HR: 15:30h
AN: A43D-08    [Abstracts]
TI: Trends in Non-Volcanic Stratospheric Aerosol Determined from 20 years of SAGE II Measurements
AU: * Deshler, T
EM: deshler@uwyo.edu
AF: Department of Atmospheric Science, Dept. 3038 1000 E. University Avenue, Laramie, WY 82071 United States
AU: Anderson-Sprecher, R
EM: Sprecher@uwyo.edu
AF: Department of Statistics, Dept. 3332 1000 E. University Ave., Laramie, WY 82071 United States
AU: Liu, P S
EM: peterliu@uwyo.edu
AF: Department of Atmospheric Science, Dept. 3038 1000 E. University Avenue, Laramie, WY 82071 United States
AU: Eidhammer, T
EM: trude@uwyo.edu
AF: Department of Atmospheric Science, Dept. 3038 1000 E. University Avenue, Laramie, WY 82071 United States
AU: Yongxiao, J
EM: jianyx@uwyo.edu
AF: Department of Atmospheric Science, Dept. 3038 1000 E. University Avenue, Laramie, WY 82071 United States
AB: Junge's initial stratospheric aerosol measurements (1959-1960), at the end of a long volcanically quiescent period, and the long term stratospheric aerosol measurements beginning in the 1970s have been the basis for investigations of the trend of non-volcanic stratospheric aerosol. These investigations have been hampered by the difficulty of determining periods free of volcanic perturbations. Since 1959 there have been approximately 30 eruptions with volcanic explosivity indices of 4 or more. The longest records of stratospheric aerosol measurements, extending over 30 years, capture the three major aerosol-producing eruptions, Fuego, El Chichon and Pinatubo. The 20 year SAGE II record captures the decay of El Chichon aerosol, interrupted by the smaller tropical eruptions of Nevado del Ruiz, Nyamuragira, and Kelut, and the complete Pinatubo aerosol cycle. SAGE II measurements have not, in the past, been used to investigate trends since the data are limited by providing only two inter-volcanic periods between major eruptions, and only one cycle for a large eruption, Pinatubo. To circumvent this problem, and use the complete SAGE II record, we have developed a parametric exponential decay model to "devolcanize" the aerosol signal. The aerosol signal from the 5 major volcanic influences over the SAGE II record are each characterized by a 4 parameter model. The volcanic influence on the SAGE II measurements, captured by this 20 parameter model, is then subtracted from the 20 year record. The residual autocorrelated signal is then statistically investigated for trends. The modeling and trend investigation is done in 10 degree latitude bins (50N to 50S) and three altitude intervals (18-23, 24-29, 30-34 km). The results, which will be presented at the meeting, suggest that the global SAGE II data supplement nicely similar investigations of the four lidar, and one in situ, 30-year records of stratospheric aerosol. This work is being completed as part of the SPARC assessment of stratospheric aerosol.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0370 Volcanic effects (8409)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting