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Relationship between global and diffuse irradiance and their variability in South Africa

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Abstract

Global irradiance is an important natural resource which is fundamental in various processes. Direct observations of components of global irradiance are scarce globally and models are required to improve their spatial coverage. Using a 30-year dataset, this study investigates relationships between measured global irradiance and diffuse irradiance at different periods of the day at both coastal and inland locations in South Africa. Historical hourly global and diffuse irradiance data from seven weather stations representing different climate regions were used to determine correlations of clearness index (KT) and diffuse fraction (K) in the morning and afternoon. Results show that K is inversely related to water vapour pressure deficit. Global and diffuse irradiances are largest and smallest during dry and wet seasons, respectively. Areas that are dry in summer have higher global irradiances and regions that are wet in winter have higher diffuse irradiances during these respective periods. For the same clearness index, the diffuse fraction in the afternoon is larger than in the morning. This suggests that diffuse irradiance is generally greater in the afternoon than in the morning. Models that are commonly used to estimate diffuse irradiance from global irradiance underestimate afternoon irradiances by approximately 10% and overestimate morning irradiances by 4%. The relationship between KT and K established in this study does not generally change in magnitude in the long term. However, future studies can investigate variability of these indices at micro-scales considering also the impact of other attenuating factors such as atmospheric precipitable water depth. Accessibility of atmospheric datasets can assist in improving modelling of global irradiance in South Africa using multivariate techniques.

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References

  • Abal G, Aicardi D, Suarez RA, Laguarda A (2017) Performance of empirical models for diffuse fraction in Uruguay. Sol Energy 141:166–181

    Article  Google Scholar 

  • Aguilar C, Herrero J, Polo MJ (2010) Topographic effects on solar radiation distribution in mountainous watersheds and their influence on reference evapotranspiration estimates at watershed scale. Hydrol Earth Syst Sci 14:2479–2494

    Article  Google Scholar 

  • Al-Rawahi NZ, Zurigat YH, Al-Azri NA (2011) Prediction of hourly solar radiation on horizontal and inclined surfaces for Muscat/Oman. J Eng Res 8(2):19–31

    Article  Google Scholar 

  • Bendix J, Silva B, Roos K, Göttlicher DO, Rollenbeck R, Naub T, Beck E (2010) Model parameterization to simulate and compare the PAR absorption potential of two competing plant species. Int J Biometeorol 54:283–295

    Article  Google Scholar 

  • Bergstrom RW, Pilewskie P, Russell PB, Redemann J, Bond TC, Quinn PK, Sierau B (2007) Spectral absorption properties of atmospheric aerosols. Atmos Chem Phys 7:5937–5943

    Article  Google Scholar 

  • Bindi M, Miglietta F, Zipoli G (1992) Different methods for separating diffuse and direct components of solar radiation and their application in crop growth models. Clim Res 2:47–54

    Article  Google Scholar 

  • Boegman N (1977) Air pollution and the metallurgy industry. J South Afr Inst Min Metall 78(1):8–11

    Google Scholar 

  • Campillo C, Fortes R, Prieto MH. (2012) Solar radiation effect on crop production, solar radiation, Elisha B. Babatunde (Ed.), ISBN: 978-953-51-0384-4, InTech, available from: www.intechopen.com/books/solar-radiation/solar-radiation-effect-on-crop-production

  • Chandel SS, Aggarwal RK (2011) Estimation of hourly solar radiation on horizontal and inclined surfaces in Western Himalayas. SGRE 2:45–55. https://doi.org/10.4236/sgre.2011.21006

    Article  Google Scholar 

  • Chen M, Zhuang Q (2014) Evaluating aerosol direct radiative effects on global terrestrial ecosystem carbon dynamics from 2003 to 2010. Tellus Ser B Chem Phys Meteorol 66(1):21808

    Article  Google Scholar 

  • Chen JM, Liu J, Cihlar J, Goulden ML (1999) Daily canopy photosynthesis model through temporal and spatial scaling for remote sensing applications. Ecol Model 124:99–119

    Article  Google Scholar 

  • Chen Y, Hall A, Liou KN (2006) Application of three-dimensional solar radiative transfer to mountains. J Geophys Res 111:D21111

    Article  Google Scholar 

  • Collares-Pereira M, Rabl A (1979) The average distribution of solar radiation—correlations between diffuse and hemispherical and between daily and hourly values. Sol Energy 22(2):155–164

    Article  Google Scholar 

  • de Castro F, Fetcher N (1998) Three dimensional model of the interception of light by a canopy. Agric For Meteorol 90:215–233

    Article  Google Scholar 

  • Duffie JA, Beckman WA (2013) Solar engineering of thermal processes. John Wiley & Sons Inc.,Hoboken

  • Erbs DG, Klein SA, Duffie JA (1982) Estimation of the diffuse radiation fraction for hourly, daily, and monthly-average global radiation. Sol Energy 28(4):293–302

