Thirty years of in situ stratospheric aerosol size distribution measurements from Laramie, Wyoming (41°N), using balloon‐borne instruments

Abstract

[1] Vertical profiles of size-resolved aerosol concentrations above Laramie, Wyoming (41°N), have been measured for the past thirty years, . During this period, two somewhat different optical particle counters have been used to measure particles with radii !0.15 mm, whereas the instrument to measure condensation nuclei (CN) has not changed significantly since the late 1970s. The two optical particle counters measure aerosols !0.15, 0.25 mm and aerosols !0.15-2.0 mm in twelve size classes. These measurements have concentration (N) uncertainties / ±N À0.5 , but with a minimum of ±10%. Sizing uncertainties are about ±10%. The impact of these uncertainties on size distribution fitting parameters and aerosol moments are approximately ±30% and ±40%. The long-term record from these measurements indicates that volcanoes have controlled stratospheric aerosol abundance for 20 of the past 30 years. The present period, beginning in 1997, represents the longest volcanically quiescent period in the record. These and other measurements clearly show that stratospheric aerosol are now in a background state, a state rarely occurring in recent times, and that this background state is not significantly different than observations in 1979. Aerosol volumes and surface areas, inferred from size distributions fit to the measurements, are compared with SAGE II satellite estimates of surface area and volume. For volume the measurements are in agreement within measurement error throughout the record. For surface area there is good agreement for a volcanic aerosol laden stratosphere, but for background aerosol conditions the SAGE II estimates are about 40% less than the in situ measurements. Present aerosol surface areas are $1.0 (0.6) mm 2 cm À3 in the 15-20 (20-25) km layer based on in situ measurements. The Laramie size distribution record is now available to the community over the internet. (8409); KEYWORDS: stratospheric aerosol size distributions, volcanic stratospheric aerosol, background stratospheric aerosol, in situ aerosol size distribution measurements, optical particle counters, balloonborne aerosol measurements Citation: Deshler, T., M. E. Hervig, D. J. Hofmann, J. M. Rosen, and J. B. Liley, Thirty years of in situ stratospheric aerosol size distribution measurements from Laramie, Wyoming (41°N), using balloon-borne instruments,

Composition and evolution of volcanic aerosol from eruptions of Kasatochi, Sarychev and Eyjafjallajökull in 2008–2010 based on CARIBIC observations

“…The diameter of the sulphate aerosol estimated by Martinsson et al (2005) was obtained from the effective radius of stratospheric aerosol from lidar observations (Bauman et al, 2003) during a period with low volcanic activity. Thus the radius is underestimated for volcanic aerosol which usually exhibit larger diameters (Bauman et al, 2003;Deshler et al, 2003). Ash particles usually have substantially larger diameters (Schumann et al, 2011).…”

Balloon-borne stratospheric BrO measurements: comparison with Envisat/SCIAMACHY BrO limb profiles

“…Aerosol loadings are taken from Deshler et al (2003) as recommended by Dufour et al (2005). Photolysis rates are Furthermore, each BrO observation conducted by the remote sensing instruments SCIAMACHY, SAOZ and DOAS is a composite of changing photochemical conditions (due to changing SZA) along the line-of-sight.…”

A High-Sensitivity Low-Cost Optical Particle Counter Design

“…Small weather balloons are excellent platforms for temperature, ozone, and water vapor profile measurements. However, only a few particle sensors suitable for balloon deployment have been described in the literature (Hofmann et al 1975;Hayashi et al 1998;Sugita et al 1999;Deshler et al 2003;Kasai et al 2003;Iwasaki et al 2007;Hill et al 2008). Most of these sensors are not capable of measuring particles below 150-nm diameter and/or are not suitable for disposable sondes.…”