Project Title: Using MODAWEC to generate daily weather data for the EPIC model
Collaborating GEO-BENE partners: Eawag (leader), IIASA, Blackland Research and Extension Center
Background
Although EPIC model has been widely used in agricultural and environmental studies, applications of this model may be limited in the regions where daily weather data are not available.
Data
The weather, soil and management data used in this test case were from a long-term experiment conducted at the Arlington Agricultural Research Station of the University of Wisconsin in the south central Wisconsin.
Methods
To generate daily precipitation, a first-order Markov chain by Nicks (1974) is first used to define the day as wet or dry. In case of a wet day, daily precipitation is generated from a modified exponential equation. The model developed by Richardson (1981) was selected to give first approximations of daily temperature because it simulates temperature that is correlated with rainfall.
Results
A stand-alone MODAWEC model was developed to generate daily precipitation and maximum and minimum temperature from monthly precipitation, maximum and minimum temperature, and wet days. A case study shows that crop yields and ET simulated with the generated daily weather data compare very well with those simulated with the measured daily weather data with low normalized mean square errors.
Status
A paper has been published in Environmental Modelling & Software.
Citation
Liu J., Williams J.R., Wang X., Yang H., 2009. Using MODAWEC to generate daily weather data for the EPIC model. Environmental Modelling & Software 24(5): 655-664.
Figure: The relation between Y1 (crop yield simulated with daily climate data generated by the MODAWTHC model) and Yb (crop yield simulated with measured daily climate data) and between Y2 (crop yield simulated with daily climate data generated by EPIC’s built-in weather generator) and Yb. Each point is for one specific year between 1958 and 1991 at the Arlington Agricultural Research Station in Wisconsin. T3, T5, T7, and T9 are four treatments.