Experimental study of ratio of PAR to direct integral solar radiation under cloudless conditions

M. Mõttus, J. Ross, M. Sulev

Research output: Contribution to journalArticleScientificpeer-review

24 Citations (Scopus)

Abstract

In comprehensive studies of radiation climate, remote sensing of the environment, radiation regime of plant canopy, photosynthesis and biomass production, data on direct and diffuse radiation are needed separately for integral and photosynthetically active radiation (PAR). For direct solar PAR, unlike for integral radiation, there exist no global networks of radiation measurement stations or standard instruments. Thus for estimating PAR from direct integral solar radiation parametric models are required. For measurement of direct solar PAR, we constructed a new instrument, the phytoactinometer, consisting of a LI-COR quantum sensor and a viewlimiting tube. With this instrument PAR was measured at Tartu Observatory, Estonia, concurrently with measurements with the Yanishevski actinometer during the foliated periods of 1996-2001. The ratio of direct solar PAR to direct integral solar integral radiation Ks was considered a function of the sine of solar height sin h and the atmospheric integral transparency coefficient p2, both of which can be readily obtained from any actinometric measurements. Despite the large dispersion of data due to changes in atmospheric water and aerosol content, a semiempirical relationship between Ks, m = 1/sin h and p2 with R2 = 0.95 and error ±4% was obtained using irradiances averaged over 5 min periods. This model was qualitatively compared with the parametric models of [Agric. For. Meteorol. 78 (1996) 121; 93 (1999) 27]. We also concluded that for calculating Ks, the atmospheric integral transparency coefficient p2 does not adequately describe variations in the optical properties of the atmosphere.

Original languageEnglish
Pages (from-to)161-170
Number of pages10
JournalAgricultural and Forest Meteorology
Volume109
Issue number3
DOIs
Publication statusPublished - 3 Sep 2001
MoE publication typeA1 Journal article-refereed

Fingerprint

photosynthetically active radiation
solar radiation
experimental study
transparency
Estonia
optical properties
aerosols
optical property
remote sensing
irradiance
radiation
biomass production
photosynthesis
observatory
canopy
aerosol
sensor
climate
atmosphere
biomass

Keywords

  • Atmospheric integral transparency coefficient
  • Direct radiation
  • Photosynthetically active radiation
  • Phytoactinometer

Cite this

@article{260934d8d0a248c29429e523e5aa6168,
title = "Experimental study of ratio of PAR to direct integral solar radiation under cloudless conditions",
abstract = "In comprehensive studies of radiation climate, remote sensing of the environment, radiation regime of plant canopy, photosynthesis and biomass production, data on direct and diffuse radiation are needed separately for integral and photosynthetically active radiation (PAR). For direct solar PAR, unlike for integral radiation, there exist no global networks of radiation measurement stations or standard instruments. Thus for estimating PAR from direct integral solar radiation parametric models are required. For measurement of direct solar PAR, we constructed a new instrument, the phytoactinometer, consisting of a LI-COR quantum sensor and a viewlimiting tube. With this instrument PAR was measured at Tartu Observatory, Estonia, concurrently with measurements with the Yanishevski actinometer during the foliated periods of 1996-2001. The ratio of direct solar PAR to direct integral solar integral radiation Ks was considered a function of the sine of solar height sin h and the atmospheric integral transparency coefficient p2, both of which can be readily obtained from any actinometric measurements. Despite the large dispersion of data due to changes in atmospheric water and aerosol content, a semiempirical relationship between Ks, m = 1/sin h and p2 with R2 = 0.95 and error ±4{\%} was obtained using irradiances averaged over 5 min periods. This model was qualitatively compared with the parametric models of [Agric. For. Meteorol. 78 (1996) 121; 93 (1999) 27]. We also concluded that for calculating Ks, the atmospheric integral transparency coefficient p2 does not adequately describe variations in the optical properties of the atmosphere.",
keywords = "Atmospheric integral transparency coefficient, Direct radiation, Photosynthetically active radiation, Phytoactinometer",
author = "M. M{\~o}ttus and J. Ross and M. Sulev",
year = "2001",
month = "9",
day = "3",
doi = "10.1016/S0168-1923(01)00269-6",
language = "English",
volume = "109",
pages = "161--170",
journal = "Agricultural and Forest Meteorology",
issn = "0168-1923",
publisher = "Elsevier",
number = "3",

}

Experimental study of ratio of PAR to direct integral solar radiation under cloudless conditions. / Mõttus, M.; Ross, J.; Sulev, M.

