Prediction of drought occurrence based on the Standardized Precipitation Index and the Markov Chain Model with weights
Values of Standardized Precipitation Index (SPI) are calculated from monthly precipitation data collected from 36 weather stations in Guanzhong Plain and Weibei tablelands. The Markov chain model with weights is applied to predict SPI drought intensity by using standardized self-coefficients as weights. The prediction temporal scales of the model are set to 1 month, 3 months, 6 months, 9 months and 12 months. The results show that this Markov chain model has ability to forecast SPI drought intensity at the five temporal scales. The longer the temporal scale, the better the predication. However, the forecasting ability is weak when there is a sharp change or increasing of drought intensity.