Measured and calculated optical property profiles in the mixed layer and free troposphere

Rosen, James M.; Bodhaine, Barry A.; Boatman, Joe F.; Deluisi, John; Post, Madison J.; Kim, Young; Schnell, R. C.; Sheridan, Patrick J.; Garvey, Dennis M.

doi:10.1029/92jd01355

Cited by 17 publications

(6 citation statements)

References 20 publications

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“…This value can be compared with the backscattersonde results through application of an appropriate optical model. Using an ensemble of tropospheric size distributions that are known to reproduce measured aerosol optical properties [Rosen et al, 1992], the converted satellite extinction value gives an ABSR of 0.18 at 940 nm, which is reasonably close to the actually observed values of 0.15 to 0.3 (Figure 1) and strongly suggests that the same background aerosol is being observed by both sensors.…”

Section: Correlationssupporting

confidence: 73%

“…Similar calculations using the bimodal tropospheric size distributions reported by Hofmann [1993] and Pueschel et al [1994] give a CI of 5.0 +_ .5 for tropospheric aerosols with effective radii (reff) in the range 0.07 to 0.25/xm (average equal to 0.12) where reff is the area weighted particle radius defined by Hansen and Travis [1974]. Using the free tropospheric size distributions reported by Rosen et al [1992], a range in CI from about 7 to 12 corresponds to r•ff ranging from about 0.25 to 2.0/xm, respectively.…”

Section: Introductionmentioning

confidence: 64%

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Tropospheric aerosol backscatter at a midlatitude site in the northern and southern hemispheres

Rosen¹,

Kjome²,

Liley³

1997

J. Geophys. Res.

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Abstract. Monthly balloon borne aerosol backscatter measurements at --•173 ø and wavelengths of 940 and 490 nm have been made at Lauder, New Zealand (45øS), and Laramie, Wyoming (41øN), since 1992. The presentation and analysis here focus on the tropospheric results which suggest that a similar quasi steady state background aerosol appears over both sites with superimposed seasonal disturbances that are probably related to arid region dust storms and biomass burning. Volcanic influences on the free troposphere are found to be minimal. In contrast to the background aerosol, the aerosol disturbances show a strong hemispheric difference with fewer perturbations over Lauder as well as significantly differing vertical profile structure, as might be expected at a remote site. Our interpretation of the higher resolution backscatter measurements substantially supports the conclusions drawn from the lower resolution stratospheric aerosol and gas experiment (SAGE) and stratospheric aerosol measurement (SAM) satellite observations. IntroductionThe number of systematic, long term measurement programs focused on global aerosols of the free troposphere is remarkably small, especially when compared to the number of studies of aerosols of the stratosphere and in the near-surface boundary layer. Nevertheless, important progress has been made in revealing the nature of free tropospheric aerosols since the late 1980s, when a review assessment of the state of knowledge indicated a disturbing lack of information [Heintzenberg, 1989]. Because no single observational program has been able to address all aspects of free tropospheric aerosols, a unified description must be assembled and verified utilizing a variety of complementary, as well as directly comparable, measurements. A number of intriguing questions still remain, which to date have no satisfactory or generally accepted answers. MethodologyIn this work we employ two data sets originally obtained for the study of stratospheric aerosols, but which are also highly appropriate for aerosol investigations throughout the entire troposphere. The quasi-monthly measurements were made at Laramie, Wyoming (41øN), and Lauder, New Zealand (45øS), using balloon borne dual wavelength backscatter sensors (backscattersondes) which concurrently also provide ozone concentration, temperature, and relative humidity [Rosen and Kjome, 1991]. Since most of the soundings consistently take place after sunset in relatively calm conditions, with minimal cloud cover, the observations cannot be considered strictly random, and it is possible that a systematic bias has been introduced into the data set. However, this is a problem common to essentially all tropospheric aerosol studies and probably does not lead to significant misconceptions.Copyright 1997 by the American Geophysical Union. Paper number 97JD01486.0148-0227/97/97 JD-01486509.00The earliest soundings began in 1988 over Laramie but were not conducted on a regular basis until June 1990. The Lauder soundings began in March 1992. As of this writing, ...

