Abstract:

To explore the non-uniform distribution characteristics and variation patterns of annual precipitation in the middle reaches of the Yellow River, based on the CN05.1 gridded daily precipitation data and the NCEP/NCAR reanalysis data, the paper studied the variation characteristics of the precipitation concentration index (PCI) in the middle reaches of the Yellow River, the correlation between PCI and precipitation and the circulation background differences of the years with abnormal PCI by employing the methods such as correlation analysis and synthesis analysis. The results showed that the PCI in the middle reaches of the Yellow River increased from south to north, which was opposite to the distribution pattern of annual precipitation; the PCI of the basin was most closely related to the precipitation during midsummer (July-August); the precipitation during midsummer in the years with abnormal high PCI was generally above average, while the opposite was true for years with abnormally low PCI; the PCI of the basin was significantly positively correlated with the annual extreme precipitation days and the annual extreme precipitation amount, indicating that the more concentrated the annual precipitation was, the higher the possibility of extreme precipitation would be; there were significant differences in the circulation background during midsummer between years with abnormal high PCI and years with abnormal low PCI, the potential height anomaly field in the mid-high latitudes of Asia for the two cases showed opposite distribution patterns. The northwestern pacific subtropical high during midsummer in the years with extremely high PCI was significantly stronger and simultaneously located more western and northern compared with that in the years with extremely low PCI, which was conducive to abnormal excessive precipitation. In short, the research findings contribute to a more comprehensive scientific understanding of the precipitation distribution patterns in the middle reaches of the Yellow River, while also provide a scientific reference for water resource utilization, agricultural production, and disaster prevention and reduction in the region.

Key words: precipitation concentration, spatial and temporal change, atmospheric circulation, extreme precipitation, middle reaches of the Yellow River, water resource utilization