50. ATMOSPHERIC MEASUREMENT TECHNOLOGY
World-wide energy production is modifying the chemical composition of the atmosphere and is linked with environmental degradation and human health problems. The radiative transfer properties of the atmosphere may be changing as well. The changes in chemical composition will require the development of atmospheric measurement techniques with high accuracy and/or time stability, in order to support a strategy of sustainable and pollution-free energy development for the future. Innovative measurement technology also will be needed, as input and comparison data, for models used to assess the radiative impacts of atmospheric components. Grant applications must propose Phase I bench tests of critical technologies with respect to the subtopics that follow. (“Critical technologies” refer to components, materials, equipment, or processes that overcome significant limitations to current capabilities.) For example, grant applications proposing only computer modeling without physical testing will be considered non-responsive. Grant applications also should describe the purpose and benefits of any proposed teaming arrangements with government laboratories or universities. Applications submitted to any of the subtopics should support claims of commercial potential for proposed technologies (e.g., endorsements from relevant industrial sectors, market analysis, or identification of potential spin-offs). Grant applications are sought only in the following subtopics:
a. Measurements of the Chemical Composition of Atmospheric Aerosols—There is a need to develop improved measurement methods to characterize the bulk and the size-resolved chemical composition of ambient aerosols in real time, particularly carbonaceous aerosols. Improved measurements would facilitate the identification of the origin of aerosols, i.e. primary versus secondary and fossil fuel versus biogenic. Also, these measurements could help elucidate how aerosol particles are processed in the atmosphere by chemical reactions and by clouds, and how their hygroscopic properties change as they age. This information is important because relatively little is known about organic and absorbing particles, which are abundant in many locations in the atmosphere. In particular, there is a need for instruments suitable for real-time measurements of the composition of particles at the molecular level. Although recent advances have led to the development of new instruments, such as particle mass spectrometers and single particle analyzers, these instruments have important limitations in their ability to quantify black carbon vs. organic carbon, provide speciation of refractory and volatile organic compounds, and calibrate both organic and inorganic components. Further, instruments that otherwise would be suitable for ground-based operation often have limitations (size, weight, power, stability, etc.) that limit their application for in situ measurements, where critical atmospheric processes actually occur (e.g., in or near clouds).
Therefore, in order to better understand the chemical composition of atmospheric aerosols, grant applications are sought to develop improved instruments, or entirely new measurement methods, that provide: (1) quantifiable results over a wide range of compounds – a problem for laser ablation aerosol mass spectrometer methods; (2) measurements over a range of volatility so that dust, carbon, and salt are detectable – a problem for thermal decomposition aerosol mass spectrometers; (3) speciation of individual organics, including those containing oxygen, nitrogen, and sulfur; (4) identification of elemental carbon and other carbonaceous material, so that the makeup of the absorbing fraction is known; (5) measurements with high time resolution – an inherent problem with filter techniques; (6) identification of source markers, such as isotopic abundances in aerosols; (7) the ability to probe the chemical composition of aerosol surfaces; and/or (8) improved measurements of aerosol chemical composition from airborne platforms.
Questions - contact Ashley D. Williamson (ashley.williamson@science.doe.gov)
b. Instrumentation for Characterizing Atmospheric Aerosols—In addition to chemical composition, improved or new instruments are needed for the measurement and understanding of other characteristics of atmospheric aerosols. Instruments that are suitable for use on airborne platforms are of specific interest.
(1) Aerosol precursors. Improvements in understanding gas phase chemistry are needed to further understand the evolution of aerosols in clouds. For example, gas phase measurements of H2SO4, a major aerosol precursor, have revealed a wealth of new information in the last decade. To make further progress, grant applications are sought to develop instruments that can make fast measurements of NH3, ion clusters, and gas phase organics, substances that might either condense or dissolve into preexisting aerosols or cloud droplets. Of particular interest are measurements that can further segregate and organic substances into various classes – for example, segregation by volatility, water solubility, chemical class (alkanes, alkenes, aromatics, aldehydes, etc.) oxidation state, or functional groupings (nitrates, peroxides, etc.). Grant applications should identify any special instrument capabilities and describe the added value that they provide.
(2) Aerosol absorption. The aerosol absorption coefficient, together with the aerosol scattering coefficient, determines the single-scattering albedo. This key aerosol property, along with the factors that contribute to it, are critical for determining heating rates and climate forcing by aerosols. Therefore, grant applications are sought to develop reliable instruments for the in situ measurement of the single-scattering albedo for particles containing black and organic carbon, dust, and minerals. The measurements must cover the solar wavelengths (UV, visible, and near infrared), must not alter aerosol properties, and must address the influence of relative humidity. In situ measurements on particles in unperturbed local humidity environments must be combined with simultaneous measurement of local temperature and humidity. Of particular interest are instruments that can measure the aerosol optical properties over a range of known humidity states.
