A model for diurnal variation in soil and air temperature

A model for predicting diurnal changes in soil and air temperatures given the maximum and minimum temperatures has been developed. The model uses a truncated sine wave to predict daytime temperature changes and an exponential function to predict nighttime temperatures. The model is based upon hourly soil and air temperatures for 1977 at a shortgrass prairie site and is parameterized for 150-cm and 10-cm air temperatures and for soil-surface and 10-cm soil temperatures. The absolute mean error for the model ranged from a maximum of 2.64°C for the 10-cm air temperature to a minimum of 1.20°C for the 10-cm soil temperature. The model was also parameterized for hourly air temperature data for Denver, Colorado. Comparison of the model with other models showed that it did a superior job of fitting the data with a smaller number of parameters.