Mid‐latitude stratospheric aerosol layer enhancement by El Chichon: The first year

Abstract

Measurements are reported in this paper which indicate the nature of the enhancement of the stratospheric aerosol layer by month for the first full year following the Spring 1982 eruptions of El Chichon. The aerosol optical depths as a function of wavelength are obtained by differencing mean monthly values obtained before and after the eruptions. The first enhancement above background was detected in September 1982. The inverted size distributions indicate a steady increase to larger mean size particles each month with a radius near 0.6 micrometers during the last reported month of March 1983. This size is considerably larger than that which is generally assumed for the sulfuric acid aerosols which form following an eruption.

Atmospheric Turbidity and Aerosol Size Distribution in Winter at Tsukuba: Effects of the Eruption of E1 Chichon

“…Our relatively monodispersive size distributions for stratospheric aerosols agree well with the size distribution obtained by Michalsky et al (1984) for their JAN/FEB observations at 46.4*N. On the other hand, size distributions of stratospheric aerosols were measured on board the NASA U-2 aircraft using particle size spectrometers by Knollenberg and Huffman (1983), and using palladium wire impactors by Oberbeck et al (1983) over the North America continent.…”

“…This and the comparison in Fig. 5(a) suggest that *a(*) in our December model seem to be a little overestimated ; but we believe that the stratospheric optical thickness at that time over Tsukuba was not so small as the values estimated by Michalsky et al (1984) and Dutton and Deluisi (1984) (See the next section).…”

“…In the figure stratospheric optical thicknesses estimated from solar extinction measurements by photometers are compared. The values by Michalsky et al (1984) were estimated by the similar method to the present study from ground-based measurements.…”

Aerosol Monitoring Using a Scanning Spectral Radiometer in Sendai, Japan

“…The results in Fig. 8 show that aerosols of El Chichon origin had monomodal volume spectra with a mode radius of about 0.5 ,*m. These volume spectra are in good agreement with those observed around northern hemisphere mid-latitudes retrieved from groundbased solar irradiance measurements (Michalsky et al, 1984;Asano et al, 1985) and from direct and indirect airborne measurements (Knollenberg and M. Shiobara, T. Hayasaka, T. Nakajima and M. Tanaka Huffman,1983; Oberbeck et al, 1983;Hofmann and Rosen, 1984;Spinhirne and King, 1985;Nakajima et al, 1986a). Airborne samples of aerosols in the stratosphere and their component analysis with scanning electron microscopy and energy dispersive X-ray spectroscopy were carried out by several investigators after the eruption of El Chichon (e.g.…”

“…In the present study, size distributions of stratospheric aerosols due to the El Chichon eruption were estimated as a difference between columnar size distributions before and after the eruption. After investigating the results and referring to previous studies on El Chichon aerosols (Knollenberg and Huffman,1983;Oberbeck et al, 1983;Hofmann and Rosen, 1984;Michalsky et al, 1984;Asano et al, 1985;Spinhirne and King, 1985;Nakajima et al, 1986a), we constructed a model of stratospheric aerosols pertaining to the period after the El Chichon eruption. Size distributions of tropospheric aerosols (including the background stratospheric aerosols in the strict sense) were also derived by subtracting the modeled distribution of the El Chichon aerosols from the columnar total aerosol distributions.…”