A new approach to retrieval of aerosol size distributions and integral properties from SAGE II aerosol extinction spectra

Abstract

Abstract. A new approach to the retrieval of aerosol size distributions and integral properties from Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction spectra is proposed. This method assumes that the aerosol size distribution can be approximated by a histogram of number density as a function of particle size. The retrieved number density in each bin is expressed as a linear combination of the SAGE II aerosol extinctions at four or fewer wavelengths. The coefficients in the weighted linear combination are obtained by minimizing the retrieval error averaged for a set of testing size distributions. The same method has been applied to retrieve aerosol surface area and volume densities from SAGE II aerosol extinctions. The retrieval accuracy was studied by calculating the aerosol surface area and volume densities for six aerosol size distributions retrieved by using the proposed linear minimizing error method. In general, the retrieval error increases with the decreasing number of wavelength-dependent extinction measurements available for retrieval. Besides accuracy, the proposed method has the advantage of not requiring an initial guess or a weighting function. Furthermore, it is very simple and fast. Another advantage is that the proposed method can still be applied to the case when the number of reliable aerosol extinction is less than four. The formulas presented in this paper can be used easily by investigators to retrieve surface area and volume densities from SAGE II aerosol extinction spectra at different altitudes for a variety of purposes. The proposed new method can also be extended to retrieve properties from other remote sensing systems. The application of the proposed method for instrument design is discussed.

SAGE II measurements of stratospheric aerosol properties at non-volcanic levels

“…This will be demonstrated later in this section. Many techniques have been applied to this calculation for SAGE II data, each of which filled this "blind spot" in a somewhat different manner (Wang et al, 1989;Thomason et al, 1997;Steele et al, 1997;Yue et al, 1999;Bingen et al, 2004). The operational SAD retrieval puts relatively little material at radii smaller than 50 nm and thus is likely to produce SAD values that are biased low to some degree (Thomason et al, 1997).…”

Post‐Mount Pinatubo eruption ground‐based infrared stratospheric column measurements of HNO3, NO, and NO2 and their comparison with model calculations

“…Sulfate aerosol surface area density [ Yue , 1999] from version 6.1 SAGE II data was used through the end of 1999. Missing data points from early in the post‐Pinatubo period were filled with surface area density calculated by the AER 2‐D sulfate aerosol model [ Weisenstein et al , 1997] and later in the period from Chipperfield and Randel [2003] values.…”

“…Daily average stratospheric columns of HNO 3 , NO, and NO 2 are reported taking into account the vertical sensitivity of the measurements based on averaging kernels. These results are compared with two‐dimensional chemistry‐transport model calculations based on version 6.1 Stratospheric Aerosol and Gas Experiment (SAGE) II monthly average aerosol surface area densities through 1999 [ Yue , 1999] with all boundary conditions specified by the “ab baseline” trend scenario for World Meteorological Organization ( WMO ) [2003], including the trends of N 2 O, CH 4 , chlorofluorocarbons, chlorine, and bromine species as a function of time. The SAGE II time series has been extended through the end of the analysis period by repeating the 1999 values.…”

Anti‐Correlation between stratospheric aerosol extinction and the Ångström parameter from multiple wavelength measurements with SAGE II—A characteristic of the decay period following major volcanic eruptions

“…3(a) and (c) Comparisons of the Angstr6m parameter with the effective radii obtained by the method of Yue [1999] and derived from simple Mie-calculations proved that the AngstrSm parameter is an effective indicator of particle size. More extensive analysis, including microphysical considerations, would shed light on the particle formation processes and the mechanism of their loss from the stratosphere.…”