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- Author or Editor: Linnea Avallone x
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Abstract
Recent advances in semiconductor materials and fabrication techniques have allowed the development of light-emitting diodes (LEDs) with wavelengths extending down into the UV-C region (λ < 280 nm). A new ozone photometer has been developed utilizing these novel light sources. The application of solid-state technology to the proven dual-beam UV absorption technique has improved instrument performance while reducing power consumption and weight compared to existing instrumentation. The newly developed instrument is expected to have an accuracy of 1% at surface level pressure, a resolution better than 1 ppb, and measurement rates up to 1 Hz over the range of ozone mixing ratios encountered from the earth’s surface to the middle stratosphere. Size, weight, and power consumption have also been significantly reduced, with a mass of 3 kg and a power consumption of less than 5 W. Initial development is focused on an instrument suitable for measurements from autonomous platforms and in harsh environments; however, the technology is highly adaptable to other applications.
Abstract
Recent advances in semiconductor materials and fabrication techniques have allowed the development of light-emitting diodes (LEDs) with wavelengths extending down into the UV-C region (λ < 280 nm). A new ozone photometer has been developed utilizing these novel light sources. The application of solid-state technology to the proven dual-beam UV absorption technique has improved instrument performance while reducing power consumption and weight compared to existing instrumentation. The newly developed instrument is expected to have an accuracy of 1% at surface level pressure, a resolution better than 1 ppb, and measurement rates up to 1 Hz over the range of ozone mixing ratios encountered from the earth’s surface to the middle stratosphere. Size, weight, and power consumption have also been significantly reduced, with a mass of 3 kg and a power consumption of less than 5 W. Initial development is focused on an instrument suitable for measurements from autonomous platforms and in harsh environments; however, the technology is highly adaptable to other applications.
Abstract
Over the past two decades, the National Science Foundation’s Division of Atmospheric and Geospace Sciences (AGS) has funded nearly 200 atmospheric science–related field campaigns that have included deployment of AGS-sponsored observing facilities. These projects have spanned the range from modest, single-investigator experiments to massive, multi-investigator, multiagency campaigns. They have occurred both domestically and abroad, on every continent and over most oceans. In this article, we present an analysis of some of the details about these campaigns, including such elements as deployment location and cost of the campaign, and of statistics related to the principal investigators (e.g., type and location of institution, gender, years since degree). In addition, we assess trends in field campaign cost. These results provide a retrospective view of atmospheric science field work that has been supported since 1992.
Abstract
Over the past two decades, the National Science Foundation’s Division of Atmospheric and Geospace Sciences (AGS) has funded nearly 200 atmospheric science–related field campaigns that have included deployment of AGS-sponsored observing facilities. These projects have spanned the range from modest, single-investigator experiments to massive, multi-investigator, multiagency campaigns. They have occurred both domestically and abroad, on every continent and over most oceans. In this article, we present an analysis of some of the details about these campaigns, including such elements as deployment location and cost of the campaign, and of statistics related to the principal investigators (e.g., type and location of institution, gender, years since degree). In addition, we assess trends in field campaign cost. These results provide a retrospective view of atmospheric science field work that has been supported since 1992.
Aircraft emissions impact the atmosphere in a variety of ways, including enhancing greenhouse gases, especially water vapor and carbon dioxide, in the upper troposphere and lower stratosphere, forming persistent contrails, and altering the distributions of reactive chemical species, which change the oxidative capacity of the atmosphere. This paper summarizes some recent findings related to the impacts of aircraft exhaust on the chemistry of the upper troposphere and lower stratosphere (UTLS). Of particular note are the improvements in our understanding of production of nitrogen oxides (NOx ~ NO + NO2) by lightning and of the influence of long-range transport on background abundances of reactive species. Studies have also identified gaps in our knowledge, including the behavior of HOx (OH and HO2) species at high NOx and discrepancies in measurements of water vapor in the relatively dry UTLS. Lack of detailed observations of species, such as the halogens chlorine and bromine, limits our ability to assess the role of heterogeneous chemistry on UTLS chemistry with or without the influence of aircraft exhaust. Recommendations for studies that address these issues are presented.
Aircraft emissions impact the atmosphere in a variety of ways, including enhancing greenhouse gases, especially water vapor and carbon dioxide, in the upper troposphere and lower stratosphere, forming persistent contrails, and altering the distributions of reactive chemical species, which change the oxidative capacity of the atmosphere. This paper summarizes some recent findings related to the impacts of aircraft exhaust on the chemistry of the upper troposphere and lower stratosphere (UTLS). Of particular note are the improvements in our understanding of production of nitrogen oxides (NOx ~ NO + NO2) by lightning and of the influence of long-range transport on background abundances of reactive species. Studies have also identified gaps in our knowledge, including the behavior of HOx (OH and HO2) species at high NOx and discrepancies in measurements of water vapor in the relatively dry UTLS. Lack of detailed observations of species, such as the halogens chlorine and bromine, limits our ability to assess the role of heterogeneous chemistry on UTLS chemistry with or without the influence of aircraft exhaust. Recommendations for studies that address these issues are presented.
