HR: 15:45h
AN: A54A-02    [Abstracts]
TI: Solar Ultraviolet Spectral Irradiance Data for Atmospheric Studies
AU: * DeLand, M T
EM: matthew_deland@ssaihq.com
AF: Science Systems and Applications, Inc. (SSAI), 10210 Greenbelt Rd. Suite 400, Lanham, MD 20706 United States
AU: Cebula, R P
EM: richard_cebula@ssaihq.com
AF: Science Systems and Applications, Inc. (SSAI), 10210 Greenbelt Rd. Suite 400, Lanham, MD 20706 United States
AB: Spectral solar ultraviolet (UV) measurements began in late 1978 with Nimbus-7 SBUV, and have continued to the present using overlapping data sets from multiple instruments (SBUV/2 on NOAA satellites, UARS SUSIM and SOLSTICE). Solar irradiance in the middle and near ultraviolet wavelength region (200-400 nm) represents only 8% of the Sun's irradiance output, but has a profound effect on the Earth's stratosphere. Variations in mid-UV irradiance over a solar cycle constitute approximately 30% of the total observed solar energy variation. Solar mid-UV irradiance is deposited in the atmosphere at 30-50 km, so understanding the spectral and temporal dependence of these variations is critical to characterizing the long-term energy input to the stratosphere. The typical magnitude of irradiance variations over an 11-year solar cycle is 6-8% at 200 nm, 3-4% at 250 nm, and less than our current detection capabilities (1-2%) longward of 300 nm. Characterization of time-dependent solar UV variations for stratospheric data analysis or modeling has often been done using proxy indexes such as the 10.7 cm flux. While this index reproduces the general shape of solar variations on decadal timescales, it does not fully capture short-term variations that can be equal in magnitude to the solar cycle changes. The Mg II proxy index is more accurate for this purpose because it has a better physical connection to the mid-UV solar irradiance. We are developing a composite spectral irradiance data set that will provide a complete representation of solar UV forcing for analysis of long-term stratospheric changes during the period 1978-2004, and will continue into the future with measurements from the SORCE mission.
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0342 Middle atmosphere--energy deposition
DE: 1650 Solar variability
DE: 7536 Solar activity cycle (2162)
DE: 7549 Ultraviolet emissions
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly