Stratospheric aerosol measurements

The first passive remote sensing experiment to measure successfully the abundance of atmospheric aerosols from space was the Stratospheric Aerosol Measurement (SAM II) aboard Nimbus 7 (McCormick et al. 1979). This experiment was a single channel radiometer observing in solar occultation and was the forerunner of SAGE. Stratospheric aerosols have also been measured by their infrared absorptions (e.g. HALOE). 

High latitude aerosol observations have been secured by the Stratospheric Aerosol Measurement (SAM II) satellite system these have shown that the aerosol extinction profiles measured within the northern polar vortex differ significantly above 18 km from those measured outside the vortex (Me Cormick et d., 1983). 

Stratospheric Aerosol Measurements Using the CCD-Based Spectrometer... 

Toon OB, Turco RP, Whitten R, et al. 1981. Implications of stratospheric aerosol measurements for models of aerosol formation and evolution. Geophysical Research Letters 8 23-25. 

LIDAR measurements of stratospheric aerosols (Browell et al., 1990) show that above the frost point, PSCs can be solids, perhaps solid SAT. Pure SAT, which does not form PSCs very efficiently, does not melt until quite high temperatures, about 210-215 K (Middlebrook et al., 1993 Iraci et al., 1995). However,... 

Measurements of the solubility of HBr in sulfuric acid at 220 K gave Henry s law constants from 8.5 X 103 M atm-1 for 72 wt% H2S04 to 1.5 X 107 M atm-1 for 54 wt% H2S04 (Williams et al., 1995 Abbatt, 1995). Application of these values to stratospheric aerosol particles typical of midlatitude conditions gives very small equilibrium concentrations of dissolved HBr i.e., most of the HBr will remain in the gas phase. 

Santer, R M. Herman, D. Tanre, and J. Lenoble, Characterization of Stratospheric Aerosol from Polarization Measurements, J. Geophys. Res., 93, 14209-14221 (1988). 

Zawodny, J. M., and M. P. McCormick, Stratospheric Aerosol and Gas Experiment II Measurements of the Quasi-Biennial Oscillations in Ozone and Nitrogen Dioxide, J. Geophys. Res., 96, 9371-9377 (1991). 

At Arosa, Switzerland, where there are records back to 1926 (the longest data record available), the trend in annual mean 03 has been determined to be —(2.3 + 0.6)% per decade. When contributions due to the solar cycle, temperature, and stratospheric aerosol concentrations are taken into account, the trend is —(1.9 0.6)% per decade. However, the total measured column 03 includes both stratospheric and a smaller tropospheric contribution, and the latter has been increasing (see Chapters 14 and 16). This would tend to mask part of a decrease in stratospheric 03. Applying an estimate of the increase in tropospheric ozone gives a trend in stratospheric 03 of - (3.0 + 0.6)% per decade at Arosa (Staehelin et al., 1998b). 

Cunnold, D. M H. Wang, W. P. Chu, and L. Froidevaux, Comparisons between Stratospheric Aerosol and Gas Experiment II and Microwave Limb Sounder Ozone Measurements and Aliasing of SAGE II Ozone Trends in the Lower Stratosphere, J. Geophys. Res., 101, 10061-10075 (1996). 

Grams, G. W., 1981. In-situ measurements of scattering phase functions of stratospheric aerosol particles in Alaska during July 1979, Geophys. Res. Lett., 8, 13-14. 

The atmospheric concentration of natural and bomb-produced radionuclides has been measured at ground level for several years at three locations throughout the world. The manner in which the concentration decreased suggested a half-residence time for stratospheric aerosols of 11.8 months at 46°N latitude. The annual spring concentration maximum occurred one to four months earlier at 71°N than at 46°N. Cosmogenic 7Be attained a maximum concentration before the bomb-produced radionuclides at 71° N and later than the bomb-produced isotopes at 46°N. The rate of increase toward the annual peak concentration for most radionuclides could be approximated by an exponential in which the concentration doubled every 60 days likewise, the rate of decrease from the maximum concentration could be approximated by an exponential with a half-time of about 40 days for most radionuclides except 7Be at 46°N, which shows a half-time of about 60 days. 

Abstract. A multi-wavelength, multi-sensor Look-Up-Table (LUT) algorithm has been developed to retrieve information about stratospheric aerosols from satellite-based observations of particulate extinction. Specifically, the LUT algorithm combines extinction measurements from SAGE n with similar measurements from the CLAES instrument, and uses the composite spectra in month-latitude-altitude bins to retrieve values and uncertainties of particle effective radius, surface area, volume and size distribution width. 

Figure 1. Stratospheric aerosol effective radii derived from a variety of measurements and techniques [1].

As noted above, the LUT algorithm assumes a unimodal lognormal functional form to describe stratospheric aerosols. This approximation is well suited for most non-volcanic stratospheric aerosols as shown by Pueschel et al. [7] and Yue et al. [8]. Volcanic size distributions, however, are typically bi- or trimodal. This raises the question of whether the assumption of unimodality in the LUT can introduce bias into retrieved values of Rt//, S and V. Russell et al. [1] have shown that retrieved unimodal distributions accurately describe the second, larger mode of several measured bimodal size distributions, but fail to account for the smaller particles in the first mode. The smaller particles, which contribute little to the measured extinction spectra, are not accounted for in the LUT retrievals. Unless this bias is accounted for, the values of Rtff retrieved under the assumption of a unimodal distribution will be overestimated. 