Abstract
The University of Colorado closed-path tunable diode laser hygrometer (CLH), a new instrument for the in situ measurement of enhanced total water (eTW, the sum of water vapor and condensed water enhanced by a subisokinetic inlet), has recently been flown aboard the NASA DC-8 and WB-57F aircrafts. The CLH has the sensitivity necessary to quantify the ice water content (IWC) of extremely thin subvisual cirrus clouds (∼0.1 mg m−3), while still providing measurements over a large range of conditions typical of upper-tropospheric cirrus (up to 1 g m−3). A key feature of the CLH is its subisokinetic inlet system, which is described in detail in this paper. The enhancement and evaporation of ice particles that results from the heated subisokinetic inlet is described both analytically and based on computational fluid dynamical simulations of the flow around the aircraft. Laboratory mixtures of water vapor with an accuracy of 2%–10% (2σ) were used to calibrate the CLH over a wide range of water vapor mixing ratios (∼50–50 000 ppm) and pressures (∼100–1000 mb). The water vapor retrieval algorithm, which is based on the CLH instrument properties as well as on the spectroscopic properties of the water absorption line, accurately fits the calibration data to within the uncertainty of the calibration mixtures and instrument signal-to-noise ratio. A method for calculating cirrus IWC from the CLH enhanced total water measurement is presented. In this method, the particle enhancement factor is determined from an independent particle size distribution measurement and the size-dependent CLH inlet efficiency. It is shown that despite the potentially large uncertainty in particle size measurements, the error introduced by this method adds ∼5% error to the IWC calculation. IWC accuracy ranges from 20% at the largest IWC to 50% at small IWC (<5 mg m−3).
Abstract
The University of Colorado closed-path tunable diode laser hygrometer (CLH), a new instrument for the in situ measurement of enhanced total water (eTW, the sum of water vapor and condensed water enhanced by a subisokinetic inlet), has recently been flown aboard the NASA DC-8 and WB-57F aircrafts. The CLH has the sensitivity necessary to quantify the ice water content (IWC) of extremely thin subvisual cirrus clouds (∼0.1 mg m−3), while still providing measurements over a large range of conditions typical of upper-tropospheric cirrus (up to 1 g m−3). A key feature of the CLH is its subisokinetic inlet system, which is described in detail in this paper. The enhancement and evaporation of ice particles that results from the heated subisokinetic inlet is described both analytically and based on computational fluid dynamical simulations of the flow around the aircraft. Laboratory mixtures of water vapor with an accuracy of 2%–10% (2σ) were used to calibrate the CLH over a wide range of water vapor mixing ratios (∼50–50 000 ppm) and pressures (∼100–1000 mb). The water vapor retrieval algorithm, which is based on the CLH instrument properties as well as on the spectroscopic properties of the water absorption line, accurately fits the calibration data to within the uncertainty of the calibration mixtures and instrument signal-to-noise ratio. A method for calculating cirrus IWC from the CLH enhanced total water measurement is presented. In this method, the particle enhancement factor is determined from an independent particle size distribution measurement and the size-dependent CLH inlet efficiency. It is shown that despite the potentially large uncertainty in particle size measurements, the error introduced by this method adds ∼5% error to the IWC calculation. IWC accuracy ranges from 20% at the largest IWC to 50% at small IWC (<5 mg m−3).
The Concordiasi project is making innovative observations of the atmosphere above Antarctica. The most important goals of the Concordiasi are as follows:
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To enhance the accuracy of weather prediction and climate records in Antarctica through the assimilation of in situ and satellite data, with an emphasis on data provided by hyperspectral infrared sounders. The focus is on clouds, precipitation, and the mass budget of the ice sheets. The improvements in dynamical model analyses and forecasts will be used in chemical-transport models that describe the links between the polar vortex dynamics and ozone depletion, and to advance the under understanding of the Earth system by examining the interactions between Antarctica and lower latitudes.
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To improve our understanding of microphysical and dynamical processes controlling the polar ozone, by providing the first quasi-Lagrangian observations of stratospheric ozone and particles, in addition to an improved characterization of the 3D polar vortex dynamics. Techniques for assimilating these Lagrangian observations are being developed.
A major Concordiasi component is a field experiment during the austral springs of 2008–10. The field activities in 2010 are based on a constellation of up to 18 long-duration stratospheric super-pressure balloons (SPBs) deployed from the McMurdo station. Six of these balloons will carry GPS receivers and in situ instruments measuring temperature, pressure, ozone, and particles. Twelve of the balloons will release dropsondes on demand for measuring atmospheric parameters. Lastly, radiosounding measurements are collected at various sites, including the Concordia station.
The Concordiasi project is making innovative observations of the atmosphere above Antarctica. The most important goals of the Concordiasi are as follows:
-
To enhance the accuracy of weather prediction and climate records in Antarctica through the assimilation of in situ and satellite data, with an emphasis on data provided by hyperspectral infrared sounders. The focus is on clouds, precipitation, and the mass budget of the ice sheets. The improvements in dynamical model analyses and forecasts will be used in chemical-transport models that describe the links between the polar vortex dynamics and ozone depletion, and to advance the under understanding of the Earth system by examining the interactions between Antarctica and lower latitudes.
-
To improve our understanding of microphysical and dynamical processes controlling the polar ozone, by providing the first quasi-Lagrangian observations of stratospheric ozone and particles, in addition to an improved characterization of the 3D polar vortex dynamics. Techniques for assimilating these Lagrangian observations are being developed.
A major Concordiasi component is a field experiment during the austral springs of 2008–10. The field activities in 2010 are based on a constellation of up to 18 long-duration stratospheric super-pressure balloons (SPBs) deployed from the McMurdo station. Six of these balloons will carry GPS receivers and in situ instruments measuring temperature, pressure, ozone, and particles. Twelve of the balloons will release dropsondes on demand for measuring atmospheric parameters. Lastly, radiosounding measurements are collected at various sites, including the Concordia station.