    Article  Google Scholar 

  • Federico S, Torcasio RC, Sano P, Casella D, Campanelli M, Meirink JF, Wang P, Vergari S, Diemoz H, Dietrich S (2017) Comparison of hourly surface downwelling solar radiation estimated from MSG-SEVIRI and forecast by the RAMS model with pyranometers over Italy. Atmos Meas Tech 10:2337–2352

    Article  Google Scholar 

  • Ge S, Smith RG, Jacovides CP, Kramer MG, Carruthers RI (2011) Dynamics of photosynthesis photon flux density (PPFD) and estimates in coastal northern California. Theor Appl Climatol 105:107–118

    Article  Google Scholar 

  • Gopinathan KK (1991) Solar radiation on variously oriented sloping surfaces. Sol Energy 47(3):173–179

    Article  Google Scholar 

  • Gueymard CA (2001) Parameterized transmittance model for direct beam and circumsolar spectral irradiance. Sol Energy 71(5):325–346

    Article  Google Scholar 

  • Held G, Snyman GM, Scheifinger H (1993) Seasonal variation and trends of atmospheric particulates on the South African Highveld: 1982-1990. Clean Air J 8(8):4–11

    Google Scholar 

  • Hofmann M, Seckmeyer G (2017) A new model for estimating the diffuse fraction of solar irradiance for photovoltaic system simulations. Energies 10:248

    Article  Google Scholar 

  • Kamali GA, Moradi I, Khalili A (2006) Estimating solar radiation on tilted surfaces with various orientations: a study case in Karaj (Iran). Theor Appl Climatol 84:235–241

    Article  Google Scholar 

  • Koyama K, Takemoto S (2014) Morning reduction of photosynthetic capacity before midday depression. Sci Rep 4(4389):1–6

    Google Scholar 

  • Li T, Yang Q (2015) Advantages of diffuse light for horticultural production and perspectives for further research. Front Plant Sci 6(704):1–5

    Google Scholar 

  • Linares-Rodriguez A, Ruiz-Arias JA, Pozo-Vazquez D, Tovar-Pescador J (2013) An artificial neural network ensemble model for estimating global solar radiation from Meteosat satellite images. Energy 61:636–645

    Article  Google Scholar 

  • Linguet L, Pousset Y, Olivier C (2016) Identifying statistical properties of solar radiation models by using information criteria. Sol Energy 132:236–246

    Article  Google Scholar 

  • Lizaso JI, Batchelor WD, Boote KJ, Westgate ME (2005) Development of a leaf-level canopy assimilation model for CERES-maize. Agron J 97:22–733

    Google Scholar 

  • Loutzenhiser PG, Manz H, Felsmann C, Strachan PA, Frank T, Maxwell GM (2007) Empirical validation of models to compute solar irradiance on inclined surfaces for building energy simulation. Sol Energy 81:254–267

    Article  Google Scholar 

  • Magi BI (2009) Chemical apportionment of southern African aerosol mass and optical depth. Atmos Chem Phys 9:7643–7655

    Article  Google Scholar 

  • Marpaung F, Hirano T (2014) Environmental dependence and seasonal variation of diffuse solar radiation in tropical peatland. J Agric Meteorol 70(4):223–232

    Article  Google Scholar 

  • Mavi HS, Tupper GJ (2004) Agrometeorology—principles and applications of climate studies in agriculture. Haworth Press, New York

    Book  Google Scholar 

  • Molina A, Favley M, Rondanelli (2017) A solar radiation database for Chile. Nat Sci Rep 7:14823

    Article  Google Scholar 

  • Molineaux B, Ineichen P, Delaunay JJ (1995) Direct luminous efficacy and atmospheric turbidity—improving model performance. Sol Energy 55(2):125–137

    Google Scholar 

  • Orgill JF, Hollands KGT (1977) Correlation equation for hourly diffuse radiation on a horizontal surface. Sol Energy 19:357–359

    Article  Google Scholar 

  • Power HC, Goyal A (2003) Comparison of aerosol and climate variability over Germany and South Africa. Int J Climatol 23:921–941

    Article  Google Scholar 

  • Power HC, Mills DM (2005) Solar radiation climate change over southern Africa and an assessment of the radiative impact of volcanic eruptions. Int J Climatol 25:295–318

    Article  Google Scholar 

  • Power HC, Willmott CJ (2001) Seasonal and interannual variability in atmospheric turbidity over South Africa. Int J Climatol 21:579–591

    Article  Google Scholar 

  • Rehman S, Mohandes M (2008) Artificial neural network estimation of global solar radiation using air temperature and relative humidity. Energy Policy 36:571–576

    Article  Google Scholar 

  • Rouault M, Richard Y (2003) Intensity and spatial extension of drought in South Africa at different time scales. Water SA 29(4):489–500

    Google Scholar 

  • Rumbayan M, Abudureyimu A, Nagasaka K (2012) Mapping of solar energy potential in Indonesia using artificial neural network and geographical information system. Renew Sust Energ Rev 16:1437–1449

