Assays

To calculate today's daylength and photoperiod. Daylength is calculated following the treatment of Sellers, Physical Climatology,pp 15-16 and Appendix 2. Daylength is calculated with a correction for atmospheric refraction equivalent to 50 minutes of a degree. Photoperiod is calculated assuming that light is perceived until the centre of the sun is 6 degrees below the horizon. This is a submodel of AFRC Wheat 2 model in Simile notation (the XML version will follow shortly). All variables and ...