Search Results

You are looking at 1 - 10 of 10 items for

  • Author or Editor: Philip B. Russell x
  • All content x
Clear All Modify Search
Philip B. Russell and Patrick Hamill

Abstract

Recent experimental results indicate that little or no solid ammonium sulfate is present in background stratospheric aerosols. Other results allow straightforward calculation of sulfuric acid/water droplet properties (acidity, specific gravity, refractive index) as functions of stratosphere temperature and humidity. We combine these results with a variety of latitudinal and seasonal temperature and humidity profiles to obtain corresponding profiles of droplet properties. These profiles are used to update a previous model of stratospheric aerosol refractive index. The new model retains the simplifying approximation of vertically constant refractive index in the inner stratosphere, but has sulfuric acid/water refractive index values that significantly exceed the previously used room temperature values. Mean conversion ratios (e.g., extinction-to-number, backscatter-to-volume) obtained using Mie scattering calculations with the new refractive indices are very similar to those obtained for the old indices, because the effect of deleting ammonium sulfate and increasing acid indices tend to cancel each other.

Full access
Philip B. Russell and Glenn E. Shaw

Abstract

By analysing two sets of atmospheric solar measurements, Laulainen and Taylor conclude that conventional Volz sunphotometry is subject to considerable error arising from apparent day-to-day variation in J 0, the zero-airmass instrument response (“meter deflection”). They determined J 0 from the atmospheric data by using a curve-fitting and extrapolation procedure which is very similar to the familiar graphical “Langley plot” method. However, this method is subject to large errors under conditions of time-varying or horizontally inhomogeneous turbidity. We present an example of such errors and reinspect their data. This indicates that the apparent variation in J 0 was probably in large part (if not completely) due to changing turbidity conditions, rather than an actual change in instrument calibration. Thus their data do not necessarily support their conclusion that “much existing Volz turbidity data are of dubious value.” We emphasize that indiscriminate day-to-day determination of J 0 by curve fitting is risky at best, and recommend the use of artificial calibration sources of known radiance as the most conclusive method to determine the response of a photometer.

Full access
Philip B. Russell and Gerald W. Grams

Abstract

Several analytical models of the radiative effects of aerosol layers on global climate provide the common result that the critical value (ρc) of the ratio (ρ) of aerosol layer absorption to hemispheric backscattering is given by
ρcA2A
where A is taken to be the albedo of the earth's surface, or of the present earth–atmosphere system. The models predict that introduction of a new aerosol layer with ρ > ρ c will cause a decrease in system albedo, and a layer with ρ < ρ c will cause an increase. In this paper we demonstrate this common result for &rho c and then employ recently published data on the complex refractive index and size distribution of atmospheric surface layer soil particles to compute values of ρ. The resulting values (5 < ρ < 28) are quite large compared to previous estimates. Together with the above model result they indicate that increased generation of such airborne soil particles will tend to increase the input of solar energy to the earth–atmosphere system. This “heating” effect results, in part, from the relatively large mean particle sizes used in the computations. The effects of particle asphericity on the computed ρ values are discussed.
Full access
Philip B. Russell and Edward E. Uthe

A network of 13 sodars (acoustic radars) was operated in the San Francisco Bay Area for 2.5 months of the 1976 smog season. The goal was to produce a data base on time-dependent mixing depth and stability patterns for input to air quality models.

The large set (~1000 site-days) of sodar facsimile records was filmed to provide a more compact, convenient, and accessible data product. A manual digitization scheme was devised and used to convert the continuous sodar data to hourly values describing mixing depth and a near-surface stability indicator. These values can easily be input to computerized air quality models and can readily be understood by a user with no sodar experience.

Numerous sodar-inferred mixing depths were compared to those inferred from 1) simultaneous measurements of temperature and humidity profiles and 2) lidar-measured haze and cloud layering. These and previous tests show good overall agreement, demonstrating that in the San Francisco Bay Area, sodar measurements compare very favorably with alternate techniques for determining mixing depth. This result derives in part from the Bay Area's special meteorology (frequent strong, low, elevated inversions) and should not be extended indiscriminately to other areas.

Several time-dependent maps of mixing depth illustrate the use of the data. The maps show changing patterns of mixing layer development caused by surface heating and cooling and varying marine influence. The patterns can vary markedly from day to day.

Full access
Philip B. Russell and Richard D. Hake Jr.

Abstract

Fifteen lidar observations of the stratosphere aerosol were made between February and November 1975. All observations revealed the greatly increased particulate backscattering that followed the eruption of the volcano Fuego in October 1974. Vertical structure consisted initially of multiple layers, which later merged to form a single, broader peak. Nearly all of the increased scattering was confined to altitudes below 20 km. Hence, aerosol layer centroids in 1975 were typically several kilometers below their altitude prior to the eruption.

