Assessment of agricultural basic drought based on projection pursuit

The method of projection pursuit (PP) was presented to assess the agricultural basic drought for solving the problems such as the incompatibility of drought indexes and the rough grade levels assessed by other methods. Based on the grade division standard of agricultural drought, the projection function which could reflect the variability of the agricultural basic drought system was constructed, and free search (FS) was introduced to optimize the function and seek the optimum projection vector, while the data of the vector were used to research the influential level of each drought index. In Gannan County, considered the space-time representativeness of observation data and influential degree of drought indexes on drought assessment, the percentage of precipitation anomalies and the number of days which had no available rainfall were selected to establish assessment model of agricultural basic drought based on projection pursuit. The achieved results suggested that the conclusion assessed by the model was accordant with the factual drought, and the projection pursuit model could identify the grade of agricultural drought clearly. Projection pursuit model is an effective method for assessing the agricultural basic drought.