmospheric changes and present 11 grand challenge areas for the scientific research and adaptation community in the coming decade. These land-cover and land-use change (LCLUC)-related areas include 1) impacts on weather and climate, 2) carbon and other biogeochemical cycles, 3) biospheric emissions, 4) the water cycle, 5) agriculture, 6) urbanization, 7) acclimation of biogeochemical processes to climate change, 8) plant migration, 9) land-use projections, 10) model and data uncertainties, and, finally, 11) adaptation strategies. Numerous studies have demonstrated the effects of LCLUC on local to global climate and weather systems, but these putative effects vary greatly in magnitude and even sign across space, time, and scale and thus remain highly uncertain. At the same time, many challenges exist toward improved understanding of the consequences of atmospheric and climate change on land process dynamics and services. Future effort must improve the understanding of the scale-dependent, multifaceted perturbations and feedbacks between land and climate changes in both reality and models. To this end, one critical cross-disciplinary need is to systematically quantify and better understand measurement and model uncertainties. Finally, LCLUC mitigation and adaptation assessments must be strengthened to identify implementation barriers, evaluate and prioritize opportunities, and examine how decision-making processes work in specific contexts.
Abstract
The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe.
Abstract
The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe.
