Quality and reliable drought prediction is essential for mitigation strategies and planning in disaster-stricken regions globally. Prediction models such as empirical or data-driven models play a fundamental role in forecasting drought. However, selecting a suitable prediction model remains a challenge because of the lack of succinct information available on model performance. Therefore, this review evaluated the best model for drought forecasting and determined which diferences if any were present in model performance using standardised precipitation index (SPI). In addition, the most efective combination of the SPI with its respective timescale and lead time was investigated. The efectiveness of datadriven models was analysed using meta-regression analysis by applying a linear mixed model to the coefcient of determination and the root mean square error of the validated model results. Wavelet-transformed neural networks had superior performance with the highest correlation and minimum error. Preprocessing data to eliminate non-stationarity performed substantially better than did the regular artifcial neural network (ANN) model. Additionally, the best timescale to calculate the SPI was 24 and 12 months and a lead time of 1–3 months provided the most accurate forecasts. Studies from China and Sicily had the most variation based on geographical location as a random efect; while studies from India rendered consistent results overall. Variation in the result can be attributed to geographical diferences, seasonal infuence, incorporation of climate indices and author bias. Conclusively, this review recommends use of the wavelet-based ANN (WANN) model to forecast drought indices.
Peer-reviewed publication