【摘要】 为应对陕甘宁地区降水不均引发的旱涝风险，揭示降水集中度(PCD)和集中期(PCP)的时空演变规律至关重要。基于1973—2019年的逐日降水数据，采用矢量法计算PCD与PCP，并结合经验正交函数分析(EOF)方法对其时空特征进行定量评估。结果表明:年降水量呈下降趋势(-1.46 mm/10a)，春季下降尤为显著(-3.74 mm/10a)，夏季和冬季则呈上升趋势; EOF第1模态反映了全区的一致性变化，第2模态呈现出“西北-东南反向”的空间分异特征; PCP自西北向东南逐渐推迟，峰值时间由7月下旬延迟至8月上旬。EOF方法解析PCD与PCP的组合模态，揭示了降水集中性的“全区协同-局地分异”的双重特征，为区域洪涝和干旱预警以及差异化的生态管理提供了支撑。更多还原

【Abstract】 Clarifying the spatiotemporal evolution patterns of the precipitation concentration degree( PCD)and precipitation concentration period( PCP) is crucial for the management of flood and drought risks caused by uneven precipitation distribution in the Shaanxi-Gansu-Ningxia Region. Based on daily precipitation data from 1973 to 2019,PCD and PCP were calculated by the vector method,and their spatiotemporal characteristics were quantitatively assessed by the empirical orthogonal function( EOF) analysis. The results indicate that annual precipitation showed a decreasing trend(-1. 46 mm/10a),with the most significant decline in spring(-3. 74 mm/10a),while summer and winter precipitation exhibited increasing trends. The first EOF mode revealed a spatially consistent pattern across the region,while the second mode presented a “northwest-southeast dipole”pattern with opposite variations. The PCP was progressively delayed from the northwest to the southeast,with its peak shifting from late July to early August. This study innovatively integrates EOF analysis with PCD and PCP,revealing the dual characteristics of “holistic coordination and local differentiation”of the precipitation concentration. These findings can provide a theoretical support for regional flood/drought early warning and differentiated ecological management.更多还原