In: Agricultural and Forest Meteorology, Vol. 109, No. 3, 03.09.2001, p. 161-170.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Experimental study of ratio of PAR to direct integral solar radiation under cloudless conditions

AU - Mõttus, M.

AU - Ross, J.

AU - Sulev, M.

PY - 2001/9/3

Y1 - 2001/9/3

N2 - In comprehensive studies of radiation climate, remote sensing of the environment, radiation regime of plant canopy, photosynthesis and biomass production, data on direct and diffuse radiation are needed separately for integral and photosynthetically active radiation (PAR). For direct solar PAR, unlike for integral radiation, there exist no global networks of radiation measurement stations or standard instruments. Thus for estimating PAR from direct integral solar radiation parametric models are required. For measurement of direct solar PAR, we constructed a new instrument, the phytoactinometer, consisting of a LI-COR quantum sensor and a viewlimiting tube. With this instrument PAR was measured at Tartu Observatory, Estonia, concurrently with measurements with the Yanishevski actinometer during the foliated periods of 1996-2001. The ratio of direct solar PAR to direct integral solar integral radiation Ks was considered a function of the sine of solar height sin h and the atmospheric integral transparency coefficient p2, both of which can be readily obtained from any actinometric measurements. Despite the large dispersion of data due to changes in atmospheric water and aerosol content, a semiempirical relationship between Ks, m = 1/sin h and p2 with R2 = 0.95 and error ±4% was obtained using irradiances averaged over 5 min periods. This model was qualitatively compared with the parametric models of [Agric. For. Meteorol. 78 (1996) 121; 93 (1999) 27]. We also concluded that for calculating Ks, the atmospheric integral transparency coefficient p2 does not adequately describe variations in the optical properties of the atmosphere.

AB - In comprehensive studies of radiation climate, remote sensing of the environment, radiation regime of plant canopy, photosynthesis and biomass production, data on direct and diffuse radiation are needed separately for integral and photosynthetically active radiation (PAR). For direct solar PAR, unlike for integral radiation, there exist no global networks of radiation measurement stations or standard instruments. Thus for estimating PAR from direct integral solar radiation parametric models are required. For measurement of direct solar PAR, we constructed a new instrument, the phytoactinometer, consisting of a LI-COR quantum sensor and a viewlimiting tube. With this instrument PAR was measured at Tartu Observatory, Estonia, concurrently with measurements with the Yanishevski actinometer during the foliated periods of 1996-2001. The ratio of direct solar PAR to direct integral solar integral radiation Ks was considered a function of the sine of solar height sin h and the atmospheric integral transparency coefficient p2, both of which can be readily obtained from any actinometric measurements. Despite the large dispersion of data due to changes in atmospheric water and aerosol content, a semiempirical relationship between Ks, m = 1/sin h and p2 with R2 = 0.95 and error ±4% was obtained using irradiances averaged over 5 min periods. This model was qualitatively compared with the parametric models of [Agric. For. Meteorol. 78 (1996) 121; 93 (1999) 27]. We also concluded that for calculating Ks, the atmospheric integral transparency coefficient p2 does not adequately describe variations in the optical properties of the atmosphere.

KW - Atmospheric integral transparency coefficient

KW - Direct radiation

KW - Photosynthetically active radiation

KW - Phytoactinometer

UR - http://www.scopus.com/inward/record.url?scp=0035801877&partnerID=8YFLogxK

U2 - 10.1016/S0168-1923(01)00269-6

DO - 10.1016/S0168-1923(01)00269-6

M3 - Article

VL - 109

SP - 161

EP - 170

JO - Agricultural and Forest Meteorology

JF - Agricultural and Forest Meteorology

SN - 0168-1923

IS - 3

ER -