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Maps of Daily Light Integral in Italy


The Daily Light Integral (DLI) is defined as total number of photons of solar radiation with a wavelength between 400 and 700 nanometers (nm) received on a flat surface for a period of 24 hours; the unit is defined in moles per square meter per day: mol/(m²·d).

The wave range of 400–700 nm is the fraction of the spectrum of photosynthetically active electromagnetic radiation (PAR), which is an important factor for plant growth.The knowledge of the DLI will allow better management of greenhouse crops. Every plant has its own DLI needs, and within this on our mind, it will make it possible to predict the possible contribution of artificial light needed to maximize photosynthesis and therefore plant growth; therefore it will be optimized plant growth and also energy savings for farmers.Since each plant requires a different optimal light intensity for its growth (above which growth does not benefit further), the knowledge of the DLI of a certain location and its bias differences of each plant within the different season, the presented maps of DLI show us useful tool to the decision-maker (such as incentive policies, operators and trade associations) to guide the better choices on the most suitable crops in desired location within the minimal energy demand. The correlations between solar irradiation and DLI have been studied, and here it is presented DLI data starting from the global horizontal solar irradiation.

Up to now, there are no available public DLI maps over Italy. ENEA has created national, monthly and annual maps, using its own databases of ground measurements of solar radiation and solar radiation maps for the entire Italian territory at different spatial domain scales (with spatial resolution of 1 per 1 square km).


Maps of monthly averaged Daily Light Integral of Italy (time period 2006÷2020):

January February March April May June
January February March April May June
July August September October November December
July August September October November December



Map of annual Daily Light Integral of Italy (time period 2006÷2020):

(italian, temporarily)


Translation of Italian terms in the maps:

Italia Italy
Mappe del’integrale di luce giornaliera Map of Daily Light Integral
Mese Month
Anno Year
Intervallo orario Time profile
Media annua Yearly average
Gennaio January
Febbraio February
Marzo March
Aprile April
Maggio May
Giugno June
Luglio July
Agosto August
Settembre September
Ottobre October
Novembre November
Dicembre December



"Principles of Radiation Measurement", LI-COR, Lincoln (USA)

I. Alados, I. Foyo-Moreno, L. Alados-Arboledas (1995), "Photosynthetically active radiation: measurements and modelling", Agricultural and Forest Meteorology 78 (1996) 121-131

Ariana P. Torres e Roberto G. Lopez, "Measuring Daily Light Integral in a Greenhouse"

James E. Faust e Joanne Logan (2018), Daily Light Integral: "A Research Review and High-resolution Maps of the United States", American Society for Horticultural Science, HORTSCIENCE 53(9):1250–1257. 2018.

Ana García-Rodríguez, Sol García-Rodríguez, Montserrat Díez-Mediavilla e Cristina Alonso-Tristán (2020), "Photosynthetic Active Radiation, Solar Irradiance and the CIE Standard Sky Classification", Applied Sciences, 2020, 10, 8007; doi:10.3390/app10228007

S. Pashiardis, S.A. Kalogirou e A. Pelengaris (2017), "Characteristics of Photosynthetic Active Radiation (PAR) Through Statistical Analysis at Larnaca", Cyprus, SM Journal of Biometrics & Biostatistics 2017; 2(2): 1009

Kumarasamy Sudhakar, Tulika Srivastava1, Guddy Satpathy1 e Manicam Premalatha (2013), "Modelling and estimation of photosynthetically active incident radiation based on global irradiance in Indian latitudes", International Journal of Energy and Environmental Engineering 2013, 4:21

Wenjun Tang, Jun Qin, Kun Yang, Xiaolei Niu, Xiaotong Zhang, Yu Yu e Xudong Zhu (2013), "Reconstruction of daily photosynthetically active radiation and its trends over China", Journal of Geohpysical Reseacrh: Atmospheres, Vol. 118, 13,292–13,302, doi:10.1002/2013JD020527, 2013

Jose M. Vindel, Rita X. Valenzuela, Ana A. Navarro, Luis F. Zarzalejo, Abel Paz-Gallardo, José A. Souto, Ramón Méndez-Gómez, David Cartelle e Juan J. Casares (2018), "Modeling Photosynthetically Active Radiation from Satellite-Derived Estimations over Mainland Spain", Remote Sens. 2018, 10, 849; doi:10.3390/rs10060849


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