    Article  Google Scholar 

  • Sanchez G, Serrano A, Cancillo ML (2017) Modelling the erythemal surface diffuse irradiance fraction for Badajoz, Spain. Atmos Chem Phys 17:12697–12708

    Article  Google Scholar 

  • Senkal O, Kuleli T (2009) Estimation of solar radiation over Turkey using artificial neural network and satellite data. Appl Energy 86:1222–1228

    Article  Google Scholar 

  • Soares J, Oliveira AP, Boznar MZ, Mlakar P, Escobedo JF, Machado AJ (2004) Modelling hourly diffuse solar radiation in the city of Sao Paulo using a neural-network technique. Appl Energy 79:201–214

    Article  Google Scholar 

  • Spitters CJT, Toussaint HAJM, Goudriaan J (1986) Separating the diffuse and direct component of global radiation and its implications for modeling canopy photosynthesis part I. Components of incoming radiation. Agric For Meteorol 38:217–229

    Article  Google Scholar 

  • Tadross M, Johnston P (2012) Climate systems regional report: Southern Africa. Local governments for sustainability—Africa climate systems regional report: Southern Africa, ISBN: 978–0–9921794-6-5

  • Takenaka H, Nakajima TY, Higurashi A, Higuchi A, Takamura T, Pinker RT, Nakajima T (2011) Estimation of solar irradiance using a neural network based on radiative transfer. J Geophys Res 116:D08215

    Article  Google Scholar 

  • Tesfaye M, Botai J, Sivakumar V, Tsidu GM (2014) Simulation of biomass burning aerosols mass distributions and their direct and semi-direct effects over South Africa using a regional climate model. Meteorog Atmos Phys 125:177–195

    Article  Google Scholar 

  • Tsubo M, Walker S (2003) Relationship between diffuse and global solar radiation in Southern Africa. S Afr J Sci 99:360–362

    Google Scholar 

  • Tyson PD, Garstang M, Swap R (1996) Large-scale recirculation of air over southern Africa. J Appl Meteorol 35:2218–2236

    Article  Google Scholar 

  • Ueyama H (2005) Estimating hourly direct and diffuse solar radiation for the compilation of solar radiation distribution maps. J Agric Meteorol 61(4):207–216

    Article  Google Scholar 

  • Walker NJ, Schulze RE (2008) Climate change impacts on agro-ecosystem sustainability across three climate regions in the maize belt of South Africa. Agric Ecosyst Environ 124:114–124

    Article  Google Scholar 

  • Wang Q, Tenhunen J, Schmidt M, Otieno D, Kolcun O, Droesler M (2005) Diffuse PAR irradiance under clear skies in complex alpine terrain. Agric For Meteorol 128:1–15

    Article  Google Scholar 

  • Wang Q, Tenhunen J, Schmidt M, Kolcun O, Droesler M (2006a) A model to estimate global radiation in complex terrain. Bound-Layer Meteorol 119:409–429

    Article  Google Scholar 

  • Wang Q, Tenhunen J, Schmidt M, Kolcun O, Droesler M, Reichstein M (2006b) Estimation of total, direct and diffuse PAR under clear skies in complex alpine terrain of the National Park Berchtesgaden, Germany. Ecol Model 196:149–162

    Article  Google Scholar 

Download references

Acknowledgements

Historical hourly global and diffuse irradiance data were obtained from the South African Weather Service (www.weathersa.co.za). Mr. Sabelo Mazibuko of the Agricultural Research Council, Pretoria assisted with Fig. 1.

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Authors and Affiliations

  1. Soil-Plant-Atmosphere Continuum Research Unit, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, South Africa

    Mphethe I. Tongwane, Michael J. Savage & Mitsuru Tsubo

  2. Agricultural Research Council – Institute for Soil, Climate and Water, Private Bag X79, Pretoria, 0001, South Africa

    Mphethe I. Tongwane & Mitsuru Tsubo

  3. Arid Land Research Center, Tottori University, Tottori, Japan

    Mitsuru Tsubo

Authors
  1. Mphethe I. Tongwane
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  2. Michael J. Savage
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  3. Mitsuru Tsubo
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Correspondence to Mphethe I. Tongwane.

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Highlights

• Empirical models that are used to calculate diffuse solar irradiance from global solar irradiance need to consider separating morning and afternoon times of the day.

• Daily relationships between clearness index and diffuse fraction underestimates (overestimates) afternoon (morning) diffuse irradiance.

• Accuracy of empirical models is improved when estimating diffuse irradiances at longer time scales and models are location specific.

• Clearness index and diffuse fraction depend on water vapour pressure deficit.

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Tongwane, M.I., Savage, M.J. & Tsubo, M. Relationship between global and diffuse irradiance and their variability in South Africa. Theor Appl Climatol 137, 1027–1040 (2019). https://doi.org/10.1007/s00704-018-2646-7

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  • DOI: https://doi.org/10.1007/s00704-018-2646-7

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