Our observations began in mid-February, at about the time of maximum northern midlatitude influence of the volcanic injection. From late February on, both vertically integrated particulate back-scattering and the peak ratio of particulate to gaseous backscattering displayed approximately exponential declines, with mean 1/e lifetimes of eight and eleven months, respectively. These relatively short residence times are a combined consequence of the low altitude of the volcanic particles and their larger mean size as compared to the preinjection, or unperturbed, aerosol. The peak scattering ratio of our average 1975 profile was 1.7, and the vertically integrated particulate backscattering was 3.6 × 10−4 sr−1 (both at λ = 694 nm). The mean midvisible particulate optical thickness, derived from measured back-scattering and realistic optical models, was about 0.03, approximately six times the mean value in the year before the Fuego eruption, but not as large as values observed for some years after the 1963 Agung eruption.

Radiative and thermal consequences of the measured post-Fuego layer were computed using several recently published models. The models yield a 1975 mean layer albedo of about 1% or less; they predict a temperature increase of several kelvins at the altitude of the layer, caused by the infrared absorption bands of the sulfuric acid particles. At the surface, the models predict a temperature decrease of considerably less than 1 K, partly because of the small optical thickness of the volcanic layer, and partly because of its short residence time relative to the earth-ocean thermal response time.

Full access
Philip B. Russell and John M. Livingston

Abstract

The slant-path (or zenith-angle scanning) lidar technique is used to measure boundary-layer optical depths for ten different times during a single day. For the range of optical depths encountered (0.03–0.14 at 0.69 μm wavelength), 1σ measurement uncertainties are about 0.03. The major source of uncertainty is daytime skylight background, effects of which are mitigated in this experiment by the low boundary-layer top height (<1.4 km above the lidar).

Resulting particle column backscatter-to-extinction ratios vary between 0.010 and 0.053 sr−1. By assuming that these ratios are independent of height, vertical extinction profiles and the optical depth of a layer below a tower-mounted radiometer pair are derived. This radiometer pair is used to measure the change in surface plus layer albedo caused by the aerosol layer. The consistency of albedo and optical thickness measurements is tested by comparing measured albedo changes to those calculated from the optical thickness measurements. When reasonable values are assumed for particle refractive index and relative size distribution (not measured in this experiment), results agree to within the uncertainty arising from the 0.03 optical thickness measurement uncertainty.

Full access
Robert W. Bergstrom, Philip B. Russell, and Phillip Hignett

Abstract

Measurements are presented of the wavelength dependence of the aerosol absorption coefficient taken during the Tropical Aerosol Radiative Forcing Observational Experiment (TARFOX) over the northern Atlantic. The data show an approximate λ −1 variation between 0.40 and 1.0 μm. The theoretical basis of the wavelength variation of the absorption of solar radiation by elemental carbon [or black carbon (BC)] is explored. For a wavelength independent refractive index the small particle absorption limit simplifies to a λ −1 variation in relatively good agreement with the data. This result implies that the refractive indices of BC were relatively constant in this wavelength region, in agreement with much of the data on refractive indices of BC. However, the result does not indicate the magnitude of the refractive indices.

The implications of the wavelength dependence of BC absorption for the spectral behavior of the aerosol single scattering albedo are discussed. It is shown that the single scattering albedo for a mixture of BC and nonabsorbing material decreases with wavelength in the solar spectrum (i.e., the percentage amount of absorption increases). This decease in the single scattering albedo with wavelength for black carbon mixtures is different from the increase in single scattering albedo for most mineral aerosols (dusts). This indicates that, if generally true, the spectral variation of the single scattering albedo can be used to distinguish aerosol types. It also highlights the importance of measurements of the spectral variation of the aerosol absorption coefficient and single scattering albedo.

Full access
Greg McFarquhar, Beat Schmid, Alexei Korolev, John A. Ogren, Philip B. Russell, Jason Tomlinson, David D. Turner, and Warren Wiscombe

No Abstract available.

Full access
John H. Seinfeld, Gregory R. Carmichael, Richard Arimoto, William C. Conant, Frederick J. Brechtel, Timothy S. Bates, Thomas A. Cahill, Antony D. Clarke, Sarah J. Doherty, Piotr J. Flatau, Barry J. Huebert, Jiyoung Kim, Krzysztof M. Markowicz, Patricia K. Quinn, Lynn M. Russell, Philip B. Russell, Atsushi Shimizu, Yohei Shinozuka, Chul H. Song, Youhua Tang, Itsushi Uno, Andrew M. Vogelmann, Rodney J. Weber, Jung-Hun Woo, and Xiao Y. Zhang

Although continental-scale plumes of Asian dust and pollution reduce the amount of solar radiation reaching the earth's surface and perturb the chemistry of the atmosphere, our ability to quantify these effects has been limited by a lack of critical observations, particularly of layers above the surface. Comprehensive surface, airborne, shipboard, and satellite measurements of Asian aerosol chemical composition, size, optical properties, and radiative impacts were performed during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) study. Measurements within a massive Chinese dust storm at numerous widely spaced sampling locations revealed the highly complex structure of the atmosphere, in which layers of dust, urban pollution, and biomass- burning smoke may be transported long distances as distinct entities or mixed together. The data allow a first-time assessment of the regional climatic and atmospheric chemical effects of a continental-scale mixture of dust and pollution. Our results show that radiative flux reductions during such episodes are sufficient to cause regional climate change.

