About the Rhythms of Variability of the Submicron Aerosol Characteristics in the Near-Ground Air Layer in West Siberia (original) (raw)
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Aerosol Absorption and Scattering Measurements: Field Measuremnets and Laboratory Characterizations
2011
Determining the overall impact of atmospheric aerosols on radiative balance requires knowledge of the relative amounts of scattering and absorbing aerosols, their distributions, and their chemical and optical properties. This proposal was a continuation of measurements of aerosol scattering and absorption begun in Mexico City in 2003 in collaboration with MCMA 2003 and continuing in the Atmospheric Science Program field study, Megacity Aerosol Experiment-Mexico City, (MAX-Mex) during March of 2006 aimed at determining the variability of aerosol optical properties. A suite of instrumentation was deployed in MAX-Mex at site TO, located in the northern part of the Mexico City Metropolitan Area, (MCMA), for the characterization of the aerosol optical properties in the field. Measurements were made of the following aerosol properties: (1) aerosol absorption as a function of wavelength, measured at two minute intervals with a 7-wavelength Aethalometer (2) aerosol scattering as a function of wavelength, measured at one minute intervals with a 3-wavelength nephelometer; 3) aerosol scattering as a function of relative humidity (RH), measured at one minute intervals with 2 single-wavelength nephelometers operated under dry (10% RH) and wet (80% RH) conditions; and 4) collection of sizefractionated aerosol samples on quartz fiber filters at 12 hour intervals (day/night) for further laboratory characterization. Aerosol filter samples were also collected at site Tl (located north of MCMA) for comparison with those collected in the city center. Preliminary results from in situ measurements have indicated an enhanced UV absorption in the afternoon over that expected from black carbon (BC) aerosols alone. These results are directly applicable to both modeling of aerosol radiative forcing and satellite optical depth retrieval algorithms. Both of these applications assume that the aerosol absorption is due only to BC with a wavelength dependence of A, " whereas results obtained in MAX-Mex show that the aerosol wavelength exponent varies over Mexico City from-0.7 to-1.5.
Atmospheric Measurement Techniques Discussions, 2015
The primary objective of the Complex Aerosol Experiment was measurement of microphysical, chemical, and optical properties of aerosol particles in the surface air layer and free atmosphere. The measurement data were used to retrieve the whole set of aerosol optical parameters, necessary for radiation calculations. Three measurement cycles were performed within the Experiment during 2013: in spring, when the aerosol generation is maximal; in summer (July), when atmospheric boundary layer altitude and, hence, mixing layer altitude are maximal; and in late summer – early autumn, during the period of nucleation of secondary particles. Numerical calculations were compared with measurements of downward solar fluxes on the Earth's surface, performed in the clear-sky atmosphere in summer periods in 2010–2012 in a background region of the boreal zone of Siberia. It has been shown that, taking into account the instrumental errors and errors of atmospheric parameters, the relative differen...
Journal of Geophysical Research, 1994
Ground-based measurements of the solar transmission and sky radiance in a horizontal plane through the Sun are taken in several geographical regions and aerosol types: dust in a desert transition zone in Israel, sulfate particles in Eastern and Western Europe, tropical aerosol in Brazil, and mixed continental/maritime aerosol in California. Stratospheric aerosol was introduced after the eruption of Mount Pinatubo in June 1991. Therefore measurements taken before the eruption are used to analyze the properties of tropospheric aerosol; measurements from 1992 are also used to detect the particle size and concentration of stratospheric aerosol. The measurements are used to retrieve the size distribution and the scattering phase function at large scattering angles of the undisturbed aerosol particles. The retrieved properties represent an average on the entire atmospheric column. A comparison between the retrieved phase function for a scattering angle of 120 ø, with phase function predicted from the retrieved size distribution, is used to test the assumption of particle homogeneity and sphericity in radiative transfer models (Mie theory). The effect was found to be small (20% _ 15%). For the stratospheric aerosol (sulfates), as expected, the phase function was very well predicted using the Mie theory. A model with a power law size distribution, based on the spectral dependence of the optical thickness, a, cannot estimate accurately the phase