Characteristics of extreme precipitation and its sensitivity to regional climate change in the upper and middle reaches of the Yellow River Basin

Abstract

[Objective] Clarifying the regional characteristics and variation trends of extreme precipitation events has great significance for ecological security and disaster mitigation under climate change. [Methods] Based on the observation data from 1961-2020, linear trend analysis, M-K test, Morlet wavelet analysis, and correlation analysis were used to analyze the spatiotemporal variation of extreme precipitation events and their sensitivity to climate change from previous period (1961-1990) and recent period (1991-2020) across the upper and middle Yellow River Basin. [Results] (1) Most extreme precipitation indices decreased first and then increased around the 1990s, except the continuously decreasing consecutive dry days (CDD). In the recent period, average daily rainfall intensity (SDII), rainfall on very wet days (R95), and rainstorm days (R50) significantly rose at 0.43 mm/(d·10a), 13.98 mm/10a, and 0.06 d/10a respectively (p < 0.05). (2) In the whole period, the southwestern part of the study region was relatively wet while the Yellow River bend area was the driest, and the extreme heavy precipitation presented more in the southeast and less in the west. In the recent period, the wetting trend in the upper Yellow River Basin gradually increased, and the frequency and intensity of extreme heavy precipitation in the middle Yellow River Basin increased significantly. (3) The average annual temperature in the upper and middle Yellow River Basin rose by about 1.5 ℃ with the acceleration of the warming rate during the past 60 years. The annual precipitation first decreased and then increased, and the upward trend in the recent period reached the extremely significant level (p < 0.01). The climate of the study region was transforming from warm-dry to warm-wet, especially in the upper part of the basin. Extreme precipitation was more sensitive to the annual precipitation amount than average temperature and had significant positive correlations, except for CDD. [Conclusion] The trends and magnitudes of variation of extreme precipitation events in the previous period and the recent period were much larger than that in the whole period. Since the 1990s, distinct warm-wet trend appeared in the upper reaches, while extreme heavy precipitation events increased significantly in the middle Yellow River Basin, requiring special attention to future floods.

Keywords

• extreme precipitation|spatiotemporal variations|climate change|sensitivity|mann-kendall test|wavelet analysis|the upper and middle reaches of the yellow river basin