Summer Precipitation in the Huaihe River Basins and Relevant Climate Indices

ENSO having significant impacts on global climate changes. Evident relations are found between ENSO and precipitation anomaly changes across the Huaihe River Basins. Besides, impacts on precipitation changes in the Huaihe River Basins can also be expected from PDO, NAO and other climate indices. These influences and related stability of the influence are investigated, and combined effects of these climate indices on seasonal precipitation changes in the Huaihe River Basins are studied. In this case, objectives of this paper are to investigate influences of ENSO, NAO, IOD and PDO on the summer precipitation regimes across the Huaihe River Basins, and related stability of the influence; explore whether ENSO, NAO, IOD and PDO are the dominant influencing factors behind occurrences or intensities of precipitation events across the Huaihe River Basins; and understand how climate indices influence seasonal precipitation changes across the Huaihe River Basins, especially from the viewpoint of water vapor transportation. The result may provide valuable information for improving the long-term forecasting of precipitation using its relationship with ENSO, NAO, IOD and PDO, and will provide important theoretical basis for water resources management and disaster prevention.Based on rotated empirical orthogonal decomposition method (REOF), the relationship between the summer precipitation in the Huaihe River Basins and the El Niño/Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), the Indian Ocean Dipole (IOD), the Pacific Decadal Oscillation (PDO) is analyzed. Influences of individual climatic factor or combined influences of climate factors on summer precipitation in the Huaihe River Basins are discussed.Results indicate that PDO and IOD are the key factors influencing summer precipitation in the Huaihe River Basins, where the PDO is in negative significant correlation with summer precipitation. Strong correlation is found between the REOF time coefficients for the summer precipitation anomaly and the climatic factors, and correlations are persistent and steady. Warm and cool periods of ENSO, NAO, IOD, PDO have different impacts on summer precipitation. Cold periods of IOD, NAO and PDO can trigger significantly increasing trend of summer precipitation in the northern Huaihe River Basins. PDO combined with ENSO, NAO and IOD heavily affects summer precipitation and this influence modifies spatial patterns of summer precipitation under influences of individual climate factor. Combined PDO, ENSO, NAO and IOD have evident impacts on summer precipitation, and evident impacts of these climatic factors are also found on precipitation in the northern Huaihe River Basins, also the upper Huaihe River Basins.