Relationship between photosyndietically active radiation and global radiation

Abstract

Global radiation (K) (MJ/m².day) and photosynthetically active radiation (PAR) (E/m².day) measurements were made for 1 year at Pelotas, RS under climatic conditions. The data analysis permitted the development of a linear equation to express the relationship of PAR as a function of K in the form PAR = 2.23 K. Shortwave radiation in the PAR waveband (400-700 nm) was about 47% of solar radiation. It photosynthetically active radiation can be estimated as a function of global radiation (X2.23), with mean relative error of the same order of the measurements error of the two variables.