Quantifying overlapping and differing information of global precipitation for GCM forecasts and El Niño–Southern Oscillation

[摘要] While El Niño–Southern Oscillation (ENSO)teleconnection has long been used in statistical precipitation forecasting,global climate models (GCMs) provide increasingly available dynamicalprecipitation forecasts for hydrological modeling and water resources management. It is not yet known to what extent dynamical GCM forecastsprovide new information compared to statistical teleconnection. This paperdevelops a novel set operations of coefficients of determination (SOCD) method to explicitly quantify the overlapping and differing information forGCM forecasts and ENSO teleconnection. Specifically, the intersectionoperation of the coefficient of determination derives the overlappinginformation for GCM forecasts and the Niño3.4 index, and then the difference operation determines the differing information in GCM forecasts (Niño3.4 index) from the Niño3.4 index (GCM forecasts). A case study is devised for the Climate Forecast System version 2 (CFSv2) seasonal forecasts of globalprecipitation in December–January–February. The results show that theoverlapping information for GCM forecasts and the Niño3.4 index is significant for 34.94 % of the global land grid cells, that the differing information in GCM forecasts from the Niño3.4 index is significant for 31.18 % of the grid cells and that the differing information in the Niño3.4 index from GCM forecasts is significant for 11.37 % of the grid cells. These results confirm the effectiveness of GCMs in capturing the ENSO-related variabilityof global precipitation and illustrate where there is room for improvement of GCM forecasts. Furthermore, the bootstrapping significance tests of the three types of information facilitate in total eight patterns to disentangle theclose but divergent associations of GCM forecast correlation skill with ENSO teleconnection.

[学科分类] 妇产科学