A global climatology of stratospheric aerosol size distribution parameters derived from SAGE II data over the period 1984–2000: 2. Reference data

Abstract

[1] In a companion paper, a global climatology was presented for different parameters characterizing the size distribution of stratospheric aerosols; the particle number density, median radius, and mode width of the particle size distribution were assumed to be lognormal. Those aerosol parameters were retrieved by optical inversion of Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction profiles. The data cover the time period 1984-2000. In this second part of the study, we present the climatology in a more quantitative way, and starting from the case of the Mount Pinatubo eruption in June 1991, we try to derive reference data for the three considered aerosol parameters. Using four time intervals representative of the different phases of the aerosol relaxation after a major eruption, we investigate the data set spanning the period June 1991 to mid-1999 and present a spatiotemporal description of the aerosol distribution for the whole relaxation period. The range of the data dispersion due to seasonal effects and random variations is also estimated. Finally, a study of the error on the three parameters is presented for the whole data set, as well as an overview of our validation efforts.

Optimal estimation retrieval of aerosol microphysical properties from SAGE~II satellite observations in the volcanically unperturbed lower stratosphere

“…For the number size distribution parameters there are less values to compare and larger differences between the data sets. In number density, the uncertainties reported by Bingen et al (2004b) are larger than the OE error estimates, whereas those estimated by Wang et al (1989) are considerably smaller. The 11% reported by Wang et al (1989), however, account only for particles greater than 0.15 µm although the great majority of the retrieved OE sizes are smaller than that (Fig.…”

“…8). Similarly, uncertainties in median particle radius estimated by Wang et al (1989) are smaller than those reported by Bingen et al (2004b) and smaller than those achieved through Optimal Estimation, but their error estimates apply only to radii between 0.1 and 0.7 µm. However, although particles smaller than 0.1 µm may contribute little to the total aerosol extinction, their contribution is important to get accurate estimates of the retrieved aerosol properties (Sect.…”

“…For instance, at an altitude of 17.5km at mid-latitude (40 to 70 • N/S) in 1999, the retrieved radii range between 0.25 and 0.33 µm (NH) or 0.27 and 0.37 µm (SH), whereas the OE results are on the order of 0.08 µm. Simultaneously, the number densities retrieved by Bingen et al (2004b), which they found to be low compared to coincident in situ Optical Particle Counter measurements (Bingen et al, 2004b), are smaller than the OE number densities. Bingen Table 7.…”

“…The total errors are expected to be higher by about 50% due to disregarded systematic (method bias) errors and contributions from particles smaller than 0.1 µm. The methods and the conditions under which these uncertainties were achieved are described in: (1) Wurl (2008), (2) Steele et al (1999), (3) Thomason and Poole (1993), (4) Steele and Turco (1997), (5) Anderson et al (2000), (6) Bingen et al (2004b), (7) Wang et al (1989), and (8) Bauman et al (2003a) et al ascribe their low number densities and overestimated particle sizes to the inability of SAGE II optical measurements to discriminate very thin particles in the Rayleigh limit of scattering. This suggests that the larger OE number densities and smaller OE median radii tend to be more realistic than those presented by Bingen et al (2004b).…”

Development, Production and Evaluation of Aerosol Climate Data Records from European Satellite Observations (Aerosol_cci)

“…For stratospheric aerosols, time series of extinction at 1 µm were developed from satellite measurements back to 1978 [5,14]. More than 16 years of stratospheric particle size distribution parameters have been developed from the SAGE II (Stratospheric Aerosol and Gas Experiment) experiment [15][16][17].…”