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Section: Correlationssupporting

confidence: 73%

Section: Introductionmentioning

confidence: 64%

Tropospheric aerosol backscatter at a midlatitude site in the northern and southern hemispheres

Rosen¹,

Kjome²,

Liley³

1997

J. Geophys. Res.

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“…The RMS deviation of calculated from measured values is 16%. Reported aerosol optical depth uncertainties obtained from similar studies range from 12% to 31% [ Rosen et al , 1992; Hartley et al , 2000; Kato et al , 2000]. The uncertainty range of LACE 98 aerosol optical depth data is of comparable magnitude.…”

Section: Resultsmentioning

confidence: 93%

Vertical variability of aerosol properties observed at a continental site during the Lindenberg Aerosol Characterization Experiment (LACE 98)

et al. 2002

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[1] In the summer of 1998, an aerosol column closure experiment was conducted over eastern Germany as part of the Lindenberg Aerosol Characterization Experiment (LACE 98). The experimental platforms involved were two aircraft equipped with aerosol in situ instrumentation, an airborne aerosol backscatter lidar and solar irradiance sensors (upwelling and downwelling) to measure optical and microphysical aerosol properties relevant for radiative forcing in the entire atmospheric column from the boundary layer to the tropopause region. Using Mie theory and reasonable assumptions on the particle complex refractive index, the hemispheric backscatter fraction and spectral light scattering coefficients were calculated from the measured aerosol size distribution data. A comparison between optical parameters derived from particle size distribution measurements and optical properties measured by independent techniques yields an uncertainty range of ±30% for the calculated aerosol optical parameters. Detailed information on the vertical variability of the particle size distribution, the aerosol extinction coefficient and the hemispheric backscatter fraction is given, which is applicable for a realistic representation of aerosol properties in climate models. The estimated daily averaged aerosol shortwave radiative forcing varies from À33 ± 12 to À12 ± 5 W m À2 , and respective aerosol optical depths at l = 0.710 mm range from 0.18 to 0.06.

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“…Examples in the marine environment include NARE-96 (Cowling et al, 1998), ACE-1 (Bates et al, 1998), ACE-2 (Collins et al, 2000a;, and INDOEX (de Reuss et al, 2001). Over coastal and continental locations, following earlier work of Rosen et al (1992), Kim et al (1993a), Gunter et al (1993), Pinnick et al (1993) and Gunter (1994), more elaborate airborne data sets have been acquired in the Arctic (Hegg et al, 1996), in the US mid-Atlantic coastal region (Hegg et al, 1997;Hartley et al, 2000), and over the Los Angeles Basin (Collins et al, 2000b), among others.…”

Section: Introductionmentioning

confidence: 99%

Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

Han

Montague

Snider

2003

Atmospheric Environment

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Particle size distributions, and scattering and absorption coefficients were measured over the Green River basin of Wyoming during the Southwest Wyoming Visibility Study (SWYVIS) in February and March 1996. Eleven flights were carried out, using the Wyoming King Air research aircraft. In the least polluted regions of the planetary boundary layer, particle number densities detected in the diameter range 0.13-3.0 mm were o100 cm À3 . Aloft, in the stable air of the free troposphere, they were generally even lower, often falling to a few tens of particles per cm 3 . Analyses of bulk aerosol filter samples showed that organic carbonaceous material was the dominant chemical component, with sulfate and refractory species being the largest inorganic components. Combining the filter data with separately measured black carbon mass loading values allowed refractive indices for the aerosol to be calculated, so that PCASP measured size distributions could be revised. Characterizing size parameters were obtained by fitting particle populations to bimodal lognormal distributions. Particle size distributions were somewhat broader at higher altitudes so that larger particles made greater contributions to extinction. Optical closure was attempted by comparing scattering and total extinctions computed by Mie theory with the corresponding values derived from the observations. While the calculated and measured single scattering albedo average values were in reasonably good agreement, even though individual pairs of values sometimes differed significantly, computed scattering coefficients often exceeded those derived from the measurements, by an average of 60%. Reasons for this discrepancy are explored, including the possible modification of the size distribution by partial or total volatilization of particles within the nephelometer and its inlet. r

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Measured and calculated optical property profiles in the mixed layer and free troposphere

Cited by 17 publications

References 20 publications

Tropospheric aerosol backscatter at a midlatitude site in the northern and southern hemispheres

Tropospheric aerosol backscatter at a midlatitude site in the northern and southern hemispheres

Vertical variability of aerosol properties observed at a continental site during the Lindenberg Aerosol Characterization Experiment (LACE 98)

Airborne measurements of aerosol extinction in the lower and middle troposphere over Wyoming, USA

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