Instantaneous PAR estimated using long records of daily temperature and rainfall

Photosynthetically active radiation (PAR) is a key variable needed for runn ing process models that describe the functioning of agricultural crops or f orest trees. Actual measured data that covers sufficiently long periods on PAR is usually not available for most research sites. Also, existing data u sually consists of temporal averages, which - given the non-linear response of the photosynthetic rate to PAR are not ideal for estimating photosynthe tic production. The range of daily minimum and maximum temperatures is stro ngly correlated to the intensity of solar radiation. We present a method us ing a statistical relationship between these variables for generating a lon g time series of instantaneous PAR values for a given location. The method thus enables one to use photosynthetic production for analyzing growth on s ites for which measured PAR is not available. (C) 2001 Elsevier Science B.V . All rights reserved.