Validation of daily erythemal doses from Ozone Monitoring Instrument with ground‐based UV measurement data

Abstract

[1] The Dutch-Finnish Ozone Monitoring Instrument (OMI) on board the NASA EOS Aura spacecraft is a nadir viewing spectrometer that measures solar reflected and backscattered light in a selected range of the ultraviolet and visible spectrum. The instrument has a 2600 km wide viewing swath and it is capable of daily, global contiguous mapping. The Finnish Meteorological Institute and NASA Goddard Space Flight Center have developed a surface ultraviolet irradiance algorithm for OMI that produces noontime surface spectral UV irradiance estimates at four wavelengths, noontime erythemal dose rate (UV index), and the erythemal daily dose. The overpass erythemal daily doses derived from OMI data were compared with the daily doses calculated from the ground-based spectral UV measurements from 18 reference instruments. Two alternative methods for the OMI UV algorithm cloud correction were compared: the plane-parallel cloud model method and the method based on Lambertian equivalent reflectivity. The validation results for the two methods showed some differences, but the results do not imply that one method is categorically superior to the other. For flat, snow-free regions with modest loadings of absorbing aerosols or trace gases, the OMI-derived daily erythemal doses have a median overestimation of 0-10%, and some 60 to 80% of the doses are within ±20% from the ground reference. For sites significantly affected by absorbing aerosols or trace gases one expects, and observes, bigger positive bias up to 50%. For high-latitude sites the satellite-derived doses are occasionally up to 50% too small because of unrealistically small climatological surface albedo.

The first estimates of global nucleation mode aerosol concentrations based on satellite measurements

“…Levy et al, 2010) and the OMI UV (e.g. Tanskanen et al, 2007) products have been extensively validated against ground-based measurements.…”

Validity of satellite measurements used for the monitoring of UV radiation risk on health

“…To validate the OMI data, comparisons were done with the UV radiation measured in 18 ground-based stations (Tanskanen et al, 2007). For flat, snow-free regions with modest loadings of absorbing aerosols or trace gases, the OMIderived daily erythemal doses have a median overestimation of 0-10 %, and some 60 to 80 % of the doses are within ±20 % from the ground reference.…”

Trends in erythemal doses at the Polish Polar Station, Hornsund, Svalbard based on the homogenized measurements (1996–2016) and reconstructed data (1983–1995)

“…These include only five of the northernmost stations above 70 • N: Alert (82.5 • N, 62.31 • E), • N, 11.92 • E), Hornsund (77.0 • N,15.33 • E), Resolute (74.72 • N,94.98 • W,and Barrow (71.32 • N, 156.68 • W). The algorithm to calculate the surface UV using the satellite data (total ozone, groundreflectivity) over high-latitude regions sometimes failed due to the fact that the observed high-reflectivity surfaces might be erroneously classified as high ground albedo (from snow and ice cover) or cloud effect (Tanskanen et al, 2007). It is crucial to examine the UV variability over the Arctic regions, especially for high latitudinal coastal sites, because of rich and diverse ecosystems located in this area (Hessen et al, 2001).…”