Full access
M. Ades, R. Adler, Rob Allan, R. P. Allan, J. Anderson, Anthony Argüez, C. Arosio, J. A. Augustine, C. Azorin-Molina, J. Barichivich, J. Barnes, H. E. Beck, Andreas Becker, Nicolas Bellouin, Angela Benedetti, David I. Berry, Stephen Blenkinsop, Olivier. Bock, Michael G. Bosilovich, Olivier. Boucher, S. A. Buehler, Laura. Carrea, Hanne H. Christiansen, F. Chouza, John R. Christy, E.-S. Chung, Melanie Coldewey-Egbers, Gil P. Compo, Owen R. Cooper, Curt Covey, A. Crotwell, Sean M. Davis, Elvira de Eyto, Richard A. M de Jeu, B.V. VanderSat, Curtis L. DeGasperi, Doug Degenstein, Larry Di Girolamo, Martin T. Dokulil, Markus G. Donat, Wouter A. Dorigo, Imke Durre, Geoff S. Dutton, G. Duveiller, James W. Elkins, Vitali E. Fioletov, Johannes Flemming, Michael J. Foster, Richard A. Frey, Stacey M. Frith, Lucien Froidevaux, J. Garforth, S. K. Gupta, Leopold Haimberger, Brad D. Hall, Ian Harris, Andrew K Heidinger, D. L. Hemming, Shu-peng (Ben) Ho, Daan Hubert, Dale F. Hurst, I. Hüser, Antje Inness, K. Isaksen, Viju John, Philip D. Jones, J. W. Kaiser, S. Kelly, S. Khaykin, R. Kidd, Hyungiun Kim, Z. Kipling, B. M. Kraemer, D. P. Kratz, R. S. La Fuente, Xin Lan, Kathleen O. Lantz, T. Leblanc, Bailing Li, Norman G Loeb, Craig S. Long, Diego Loyola, Wlodzimierz Marszelewski, B. Martens, Linda May, Michael Mayer, M. F. McCabe, Tim R. McVicar, Carl A. Mears, W. Paul Menzel, Christopher J. Merchant, Ben R. Miller, Diego G. Miralles, Stephen A. Montzka, Colin Morice, Jens Mühle, R. Myneni, Julien P. Nicolas, Jeannette Noetzli, Tim J. Osborn, T. Park, A. Pasik, Andrew M. Paterson, Mauri S. Pelto, S. Perkins-Kirkpatrick, G. Pétron, C. Phillips, Bernard Pinty, S. Po-Chedley, L. Polvani, W. Preimesberger, M. Pulkkanen, W. J. Randel, Samuel Rémy, L. Ricciardulli, A. D. Richardson, L. Rieger, David A. Robinson, Matthew Rodell, Karen H. Rosenlof, Chris Roth, A. Rozanov, James A. Rusak, O. Rusanovskaya, T. Rutishäuser, Ahira Sánchez-Lugo, P. Sawaengphokhai, T. Scanlon, Verena Schenzinger, S. Geoffey Schladow, R. W Schlegel, Eawag Schmid, Martin, H. B. Selkirk, S. Sharma, Lei Shi, S. V. Shimaraeva, E. A. Silow, Adrian J. Simmons, C. A. Smith, Sharon L Smith, B. J. Soden, Viktoria Sofieva, T. H. Sparks, Paul W. Stackhouse Jr., Wolfgang Steinbrecht, Dimitri A. Streletskiy, G. Taha, Hagen Telg, S. J. Thackeray, M. A. Timofeyev, Kleareti Tourpali, Mari R. Tye, Ronald J. van der A, Robin, VanderSat B.V. van der Schalie, Gerard van der SchrierW. Paul, Guido R. van der Werf, Piet Verburg, Jean-Paul Vernier, Holger Vömel, Russell S. Vose, Ray Wang, Shohei G. Watanabe, Mark Weber, Gesa A. Weyhenmeyer, David Wiese, Anne C. Wilber, Jeanette D. Wild, Takmeng Wong, R. Iestyn Woolway, Xungang Yin, Lin Zhao, Guanguo Zhao, Xinjia Zhou, Jerry R. Ziemke, and Markus Ziese
Full access