Trends in the nonvolcanic component of stratospheric aerosol over the period 1971–2004

Abstract

[1] The six longest records of stratospheric aerosol (in situ measurements at Laramie, Wyoming, lidar records at: Garmisch-Partenkirchen, Germany; Hampton, Virginia; Mauna Loa, Hawaii; São José dos Campos, Brazil, and SAGE II measurements) were investigated for trend by (1) comparing measurements in the 3 volcanically quiescent periods since 1970 using standard analysis of variance techniques, and (2) analyzing residuals from a time/volcano dependent empirical model applied to entire data sets. A standard squared-error residual minimization technique was used to estimate optimum parameters for each measurement set, allowing for first order autocorrelation, which increases standard errors of trends but does not change magnitude. Analysis of variance over the 3 volcanically quiescent periods is controlled by the end points (pre-El Chichón and post-Pinatubo), and indicates either no change (Garmisch, Hampton, São José dos Campos, Laramie-0.15 mm) or a slight, statistically insignificant, decrease (Mauna Loa, Laramie-0.25 mm), À1 ± 0.5% yr À1 . The empirical model was applied to the same records plus 1020 nm SAGE II data separated into 33 latitude/altitude bins. No trend in stratospheric aerosol was apparent for 31 of 33 SAGE II data sets, 3 of 4 lidar records, and in situ measurements at 0.15 mm. For Hampton and Laramie-0.25 mm, the results suggest a weak negative trend, À2 ± 0.5% yr À1, while 2 SAGE II data sets (30-35 km, 30°and 40°N) suggest a positive trend of similar magnitude. Overall we conclude that no long-term change in background stratospheric aerosol has occurred over the period 1970-2004.

35 yr of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

“…Since 1972, time series have been obtainable from lidar measurements, balloon ascents (Hofmann et al, 1975), and also satellite observations (McCormick et al, 1981;Thomason et al, 1987). For recent reviews see Deshler et al (2006) and Deshler (2008). These observations, covering a number of important eruptions, have led to clear evidence of the mainly volcanic nature of the stratospheric aerosol.…”

“…A scientific summary for the period 1976-1999 was given by Jäger (2005). Deshler et al (2006) and Deshler (2008) compared the results with those from the most important stations performing stratospheric aerosol sounding.…”

“…The lidar system at IMK-IFU is an instrument of both NDACC and EARLINET. This system was originally built in 1973 (Impulsphysik GmbH), based on a ruby laser, and, in addition to a large number of routine and campaign-type tropospheric measurements (e.g., Reiter and Carnuth, 1975 Jäger et al, 1988Jäger et al, , 2006Forster et al, 2001;Trickl et al, 2003Trickl et al, , 2011, has been almost continually used for measurements of stratospheric aerosol since autumn 1976 (e.g., Jäger, 2005;Deshler et al, 2006;Fromm et al, 2008bFromm et al, , 2010. The lidar was converted to a spatially scanning system with a Nd:YAG laser (Quanta Ray, GCR 4, 10 Hz repetition rate, about 700 mJ per pulse at 532 nm) in the early 1990s for additional investigation of contrails (Freudenthaler, 2000;Freudenthaler et al, 1994Freudenthaler et al, , 1995.…”

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

“…These measurements will be used (in this study) as prior knowledge, with the help of which SAGE II spectral extinction measurements will be evaluated to obtain new estimates of aerosol properties under non-volcanic conditions. The balloone-borne measurements from Laramie along with ground based lidar measurements at two mid-latitude sites (Osborn et al, 1995;Jäger, 2005) and two tropical sites (Barnes and Hofmann, 1997;Simonich and Clemesha, 1997) provide the longest stratospheric aerosol records available (Deshler et al, 2006). They are particularly valuable, for instance, for having captured the complete cycle of three major volcanic eruptions (Fuego, 1974, 14 • N;El Chichón, 1982, 17 • N;Pinatubo, 1991, 15 • N) which have not been measured in as much detail or even not at all by satellite instruments.…”

The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling

“…In situ balloon observations continue to be used and have provided highly valuable data sets, including most notably the long time series of optical particle counter measurements from Laramie, WY (Deshler et al, 2003(Deshler et al, , 2006Kovilakam and Deshler, 2015). Aircraft-borne nephelometers (Beuttell and Brewer, 1949;Charlson et al, 1969) acquire detailed in situ measurements, providing, for example, plume composition (Murphy et al, 2014), but are spatially limited to the aircraft track.…”