IwASAKA Y., Hayashida S., and Ono A., Increased backscattered light from the stratospheric aerosol layer after Mt. El Chichon eruption laser radar measurements at Nagoya (35 N, 137 E). Geophys. Res. Lett. , 10, 440-442 (1983). 

Our understanding of stratospheric aerosols is still far from being satisfactory. In particular, the gas-to-particle conversion processes involving SO2 oxidation and condensation nuclei formation are still poorly understood. Future research, therefore, should include in situ measurements of aerosols, trace gases and condensation nuclei involved in aerosol formation. Accompanying laboratory studies of relevant chemical processes are also needed. 

Figure 8 Oxidation of SO2 to SO4 in the Pinatubo stratospheric cloud. The total SO2 mass curve indicates the loss of SO2 by oxidation to sulfate aerosol according to an initial loading of 17 Tg of SO2 (after Read et at. (1993), and 3 Tg lower than the TOMS-only estimate of Bluth et al. (1992)) and a 33 d e-folding time. The circles indicate satellite measurements of stratospheric SO2 burden from Read et al. (1993). The total aerosol mass curve is obtained by modeling the aerosol mass generated by sulfate oxidation and an e-folding time for aerosol loss of 1 yr. The squares show estimates of the stratospheric aerosol mass from Baran et al. (1993). Daily rates of SO2 conversion and aerosol production are shown by the two other curves (labeled).

Zasetsky, A.Y., J.J. Sloan, R. Escribano and D. Fernandez A new method for the quantitative identification of the composition, size and density of stratospheric aerosols from high resolution IR satellite measurements, Geophys. Res. Lett. 29,2071 (2002) doi 10.1029/2002GL015816. 

In Central Asia, the measurements of vertical profiles of concentration and the optical characteristics of stratospheric and tropospheric aerosol have been conducted since 1988 at the Lidar Station Teplokluchenka (Kyrgyz Republic), with the use of a laser-location method. The high mountain Lidar Station Teplokluchenka (LST) is located over 2000 m above sea level, southeast of a high mountain lake Issyk-Kul in Central Tien-Shan (42.5° N, 78.4" E). It is a xmique scientific station for complex monitoring of tropospheric and stratospheric aerosol by lidar in the center of the Asian part of the global geoecological system. LST was established in 1987. 

Table I, provided yet another instrumental approach for balloon experiments intended to measure the extinction of solar radiation by stratospheric aerosol. Spectrometer 4, Table I, based on the use of a pyroelectric vidicon image device, was developed to measure the strong absorption bands of non-isonuclear molecules ( 2-5 ym range). Recently we have developed spectrometer 5, Table I, based on the use of a self-scanned solid state pyroelectric array sensor. The main advantages of this sensor, over the pyroelectric vidicon, are its improved sensitivity and reduced channel-to-channel cross-talk.

Aneja VP, Overton JH Jr, Cupitt LT, et al. 1980. Measurements of emission rates of carbon disulfide from biogenic sources and its possible importance to the stratospheric aerosol layer. Chemical Engineering Communication 4 721-727. 

Since its discovery the existence of the stratospheric aerosol layer has been proved by many investigators (e.g. Mossop, 1965 Friend, 1966 Kondratyev et ai, 1969). A mathematical model of the particles in the aerosol layer, constructed by Friend (1966), led to a size distribution with a maximum in the vicinity of 0.3 fim particle radius. However, according to the results of more recent measurements by Bigg (1976) the actual distribution has its maximum at smaller sizes. The observations of Kondratiev et al. (1974) show that the stratospheric concentration of aerosol particles with radii larger than 0.2 /an may be as great as 1 cm-3. However, this concentration is strongly time dependent (Bigg, 1976) as we shall discuss in Subsection 4.4.3. 

About ten years later a new stratospheric aerosol program was performed. In this case, particles were collected between 17 and 28 km by absolute filters having a collection efficiency of virtually 100 % in all size ranges. Table 25 gives the results of a sampling day when particles were collected at an altitude of 18 km. It the last column of the table the percentage of sulfate ions possibly neutralized by NH4 is also presented. It can be seen that the concentrations measured by this more recent... 

The first stratospheric aerosol chemical analyses showed that only a small quantity of the aerosol particles in the lower stratosphere could be of meteoritic origin (e.g. no nickel was found in the samples, see Table 24). This problem was studied in detail by Shedlovsky and Paisly (1966) who found by means of neutron activation of aerosol particles collected on filters that the stratospheric Fe/Na ratio is close to that reported for the Earth s crust. They concluded that less than 10 % of the iron and sodium identified at altitudes of 19-21 km come from meteorites. However, it is possible that between 30 and 50 km, where no such measurements were made, the meteoritic fraction of the aerosol is much more significant. 

Global climatologies of stratospheric aerosols have been produced from observations by satellite instruments. Hitchman et al. (1994), for example, have provided meridional distributions of measured extinction ratios based on 9 years of data from the Stratospheric Aerosol and Gas Experiment (SAGE I and II) and the Stratospheric Aerosol... 

Thomason, L.W., L.R. Poole, and T. Deshler, A global climatology of stratospheric aerosol surface area density deduced from Stratospheric Aerosol and Gas Experiment II measurements 1984-1994. J Geophys Res 102, 8967, 1997. 

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