(3) Aerosol size distributions. Knowledge of particle size distribution is essential for describing both direct and indirect radiative forcing by aerosols. However, current techniques for determining these distributions are often ambiguous, because of the assumption that the particles are spherical. In particular, the optical techniques most often used in the 0.5-10 µm size range have inherent problems. Therefore, grant applications are sought for techniques to determine the size distribution of ambient aerosols, in the 0.5-10 µm size range, that are not based on optical properties. The techniques must address the influence of relative humidity, as described in item (2) above, and, as appropriate, must simultaneously provide calculated values of such properties as mass, area (extinction), and number.
Questions - contact Ashley D. Williamson (ashley.williamson@science.doe.gov)
c. In-Situ Measurement of Cloud Properties with Large Sample Volumes—The response of clouds to climate change (the so-called "cloud feedback" problem) remains poorly understood, from both a measurement and a modeling point of view [Stephens, 2005]. Currently, there is a huge gap in the spatial scale between in situ measurements of cloud properties – typically from aircraft and balloons whose instruments have sample volumes on the order of cubic centimeters – and remote sensing retrievals of cloud properties – which have sample volumes ranging from tens of cubic meters (using radar and lidar) to thousands of cubic meters (using satellites). The most acute feature of this gap is that the in situ measurements at a particular point provide no information on the vertical distribution above and below that point, whereas the remote sensing retrievals typically provide instantaneous vertically-resolved information. Because clouds are inhomogeneous down to centimeter scales, simple assumptions of homogeneity, in order to scale up the in situ measurements, are certainly false. Consequently, there is a complete lack of comparability between the in situ measurements and remote retrievals. In addition, clouds evolve considerably in the course of one minute, and thus methods which are slow in time (such as a balloon ascending, or an aircraft ascending or descending) fail to capture the instantaneous state seen by remote sensing methods. Thus, there is a great need for in situ measurements which have fast vertical reach and much larger sample volumes, ranging from cubic meters to hundreds of cubic meters, in order to allow meaningful comparisons with surface and satellite retrievals of cloud properties. Without confidence in those surface and satellite retrievals, which are our only way to extend our reach to the whole planet, it is impossible to make progress on key global change issues concerning cloud feedbacks on global warming.
Therefore, grant applications are sought to develop instruments to measure cloud properties in situ, on scales ranging from cubic meters to hundreds of cubic meters, with particular emphasis on fast vertical profiling above and below the in situ platform. An example of such an instrument can be seen in Evans, et al. (2003). Measurements of the following cloud properties, in order of decreasing priority, are of particular interest for cloud-climate applications: (a) extinction coefficient at one or more wavelengths in the solar spectrum away from strong water vapor absorption bands; (b) total water content (liquid plus ice); (c) liquid and ice water content separately; (d) effective radius, defined as the ratio of the 3rd to the 2nd moment of the drop size distribution; (e) absorption coefficient or single-scattering albedo at one or more wavelengths in the solar spectrum away from strong water vapor absorption bands; (f) the scattering phase function for ice clouds; (g) the drizzle and precipitation fraction of the total condensed water content; (h) the supersaturation; and (i) the dispersion, a measure of the width of the drop size distribution. Grant applications also must account for the need to miniaturize the proposed instrumentation (in terms of both size and weight) for placement on aerial measurement platforms (e.g., aircraft, balloonsondes, small UAVs, kites, gliders, and tethered balloons).
Questions - contact Rick Petty (rick.petty@science.doe.gov)
References:
1. Stephens, G., “Cloud Feedbacks in the Climate System: A Critical Review,” Journal of Climate, 18(2): 237-273, January 2005. (ISSN: 1520-0442) (Abstract available at: http://adsabs.harvard.edu/abs/2005JCli...18..237S )
2. Evans, K. F., “In-Situ Cloud Sensing with Multiple Scattering Lidar: Simulations and Demonstration,” Journal of Atmospheric and Oceanic Technology, 20: 1505-1522, 2003. (ISSN: 0739-0572) (Abstract available at: http://climate.gsfc.nasa.gov/viewPaperAbstract.php?id=725)
3. Eatough, D. J., et al., “A Multiple-System Multi-Channel Diffusion Denuder Sampler for the Determination of Fine-Particulate Organic Material in the Atmosphere,” Atmospheric Environment, Part A: General Topics, 27A(8): 1213-1219, June 1993. (ISSN: 0004-6981)
4. Ellingson, R. G., et al., “The Intercomparison of Radiation Codes Used in Climate Models--Long Wave Results,” Journal of Geophysical Research, 96: 8929-8953, May 20, 1991. (ISSN: 0148-0227)
5. Global Change Subcommittee of the Biological and Environmental Research Advisory Committee (BERAC), A Reconfigured Atmospheric Science Program, Technical Report, pp. 18-21, U.S. DOE Office of Biological and Environmental Research, April 2004. (Full text available at: http://www.er.doe.gov/production/ober/berac/ASP.pdf)
6. Gogou, A. I., et al., “Determination of Organic Molecular Markers in Marine Aerosols and Sediments: One Step Flash Chromatography Compound Class Fractionation and Capillary Gas Chromatographic Analysis,” Journal of Chromatography, 799(1-2): 215-231, March 13, 1998. (ISSN: 0021-9673)
7. Grosjean, D., et al., “Evolved Gas Analysis of Secondary Organic Aerosols,” Aerosol Science and Technology, 21(4): 306-324, 1994. (ISSN: 0278-6826)
8. Hansen, A. D., et al., “The Aethalometer–An Instrument for the Real-Time Measurement of Optical Absorption by Aerosol Particles,” paper presented at the International Conference on Carbonaceous Particles in the Atmosphere, Linz, Austria, September 11, 1983, Berkeley, CA: Lawrence Berkeley Laboratory, August 1983. (DOE Report No. LBL-16106) (NTIS Order No. DE84000400.) Abstract and ordering information available from National Technical Information Service (NTIS). Telephone: 1-800-553-6847. Website: http://www.ntis.gov/. (Search by order no. Please note: Items that are unavailable via the Website might be obtained by phoning NTIS.)
