| Popis: |
【Objective】 Precipitation and evapotranspiration are two important parameters required in hydrological modelling and water resource management. In this paper, we analyzed their temporal variation in the arid area in central Ningxia province. 【Method】 The analysis was based on precipitation and monthly average temperature measured from 1969 to 2020 from six meteorological stations across the area. Spatiotemporal variation in the precipitation and net precipitation (the difference between precipitation and evapotranspiration) was calculated using the Koichiro Takahashi's evapotranspiration formula, climate trend method, Mann-Kendall mutation test and the wavelet cycle analysis. 【Result】 ① The precipitation in northwest and southeast of the area differed considerably, with the precipitation in the former and the latter being 188.0 mm and 304.1 mm, and their associated net precipitation being 17.8 mm and 58.9 mm, respectively. ② Rainfall in the area falls mainly in summer, accounting for 57% of the annual precipitation, while precipitation in the winter is the least, accounting for only 3% of annual precipitation. The net precipitation in spring and winter is lower than that in other seasons. ③ Interannual variation in net precipitation has been in a transition from fluctuations to continued drying in the studied period. The extreme rainfalls were mainly in the southeast, and the net precipitation in the northwest was more abundant before 2013 than after 2013. ④ Trend analysis shows that the annual precipitation and net precipitation in the southeast have increased significantly at 1.539 mm/a and 0.467 mm/a, respectively. In contrast, the precipitation in the northwest had increased at 0.647 mm/a, while the net precipitation had been decreasing at 0.073 mm/a though not at a significant level. Mutation analysis showed an abrupt precipitation change in 2010. ⑤ Precipitation and net precipitation in the studied area showed periodicities of 9, 12~13, 40 a, with their associated oscillating periods being 6, 9 and 25 a, respectively. The net precipitation varied largely, having a greater impact on agriculture and animal husbandry. 【Conclusion】 Precipitation and net precipitation in the southeast is more abundant than in the northwest of the studied area. The magnitude of seasonal annual precipitation and net precipitation are ranked in the order of summer>autumn>spring>winter. Precipitation and net precipitation in the studied area have been increasing over the studied period. |
