An empirical model to predict the UV‐index based on solar zenith angles and total ozone

Allaart, Marc; Weele, M. van; Fortuin, P.; Kelder, H.

doi:10.1017/s1350482703001130

Cited by 68 publications

(67 citation statements)

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“…UV radiation data, as midday erythemal irradiance (250-400 nm, weighted), were obtained from the NASA TOMS satellite record for the region upwind of Cape Grim (40-45 • S 110-130 • E) available from http://macuv.gsfc.nasa.gov/. UV irradiance values were also computed using ozone column data for Melbourne (38 • S 14 • E), determined by the Australian Bureau of Meteorology using the empirical model of Allaart et al (2004). For the available overlap of the two UV irradiance records the correlation coefficient of monthly values is r 2 = 0.99 (n = 290).…”

Section: Methods -Site Description and Instrumentsmentioning

confidence: 99%

Cloud condensation nuclei over the Southern Ocean: wind dependence and seasonal cycles

Gras

Keywood

2017

Atmos. Chem. Phys.

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Abstract. Multi-decadal observations of aerosol microphysical properties from regionally representative sites can be used to challenge regional or global numerical models that simulate atmospheric aerosol. Presented here is an analysis of multi-decadal observations at Cape Grim (Australia) that characterise production and removal of the background marine aerosol in the Southern Ocean marine boundary layer (MBL) on both short-term weather-related and underlying seasonal scales.A trimodal aerosol distribution comprises Aitken nuclei (< 100 nm), cloud condensation nuclei (CCN)/accumulation (100-350 nm) and coarse-particle (> 350 nm) modes, with the Aitken mode dominating number concentration. Whilst the integrated particle number in the MBL over the clean Southern Ocean is only weakly dependent on wind speed, the different modes in the aerosol size distribution vary in their relationship with wind speed. The balance between a positive wind dependence in the coarse mode and negative dependence in the accumulation/CCN mode leads to a relatively flat wind dependence in summer and moderately strong positive wind dependence in winter. The changeover in wind dependence of these two modes occurs in a very small size range at the mode intersection, indicative of differences in the balance of production and removal in the coarse and accumulation/CCN modes.Whilst a marine biological source of reduced sulfur appears to dominate CCN concentration over the summer months (December to February), other components contribute to CCN over the full annual cycle. Wind-generated coarse-mode sea salt is an important CCN component year round and is the second-most-important contributor to CCN from autumn through to mid-spring (March to November). A portion of the non-seasonally dependent contributor to CCN can clearly be attributed to wind-generated sea salt, with the remaining part potentially being attributed to longrange-transported material. Under conditions of greater supersaturation, as expected in more convective cyclonic systems and their associated fronts, Aitken mode particles become increasingly important as CCN.

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Section: Methods -Site Description and Instrumentsmentioning

confidence: 99%

Cloud condensation nuclei over the Southern Ocean: wind dependence and seasonal cycles

Gras

Keywood

2017

Atmos. Chem. Phys.

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“…The products are calculated using operational satellite data streams of the global ozone distribution and, over Europe, the diurnal variation in cloud cover fraction. The TEMIS UV data products essentially exploit the empirically based parametrization by Allaart et al (2004) of the amount of UV radiation incident at the surface in W m −2 , as a function of the total ozone column and the solar zenith angle at a given local solar time, taking into account an appropriate action spectrum, i.e., the wavelength-dependent response to UV radiation of health effects or otherwise.…”

Section: Operational Servicesmentioning

confidence: 99%

“…For each action spectrum, a parametrization is applied following Allaart et al (2004) for the UV solar irradiance as a function of SZA(t) and total ozone column providing a first guess of the UV irradiance weighted with a specific action spectrum (UVI ), at time t using the global assimilated ozone field at local solar noon (t = 12 h).…”

Section: Products and Algorithmsmentioning

confidence: 99%

“…= 1/(1−xy), where x = 0.25 is the UV albedo of the overlying atmosphere for upward-reflected UV radiation and y = A g . Since the Allaart et al (2004) UV index parameterization is empirically based on UV data collected at De Bilt and Paramaribo, the A g at these (urban) sites -with a 12-month average value of 0.09 -is used as a normalization factor for the calculation of f A . The data for A g at each UV grid cell are taken at 335 nm from the monthly TOMS/GOME climatology, which uses the spectral dependency of the GOME database (Koelemeijer et al, 2003) but with a scaling to match the TOMS 340/380 nm database (Herman and Celarier, 1997;Boersma et al, 2004).…”

Section: Products and Algorithmsmentioning

confidence: 99%

“…(1) for the variable presence of aerosols in the TEMIS UV data products. However, the Allaart et al (2004) empirically based parametrization includes an implicit aerosol correction due to the average aerosol load over these two urban sites: an aerosol optical depth (AOD) at 368 nm of 0.3 and an aerosol single-scattering albedo (SSA) of 0.9 (Badosa and van Weele, 2002). For situations where the real aerosol load is lower (higher) than the assumed load, the UV data products will underestimate (overestimate) the UV index and UV dose.…”

