11th Conference on Atmospheric Radiation and the 11th Conference on Cloud Physics

Friday, 7 June 2002
Estimate Earth Surface Ultraviolet Radiation Exposure from ISCCP-D1 and TOMS Measurements
Pubu Ciren, University of Maryland, College Park, MD; and Z. Li
Poster PDF (1.9 MB)
To better understand the impact of global ozone depletion, satellite remote sensing plays an indispensable role in providing information on the spatial and temporal variations of surface UV radiation. In this study, we developed an approach to derive the climatology of the Earth’s surface daily-integrated UV exposure from a combination of ISCCP-D1 3-hourly reflectance data and TOMS ozone amount data. They are validated against ground-based measurements at 6 stations. A general good agreement between the estimated and measured UV is found for most stations, the relative mean and root mean square (rms) differences vary from –12 to 23% and from 33 to 48% respectively. Among them, owing to the prevailing clear sky condition, San Diego has a fairly low mean difference (9%) and the lowest rms difference (33%). An increasing trend of the rms difference with cloud amount implies that mismatch between satellite and ground-based measurements is a major influential factor. The effect of the diurnal variation in atmospheric opacity, due primarily to cloud, on the estimation of daily erythemal UV doses is investigated with both ground-based measurements and ISCCP-D1 data. It is found that daily mean erythemal UV doses estimated from only a noontime satellite “snapshot” may incur errors of more than 20% which is reduced for long-term averages. The products are also compared with other UV products derived solely from the Nimbus-7/TOMS dataset for January and July 1991. Causes for any major discrepancies are investigated.

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