Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: S. G. Jennings x
  • Refine by Access: All Content x
Clear All Modify Search
P. F. Nolan and S. G. Jennings

Abstract

Measurements have been made of both extinction coefficients in an evaporating laboratory cloud at wavelength λ = 10.591 μm using a CO2 laser, and of liquid water content (LWC) at the center of the cloud using a continuous filtration LWC device. Cloud uniformity has been promoted and monitored within the laboratory chamber. The measurements give an overall linear relation between extinction and liquid water content independent of droplet-size distribution in reasonably good agreement with the Chýlek prediction. The measurements show significantly better agreement with the Chýlek prediction for the narrower cloud drop-size distributions. The broader size distribution data show an underestimate in extinction compared to the Chýlek prediction, providing the first experimental evidence for the large radius limit (radius ≤ 12 μm) in use of the Chýlek relation.

Full access
R. G. Pinnick, S. G. Jennings, and G. Fernandez

Abstract

Volatile properties of aerosols at an isolated rural site in south-central New Mexico were measured with a light-scattering particle counter equipped with a temperature-controlled heated inlet. Intermittent measurements throughout a one-year period show that submicron particles am highly volatile and display temperature-fractionation characteristics of ammonium sulfate or bisulfate. It is estimated that 60–98% of the submicron aerosol fraction (by mass) is composed of these sulfates. Larger supermicron particles with radii r > 0.4 μm, which are composed mostly of quartz and clay minerals of soil origin, are relatively involatile.

Full access
R. G. Pinnick, S. G. Jennings, Petr Chýlek, and H. J. Auvermann

Abstract

A linear relationship, independent of the form of the size-distribution, between extinction at wave-lengths around λ = 11 µm, absorption around λ = 3.8 and 9.5 µm, and liquid water content of atmospheric fogs has been verified using 341 droplet size distribution measurements made under a variety of meteorological conditions. The results suggest that integrated liquid water content along a path in fog can be determined from measurement of CO2 laser (λ = 10.6 µm) transmission along the path, and that liquid water content at a particular point in fog can be inferred from in situ measurement of fog-droplet absorption with a deuterium fluoride laser (λ = 3.8 µm) or a suitably tuned C02 laser (λ = 9.5 µm) spectrophone.

Full access
R. G. Pinnick, D. L. Hoihjelle, G. Fernandez, E. B. Stenmark, J. D. Lindberg, G. B. Hoidale, and S. G. Jennings

Abstract

Vertical structure of the size distribution and number concentration of particulates in atmospheric fog and haze near Grafenwöhr, West Germany, were measured with a balloonborne light-scattering aerosol counter for periods spanning parts of eight days in February 1976. For haze (∼5 km visibility) conditions, little vertical variation is seen; but for low visibility (<1 km) fog conditions, significant vertical increases in concentration of droplets with radii larger than 4 μm are seen over the first 150 m altitude. For haze, the particle size distribution is approximated by a log-normal with geometric mean radius rg≈0.2 μm and geometric standard deviation σg≈1.9. For fog, a bimodal distribution is found with a relative maximum for the larger particle mode at radii of 4 to 6 μm and corresponding values rg≈5 μm and σg≈1.6; the smaller particle mode has values of rg≈0.3 μm to rg≈0.6 μm and σg≈1.8 to σg≈2.5. Liquid water content values for haze and fog range from 10−4 to 0.45 g m−3. Extinction calculated from the particle size distributions shows an approximate 1/λ wavelength dependence for haze conditions, but nearly neutral (wavelength independent) extinction for heavy fog. A correlation exists between calculated particulate extinction and calculated liquid water content, independent of particle size distribution, for the fogs and hues studied.

Full access
Bruce A. Wielicki, D. F. Young, M. G. Mlynczak, K. J. Thome, S. Leroy, J. Corliss, J. G. Anderson, C. O. Ao, R. Bantges, F. Best, K. Bowman, H. Brindley, J. J. Butler, W. Collins, J. A. Dykema, D. R. Doelling, D. R. Feldman, N. Fox, X. Huang, R. Holz, Y. Huang, Z. Jin, D. Jennings, D. G. Johnson, K. Jucks, S. Kato, D. B. Kirk-Davidoff, R. Knuteson, G. Kopp, D. P. Kratz, X. Liu, C. Lukashin, A. J. Mannucci, N. Phojanamongkolkij, P. Pilewskie, V. Ramaswamy, H. Revercomb, J. Rice, Y. Roberts, C. M. Roithmayr, F. Rose, S. Sandford, E. L. Shirley, Sr. W. L. Smith, B. Soden, P. W. Speth, W. Sun, P. C. Taylor, D. Tobin, and X. Xiong

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5–50 μm), the spectrum of solar radiation reflected by the Earth and its atmosphere (320–2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a “NIST [National Institute of Standards and Technology] in orbit.” CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

Full access