function (up to 50% error for A = 0.87/am). Before the Pinatubo eruption the ratio between the volumes of sulfate and coarse particles was very well correlated with a. The Pinatubo stratospheric aerosol destroyed this correlation. The aerosol optical properties are compared with analysis of the size, shape, and composition of the individual particles by electron microscopy of in situ samples. The measured volume size distributions before the injection of stratospheric aerosol consistently show two modes, sulfate particles with r m • 0.2 /am and coarse particles with r m • 0.7 /am. The "window" in the tropospheric aerosol in this radius range was used to observe a stable stratospheric aerosol in 1992, with r m • 0.5 /am. A combination of such optical thickness and sky measurements can be used to assess the direct forcing and the climatic impact of aerosol. Systematic inversion for the key aerosol types (sulfates, smoke, dust, and maritime aerosol) of the size distribution and phase function can give the relationship between the aerosol physical and optical properties that can be used to compute the radiative forcing. This forcing can be validated in dedicated field experiments. Paper number 94JD00229. 0148-0227/94/94 JD-00229505.00 remote sensing procedures of aerosol particles from satellite sensors [Fraser et al., 1984; Tanr• et al., 1988a; Kaufman et al., 1990; King et al., 1992; Holben et al., 1992; Dulac et al., 1992]. Tropospheric aerosol particles have a short lifetime (about a week), and as a result their properties vary from one region to another and vary with time. Aerosol concentration and properties depend on the strengths of the sources, on atmospheric processes that affect them, and on transport of the particles from one region to another [Holben et al., 1991]. Because of variability in aerosol properties it is difficult to assess aerosol climatology, since measurements in remote locations, such as taken for CO2 or CH4, cannot be used to represent the aerosol properties. For a full assessment of aerosol characteristics such measurements have to be performed frequently in locations with different aerosol types and in varying meteorological conditions. Sky brightness and color are determined by scattering and absorption by aerosol particles (solid or liquid particles suspended in the air) and by the atmospheric gases. Mol•c-10,341 10,342 KAUFMAN ET AL.: SIZE DISTRIBUTION AND PHASE FUNCTION OF AEROSOL ular scattering is virtually constant in time. As a result, measurements of the spectral brightness of the sky, in spectral bands where gaseous absorption is minimal, can be used to retrieve information about particle size distribution and optical characteristics [Weinman et al., 1975; Box and Deepak, 1981; Yamamoto and Tanaka, 1969; King et al., 1978; Twitty et al., 1976; Shaw, 1979; Nakajima et al., 1983, 1986a, b; Tanr• et al., 1988b; $hiobara et al., 1991]. The characteristics of aerosol particles, retrieved from groundbased measurements, are representative of their properties averaged over the whole atmospheric column. Analysis of the sky brightness, like other remote sensing techniques, retrieves information on the natural undisturbed particles, while in situ measurements subject the particles to changes in the relative humidity between the ambient air and the environment of the instrument. The collection efficiency of the instrument may be a function of the particle size and, therefore, not representing all the particles equally [Huebert et al., 1990]. Sky measurements, used to retrieve the aerosol characteristics are usually taken in the solar almucantar, a horizontal plane passing through the Sun (the view zenith angle is equal to the solar zenith angle). The main properties of the aerosol particles that are important for climate studies as manifested in recent publications and for remote sensing are (1) size distribution of the KAUFMAN
Atmospheric Measurement Techniques, 2015
The primary objective of this complex aerosol experiment was the measurement of microphysical, chemical, and optical properties of aerosol particles in the surface air layer and free atmosphere. The measurement data were used to retrieve the whole set of aerosol optical parameters, necessary for radiation calculations. Three measurement cycles were performed within the experiment during 2013: in spring, when the aerosol generation is maximal; in summer (July), when atmospheric boundary layer altitude and, hence, mixing layer altitude are maximal; and in late summer/early autumn, during the period of nucleation of secondary particles. Thus, independently obtained data on the optical, meteorological, and microphysical parameters of the atmosphere allow intercalibration and inter-complement of the data and thereby provide for qualitatively new information which explains the physical nature of the processes that form the vertical structure of the aerosol field.
