Comparison of daily UV doses estimated from Nimbus 7/TOMS measurements and ground‐based spectroradiometric data

Abstract

Abstract. During recent years, methods have been developed for estimating UV irradiance reaching the Earth's surface using satellite-measured backscattered UV radiances. The NASA-developed method is based on radiative transfer calculations and satellite measurements of parameters affecting UV radiation: extraterrestrial solar irradiance, atmospheric ozone, cloud reflectivity, aerosol amounts, and ground albedo. In this work a comparison is made between daily UV erythemal doses estimated from Nimbus-7/TOMS measurements (from 1991 to May 1993) and those calculated from ground-based spectroradiometer data. Three stations operated by the National Science Foundation were chosen for this comparison: Ushuaia, Argentina (for 573 days), Palmer, Antarctica (for 450 days), and San Diego, California, (for 149 days). These stations were selected to illustrate the differences between ground-based measurements using the same type of instrument, SUV-100 double monochromator spectroradiometers, and satellite When the reflectivity at all three sites is low (no snow), the TOMS irradiance estimate is larger than the SUV-100 measurements consistent with previously analyzed Brewer data at Toronto. The effects of local fog or clouds smaller than the satellite field of view and undetected UV-absorbing aerosols near the ground are discussed. In addition to uncertainties in radiometric calibrations of the spectrometers, none of the SUV-100 data are corrected for deviations of diffuser-transmittance from true cosine response. IntroductionChanges in the Earth's atmosphere caused by anthropogenic and natural pollutants has led to the well-documented decline in ozone and the corresponding small increase in UV irradiance at the Earth's surface at higher latitudes greater than about 40 ø [Herman et al., 1996]. These increases can affect the human health, crop yields, ocean productivity, and materials aging.In addition to the satellite estimation of UV irradiance, there has been a long-term well-established network of ground-based instrumentation. The ground-based network has the advantage that it more accurately represents the local conditions of the region than the currently large-pixel (100 km) estimates from TOMS (total ozone mapping spectrometer). UV radiation at ground level is traditionally measured using a variety of ground-based instruments. However, the network of high-quality ground-based UV instruments is not dense enough for a monitoring of the global distribution of solar UV radiation and is almost completely lacking over the oceans. Because of this limitation, methods using satellite measurements of extraterrestrial solar radiation, atmospheric ozone, cloud reflectivity, aerosol amounts, and ground albedo combined with radiative transfer modeling are needed to estimate the daily global distribution of UV irradiance. It is important that the satellite estimates of surface UV irradiance are validated under the widest set of conditions.The longest continuous time series of satellite-based surface UV data has been calculated using th...

Spatial and temporal UV irradiance and aerosol variability within the area of an OMI satellite pixel

“…Satellite ozone and UV data were exhaustively validated by means of GB measurements, regarding TOMS; (Kalliskota et al, 2000;McKenzie et al, 2001;Krotkov et al, 2001;Fioletov et al, 2002;Meloni et al, 2005;Arola et al, 2005;Kazantzidis et al, 2006) and lately OMI; Ialongo et al, 2008;Weihs et al, 2008;Kazadzis et al, 2009;Buchard et al, 2008). All these validation studies converge to the following conclusions:…”

Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 2: Analysis of site aerosol influence

“…In that work, the OMI Lambertian Equivalent Reflectivity (LER) at 360 nm was used to describe cloud-free conditions. A certain day was classified as cloudfree if LER was lower than 10% (Kalliskota et al, 2000). Thus, 703 (49% of the total days) days were selected as cloud-free.…”

The influence of the spatial resolution of topographic input data on the accuracy of 3-D UV actinic flux and irradiance calculations

“…Clouds often mask the influence of total ozone on UV radiation and may cancel, reduce or enhance the expected UV signal (e.g., Schafer et al, 1996;Sabburg et al, 2003;Calbo et al, 2005). In addition to total ozone and clouds, ground albedo is another significant factor influencing UV radiation, with snow cover and depth being the largest factors affecting the albedo (e.g., Blumthaler and Ambach, 1988;McKenzie et al, 1998;Weihs et al, 1999Weihs et al, , 2001Schmucki and Philipona, 2002), with snow albedo being highly dependent on age and type of snow (e.g., Vanicek et al, 2000;Kalliskota et al, 2000). Moreover, several studies have shown that high surface albedo can lead to an enhancement of UV radiation by up to 70 % or more, with the highest enhancements observed during partly cloudy conditions (e.g., McKenzie et al, 1998;Simic et al, 2011).…”