HR: 0830h
AN: A21D-0997    [PDF]
TI: TOMS and Ground-based Measurements: Long-term Trends, Spatial Variability, Cloud Effects, and Data Quality.
AU: * Eide, H A
EM: heide@stevens-tech.edu
AF: Stevens Institute of Technology, Department of Physics and Engineering Physics, Castle Point on Hudson, Hoboken, NJ 07030 United States
AU: Dahlback, A
EM: arne.dahlback@fys.uio.no
AF: University of Oslo, Department of Physics, Blindern, Oslo, N0316 Norway
AU: Stamnes, K
EM: kstamnes@stevens-tech.edu
AF: Stevens Institute of Technology, Department of Physics and Engineering Physics, Castle Point on Hudson, Hoboken, NJ 07030 United States
AU: H{\o}yskar, B
EM: britt@nilu.no
AF: Norwegian Institute for Air Research (NILU), Kjeller, Oslo, N2007 Norway
AU: Olsen, R
EM: olsen@osb1.wff.nasa.gov
AF: NASA GSFC, Wallops Flight Facility, Wallops Island, VA 23337 United States
AU: Schmidlin, F
EM: fjs@osb1.wff.nasa.gov
AF: NASA GSFC, Wallops Flight Facility, Wallops Island, VA 23337 United States
AU: Tsay, S
EM: tsay@climate.gsfc.nasa.gov
AF: NASA GSFC, Climate and Radiation Branch, Greenbelt, MD 20771 United States
AB: Ground-based measurements and TOMS measurements are mutually beneficial to each other. Ground-based measurements of UV radiation and total column ozone amounts are important for the validation of TOMS measurements. For example, it has been shown that TOMS measurements has a tendency to under-estimate ground UV exposure. Some of these effects can perhaps be ascribed to local cloud effects or choice of ozone profiles in the retrieval algorithm. More ground-based measurements are needed to establish the cause of these discrepancies. Recent technology advances have made ground-based measurements of UV doses and ozone column amounts with inexpensive multi-channel filter instruments not only possible, but also an attractive alternative to other more labor-intensive and weather dependent methods. Filter instruments can operate unattended for long periods of time, and it is possible to obtain accurate ozone column amounts even on cloudy days. We present results from extensive comparisons of the performance of several ground-based instruments (the NILU-UV and GUV filter instruments, as well as the Dobson and Brewer instruments) against the EP-TOMS instrument. The data used in the comparisons are from three different sites where we have had the opportunity to operate more than one type of UV instruments for extended periods of time. The sites include the University of Oslo, Norway, the NASA Goddard Space Flight Center facilities at Wallops Island, VA, and Greenbelt, MD and the University of Alaska, Fairbanks (during the TOMS3F campaign). Our results show that ozone column amounts obtained with current filter-type instruments are just as good as those obtained with the Dobson instrument, and might even out-perform the Dobson instrument on cloudy days. The TOMS measurements are shown to exhibit some more variability, but there is on average very good agreement with the ground- based measurements even for high solar zenith angles (SZA). Further more, our comparison shows that ozone column amounts are very insensitive to the choice of ozone profile for SZA $<$ 65$^\circ$. We also show how the TOMS measurements can be used to detect drift in ground-based filter instruments over time.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0360 Transmission and scattering of radiation
DE: 0394 Instruments and techniques
DE: 3360 Remote sensing
DE: 3394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting