Abstract
Seasonal forecasts from dynamical models are expected to be useful for drought predictions in many regions. This study investigated the usefulness of the Climate Forecast System version 2 (CFSv2) in improving meteorological drought prediction in China based on its 25-year reforecast. The six-month standard precipitation index (SPI6) was used as the drought indicator, and its persistence forecast served as the benchmark against which CFSv2 forecasts were evaluated. The analysis found that the SPI6 persistence forecast shows good skills in all regions at short lead times, and CFSv2 forecast can further improve those skills in most regions. The improvement is particularly pronounced at longer lead times and over the humid regions in the southeast. This study also examined the seasonality and regionality of persistence forecast skills and CFSv2 contributions, and reveals regions where CFSv2 forecast shows no or sometimes even negative contributions.
Highlights
Drought is a major type of natural hazard in China that has historically affected many parts of the country
This paper presents an evaluation of the seasonal forecasts from the National Centers for Environmental Prediction (NCEP) Climate Forecast System version 2 (CFSv2) model over China with a focus on its ability to outperform the SPI6 persistence forecast that is solely based on historical observations
Taking 25-year (1982-2006) CFSv2 reforecast dataset and observed monthly precipitation analysis, we quantified the contribution of the CFSv2 model to improving drought forecast skills upon persistence forecast using the correlation coefficient, root mean square error (RMSE) and their skill scores
Summary
Drought is a major type of natural hazard in China that has historically affected many parts of the country. Water 2020, 12, 2010 reach zero at a three-month lead time, and for the SPI6 reaches zero at a six-month lead time, and so on These persistence characteristics of SPI are modulated by a region’s seasonal cycle of precipitation and its inter-annual variability. In order to advance the seasonal hydrological and drought prediction capability in China, it is critical to identify the strength and weakness in the dynamical seasonal forecast, and to understand the seasonality and regionality associated with their forecast skills. Previous studies, such as Mo and Lyon [16], have tackled similar questions in the global domain, but regional-focused studies are still needed to provide more detailed analysis. (1) how skillful the persistence forecast is for drought prediction in China; (2) how much improvement the CFSv2 forecast can contribute to the overall drought forecast skill; (3) how such improvements vary geographically and with season and lead time; (4) whether there are situations under which CFSv2 forecasts show no or even negative contributions to drought forecast skills
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