A review of atmospheric aerosol measurements
Atmospheric Environment, 2000
Recent developments in atmospheric aerosol measurements are reviewed. The topics included complement those covered in the recent review by Chow (JAWMA 45: 320}382, 1995) which focuses on regulatory compliance measurements and "lter measurements of particulate composition. This review focuses on measurements of aerosol integral properties (total number concentration, CCN concentration, optical coe$cients, etc.), aerosol physical chemical properties (density, refractive index, equilibrium water content, etc.), measurements of aerosol size distributions, and measurements of size-resolved aerosol composition. Such measurements play an essential role in studies of secondary aerosol formation by atmospheric chemical transformations and enable one to quantify the contributions of various species to e!ects including light scattering/absorption, health e!ects, dry deposition, etc. Aerosol measurement evolved from an art to a science in the 1970s following the development of instrumentation to generate monodisperse calibration aerosols of known size, composition, and concentration. While such calibration tools permit precise assessments of instrument responses to known laboratory-generated aerosols, unquanti"able uncertainties remain even when carefully calibrated instruments are used for atmospheric measurements. This is because instrument responses typically depend on aerosol properties including composition, shape, density, etc., which, for atmospheric aerosols, may vary from particle-to-particle and are often unknown. More e!ort needs to be made to quantify measurement accuracies that can be achieved for realistic atmospheric sampling scenarios. The measurement of organic species in atmospheric particles requires substantial development. Atmospheric aerosols typically include hundreds of organic compounds, and only a small fraction (&10%) of these can be identi"ed by state-of-the-art analytical methodologies. Even the measurement of the total particulate organic carbon mass concentration is beset by di$culties including the unknown extent of evaporative losses during sampling, adsorption of gas-phase organic compounds onto sampling substrates, and the unknown relationship between carbon mass and mass of the particulate organics. The development of improved methodologies for such measurements should be a high priority for the future. Mass spectrometers that measure the composition of individual particles have recently been developed. It is not clear that these instruments will provide quantitative information on species mass concentrations, and more work is needed to routinely interpret the vast quantities of data generated during "eld sampling. Nevertheless, these instruments substantially expand the range of atmospheric aerosol issues that can be explored experimentally. These instruments represent the most signi"cant advance in aerosol instrumentation in recent years.
Aerosol Science and Technology, 2000
Predictions are reported of the size response of various light-scattering aerosol counters manufactured by Particle Measuring Systems. Models considered are those that exploit the high intensity of light available within the cavity of a HeNe gas laser (generically referred to by the manufacturer as "active scattering aerosol spectrometer probes"). The new response function properly averages over particle trajectories through nodes, antinodes, and intermediate regions of the intracavity laser beam. Our studies address probes having two basic scattering geometries: those that collect light scattered over a relatively narrow solid angle (subtending angles between 4° and 22° from the laser beam axis) and those that collect light over a rather large solid angle (between 35° and 120°). The new response function predicts smoother dependence on particle size than the previous response function of Pinnick and Auvermann (1979, J. Aerosol Sei. 10: 55-74) and is in better agreement with measurement. Response calculations for common atmospheric aerosol (water, sulfuric acid, ammonium sulfate, and black carbon) reveal the considerable sensitivity of the response to particle dielectric properties. Comparison of response calculations with the manufacturer's calibration reveals conditions for which the manufacturer's calibration is most appropriate, and the potential for errors (as much as a factor of two in sizing) when it is blindly applied. These results should help the user of these instruments to more realistically interpret size distribution measurements.
Applied Optics, 1978
Recent field measurements of scattered 3.8-pm laser radiation from naturally occurring aerosols were made during a 4-week period in coastal Southern California. Simultaneously, aerosol distribution measurements were made, which, in conjunction with Mie scattering theory, gave estimates of the volume scattering coefficient at the various angles. A comparison shows that (a) calculated volume scattering coefficients generally decrease more rapidly in angle than measurements indicate; (b) on the average, the calculation gives volume backscattering coefficients that are a factor of 2 larger than measured but underpredicts forward scattering by 33%. A second unrelated observation of interest is that volume scattering coefficients in the visible showed 65% correlation with 3.8-gum backscatter (1770) coefficients. meters and relative humidities varying from 30% (-8 Torr H 2 0) to over 80% (14 Torr H 2 0) with the average humidity centered around 50% (see ). On several occasions, a hot dry wind (the Santa Ana condition) blew from the upper California desertland elevating temperatures to 30° (with 50% or less relative humidity). During these days, numerous brush fires were also observed in the vicinity, but on only one occasion were measurements made with smoke haze in the beam path.