HR: 0800h
AN: SA21A-0333    [Abstracts]
TI: Spectral Measurements of PMCs from SBUV/2 Instruments
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: Shettle, E P
EM: shettle@nrl.navy.mil
AF: Naval Research Laboratory, Remote Sensing Division, Code 7227, Washington, DC 20375-5351 United States
AU: Thomas, G E
EM: gary.thomas@lasp.colorado.edu
AF: LASP, University of Colorado, Boulder, CO 80309-0392 United States
AU: Olivero, J J
EM: oliveroj@erau.edu
AF: Dept. of Physical Sciences, Embry-Riddle University, Daytona Beach, FL 32114 United States
AU: Rusch, D W
EM: david.rusch@lasp.colorado.edu
AF: LASP, University of Colorado, Boulder, CO 80309-0392 United States
AB: The SBUV/2 instrument is designed to monitor stratospheric profile and total column ozone using measurements of the Earth's backscattered ultraviolet albedo. We have previously demonstrated that the normal radiance measurements from SBUV/2 instruments, which sample 12 discrete wavelengths between 252-340 nm during each scan, can be used to identify polar mesospheric clouds (PMCs). A 25-year PMC data set has been constructed using data from six SBUV/2 instruments, three of which are currently operating. Some SBUV/2 instruments also periodically view the Earth in continuous scan mode, covering the wavelength range 160-400 nm with 0.15 nm sampling. These data can be analyzed for the presence of PMCs using the same detection algorithm applied to discrete SBUV/2 data. PMC spectra observed by SBUV/2 instruments show a monotonic variation in brightness over the wavelength range 250-295 nm, with maximum enhancements above the background albedo of 10-15% at 250 nm. This result is consistent with microphysical model predictions, using a mean particle radius of 60 nm and a log-normal distribution width of 1.4. We find no evidence for a systematic localized increase in PMC brightness near 260 nm, in contrast to the recently reported results from the MSX UVISI instrument [{\it Carbary et al.}, 2004]. The flat spectral dependence of PMCs in the mid-UV is observed from three different SBUV/2 instruments in both Northern and Southern Hemisphere data over a 13-year span. The spectral signature of the SBUV/2 continuous scan PMC data does not require the existence of a bimodal particle size distribution, as suggested by {\it Carbary et al.} [2004]. Carbary, J. F., D. Morrison, and G. J. Romick (2004), Evidence for bimodal particle distribution from the spectra of polar mesospheric clouds, {\it Geophys. Res. Lett.}, {\it 31}, L13108, doi:10.1029/2004GL020101.
DE: 0320 Cloud physics and chemistry
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting