Inaccuracies in weather data and their effects on crop growth simulation results. II. Water-limited production

Abstract

In weather data sets used by crop modellers irregularities occur as inaccuracies in given data and as missing values. The effects of irregularities in temperature and global radiation data on potential production of spring wheat were discussed previously. Here the effects of irregularities in weather data on simulated water-limited production of spring wheat are examined, using the same methods as described previously. In general the crop growth model used was not sensitive to inaccuracies in vapour pressure data and wind speed and average data for these variables could be used to replace missing values. The sensitivity of the model to inaccuracies in other weather data depended on the amount of water available to the crop. In dry years the model was sensitive to inaccuracies in precipitation and radiation data but less so to inaccuracies in air temperature. When water was not limiting the model was not sensitive to inaccuracies in precipitation, but was sensitive to inaccuracies in temperature and radiation data. Use of average values for temperature and global radiation led to large deviations in simulation results. For all variables except precipitation, data from a nearby weather station represented good estimates for missing values. Rainfall data for estimations should be obtained from a site in the immediate vicinity. However, when the complete data set (i.e. for all weather variables) from a station 40 km away was used as input for the model, deviations of up to 2 t ha-1 (= 30%) in simulated yields were found.