Screening of predictors and development of a statistical prediction model for flood-season precipitation in North—southern Northeast China

Drought and flood disasters occur frequently in North China, where summer precipitation is under strong influence of the East Asian summer monsoon. Further studies are necessary to analyze predictors of summer precipitation and its seasonal prediction in North China. The first two leading modes of summer (July—August) precipitation in North China during 1981—2020 are the whole anomaly mode and dipole mode obtained by empirical orthogonal function (EOF) analysis. Based on the causality of the information flow method, the predictors of the first two leading modes of summer precipitation in North China are selected first and further screened by multiple stepwise regression, and a statistical prediction model for summer precipitation in North China is then established. Three predictors are selected for the first leading mode, i.e., 5-month-lead sea surface temperature (SST) in the western tropical Indian Ocean, 6-month-lead 850 hPa meridional wind in the West Siberian plain, and 2-month-lead 850 hPa meridional wind in the tropical mid Pacific. Four predictors are selected for the second leading mode, i.e., 2-month-lead SST in the central southern Indian Ocean, 3-month-lead outgoing longwave radiation (OLR) in the Sea of Okhotsk, 2-month-lead 850 hPa meridional wind in the tropical West Pacific, and 9-month-lead North Atlantic Oscillation (NAO). The area averaged time correlation coefficient (TCC) between the reconstructed field based on the hindcast/forecast PCs of the first two modes and observations is 0.46. The pattern correlation coefficient (PCC) between the reconstructed field based on the hindcast/forecast PCs of the first two modes and observations show a large interannual variation, and the 40-year average PCC is 0.35, which is similar to the inter-annual variation of PCC between the reconstructed field based on actual PCs of the first two modes and observations. It is found that the prediction model performs well in the years when the precipitation can be reconstructed by the first two modes. Finally, possible mechanisms for the impacts of these predictors on summer precipitation in North China are preliminarily discussed.