9. Platt, C. M., “Lidar and Radiometric Observations of Cirrus Clouds,” Journal of Atmospheric Sciences, 30: 1191–1204, 1973. (ISSN: 0022-4928)
10. Spinhirne, J. D., et al., “Vertical Distribution of Aerosol Extinction Cross Section and Inference of Aerosol Imaginary Index in the Troposphere by Lidar Technique,” Journal of Applied Meteorology, 19: 426-438, 1980. (ISSN: 8944-8763)
11. Klett, J. D., “Lidar Inversion with Variable Backscatter/Extinction Ratios,” Applied Optics, 24: 1638–1643, 1985. (ISSN: 0003-6935)
12. Platt, C. M., “Remote Sounding of High Clouds: Optical Properties of Midlatitude and Tropical Cirrus,” Journal of Atmospheric Sciences, 44: 729-747, 1987. (ISSN: 0022-4928)
13. Sassen, K., et al., “Optical Scattering and Microphysical Properties of Subvisual Cirrus Clouds, and Climatic Implications,” Journal of Applied Meteorology, 28: 91-98, 1989. (ISSN: 8944-8763)
14. Ansmann, A., et al., “Independent Measurement of Extinction and Backscatter Profiles in Cirrus Clouds by Using a Combined Raman Elastic-Backscatter Lidar,” Applied Optics, 33: 7113–7131, 1992. (ISSN: 0003-6935)
15. Goldsmith, J. E., et al., “Turn-Key Raman Lidar for Profiling Atmospheric Water Vapor, Clouds, and Aerosols,” Applied Optics, 37: 4979-4990, 1998. (ISSN: 0003-6935)
16. Eloranta, E. W., “A Practical Model for the Calculation of Multiply-Scattered Lidar Returns,” Applied Optics, 37: 2464–2472, 1998. (ISSN: 0003-6935)
17. Wiscombe, W. J. and Grams, G. W., “Backscattered Fraction in Two-Stream Approximations,” Journal of Atmospheric Sciences, 33: 2440-2451, 1976. (ISSN: 0022-4928)
18. Kahnert, M., and Kylling, A., “Radiance and Flux Simulations for Mineral Dust Aerosols: Assessing the Error Due to Using Spherical or Spheroidal Model Particles,” Journal of Geophysical Research-Atmospheres, 109(D9), 2004. (ISSN: 0148-0227D)
19. Anderson, T. L., et al., “Performance Characteristics of a High-Sensitivity, Three-Wavelength Total Scatter/Backscatter Nephelometer,” Journal of Atmospheric and Oceanic Technology, 13: 967-986, 1996. (ISSN: 1520-0426) (Abstract and ordering information available at: http://ams.allenpress.com/amsonline/?request=get-toc&issn=1520-0426&volume=13&issue=5)
20. Porter, J., et al., “Aerosol Phase Function and Size Distributions from Polar Nephelometer Measurements During the SEAS Experiment,” 12th Conference on Interactions of the Sea and Atmosphere, American Meteorological Society, Long Beach, CA, February 9-13, 2003. (Conference Presentation 9.13) (Short summary available at: http://ams.confex.com/ams/annual2003/12ISA/index.html. Scroll down to Session 9: Red SEAS Experiments, 2:00 pm.)
21. Whiteman, D. N., et al., “Raman Lidar System for the Measurement of Water Vapor and Aerosols in the Earth's Atmosphere,” Applied Optics, 31: 3068-3082, 1992. (ISSN: 0003-6935)
22. Stephens, G. L., et al., “The Department of Energy’s Atmospheric Radiation Measurement (ARM) Unmanned Aerospace Vehicle (UAV) Program,” Bulletin of the American Meteorological Society, 81(12): 2915-2937, 2000. (ISSN: 0003-0007)
23. Global Change Working Group of the Biological and Environmental Research Advisory Committee, Review of the U. S. Department of Energy’s Atmospheric Radiation Measurement’s Unmanned Aerospace Vehicle (ARM UAV) Program, December 2002. (Full text available at: http://www.science.doe.gov/ober/berac/UAVreport.pdf)
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