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Accuracy Assessments and Validation of an Expanded UV Irradiance Database from Satellite Total Ozone Mapping Spectrometer (TOMS)The TOMS UV irradiance database (1978 to 2000) has been expanded to include 5 new products (noon irradiance at 305, 310, 324, and 380 nm, and noon erythemal-weighted irradiance), in addition to the existing erythemal daily exposure, which permit direct Comparisons with ground-based measurements from UV spectrometers. Sensitivity studies are conducted to estimate uncertainties of the new TOMS UV irradiance data due to algorithm apriori assumptions. Comparisons with Brewer spectrometers as well as filter radiometers are used to review of the sources of known errors. Inability to distinguish between snow and cloud cover using only TOMS data results in large errors in estimating surface UV using snow climatology. A correction is suggested for the case when the regional snow albedo is known from an independent source. The summer-time positive bias between TOMS UV estimations and Brewer measurements can be seen at all wavelengths. This suggests the difference is not related to ozone absorption effects. We emphasize that uncertainty of boundary layer UV aerosol absorption properties remains a major source of error in modeling UV irradiance in clear sky conditions. Neglecting aerosol absorption by the present TOMS algorithm results in a positive summertime bias in clear-sky UV estimations over many locations. Due to high aerosol variability the bias is strongly site dependent. Data from UV-shadow-band radiometer and well-calibrated CIMEL sun-sky radiometer are used to quantify the bias at NASA/GSFC site in Greenbelt, MD. Recommendations are given to enable potential users to better account for local conditions by combining standard TOMS UV data with ancillary ground measurements.
Document ID
20040081274
Document Type
Conference Paper
Authors
Krotkov, N. A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Herman, J. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Fioletov, V. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Seftor, C. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Larko, D. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Vasilkov, A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Subject Category
Meteorology and Climatology
Meeting Information
International Quadrennial Ozone Symposium (QOS 2004)(Kos)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.