Section: Products and Algorithmsmentioning

confidence: 99%

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TEMIS UV product validation using NILU-UV ground-based measurements in Thessaloniki, Greece

et al. 2017

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Abstract. This study aims to cross-validate ground-based and satellite-based models of three photobiological UV effective dose products: the Commission Internationale de l'Éclairage (CIE) erythemal UV, the production of vitamin D in the skin, and DNA damage, using high-temporalresolution surface-based measurements of solar UV spectral irradiances from a synergy of instruments and models. The satellite-based Tropospheric Emission Monitoring Internet Service (TEMIS; version 1.4) UV daily dose data products were evaluated over the period 2009 to 2014 with groundbased data from a Norsk Institutt for Luftforskning (NILU)-UV multifilter radiometer located at the northern midlatitude super-site of the Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki (LAP/AUTh), in Greece. For the NILU-UV effective dose rates retrieval algorithm, a neural network (NN) was trained to learn the nonlinear functional relation between NILU-UV irradiances and collocated Brewer-based photobiological effective dose products. Then the algorithm was subjected to sensitivity analysis and validation. The correlation of the NN estimates with target outputs was high (r = 0.988 to 0.990) and with a very low bias (0.000 to 0.011 in absolute units) proving the robustness of the NN algorithm. For further evaluation of the NILU NN-derived products, retrievals of the vitamin D and DNA-damage effective doses from a collocated Yankee Environmental Systems (YES) UVB-1 pyranometer were used. For cloud-free days, differences in the derived UV doses are better than 2 % for all UV dose products, revealing the reference quality of the ground-based UV doses at Thessaloniki from the NILU-UV NN retrievals. The TEMIS UV doses used in this study are derived from ozone measurements by the SCIAMACHY/Envisat and GOME2/MetOp-A satellite instruments, over the European domain in combination with SEVIRI/Meteosat-based diurnal cycle of the cloud cover fraction per 0.5• (lat × long) grid cells. TEMIS UV doses were found to be ∼ 12.5 % higher than the NILU NN estimates but, despite the presence of a visually apparent seasonal pattern, the R 2 values were found to be robustly high and equal to 0.92-0.93 for 1588 all-sky coincidences. These results significantly improve when limiting the dataset to cloud-free days with differences of 0.57 % for the erythemal doses, 1.22 % for the vitamin D doses, and 1.18 % for the DNA-damage doses, with standard deviations of the order of 11-13 %. The improvement of the comparative statistics under cloud-free cases further testifies to the importance of the appropriate consideration of the contribution of clouds in the UV radiation reaching the Earth's surface. For the urban area of Thessaloniki, with highly variable aerosol, the weakness of the implicit aerosol information introduced to the TEMIS UV dose algorithm was revealed by comparison of the datasets to aerosol optical depths at 340 nm as reported by a collocated CIMEL sun photometer, operating in Thessaloniki at LAP/AUTh as part of the NASA Aerosol Robotic Network.

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Toward a New UV Index Diagnostic in the Met Office's Forecast Model

Turner

Manners

Morcrette

et al. 2017

J Adv Model Earth Syst

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The United Kingdom sporadically experiences low ozone events in the spring which can increase UV to harmful levels and is particularly dangerous as sunburn is not expected by the public at this time of year. This study investigates the benefits to the UV Index diagnostic produced by the UM at the Met Office of including either, or both of, a more highly resolved spectrum, and forecasted ozone profiles from the ECMWF CAMS database. Two new configurations of the spectral parameters governing the radiative transfer calculation over the UV region are formulated using the correlated‐k method to give surface fluxes that are within 0.1 UV Index of an accurate reference scheme. Clear‐sky comparisons of modeled fluxes with ground‐based spectral observations at two UK sites (Reading and Chilton) between 2011 and 2015 show that when raw CAMS ozone profiles are included noontime UV indices are always overestimated, by up to 3 UV indices at a low ozone event and up to 1.5 on a clear summer day, suggesting CAMS ozone concentrations are too low. The new spectral parameterizations reduce UV Index biases, apart from when combined with ozone profiles that are significantly underestimated. When the same biases are examined spectrally across the UV region some low biases on low ozone days are found to be the result of compensating errors in different parts of the spectrum. Aerosols are postulated to be an additional source of error if their actual concentrations are higher than those modeled.

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An empirical model to predict the UV‐index based on solar zenith angles and total ozone

Abstract: The clear sky UV-index

Cited by 68 publications

References 13 publications

Cloud condensation nuclei over the Southern Ocean: wind dependence and seasonal cycles

Cloud condensation nuclei over the Southern Ocean: wind dependence and seasonal cycles

TEMIS UV product validation using NILU-UV ground-based measurements in Thessaloniki, Greece

Toward a New UV Index Diagnostic in the Met Office's Forecast Model

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