气候变化背景下黄淮海冬小麦复合干热事件演变及暴露评估

Evolution and Exposure Assessment of Compound Dry-hot Events over Winter Wheat in Huang-Huai-Hai Plain under Climate Change

摘要:

黄淮海平原是我国最大的冬小麦产区,春季生长期内高温与干旱并发的复合干热事件对产量的威胁大于单一致灾因子,但其长期演变及冬小麦承灾体的暴露程度仍缺乏定量刻画。本文基于1981—2024年ERA5-Land逐日再分析数据与WheatMapNCP 30 m逐年冬小麦分布,以标准化降水蒸散指数SPEI-3与逐日历日高温第90百分位阈值在冬小麦春季生长窗内识别复合干热事件,构建频次、持续与强度3维度指标,采用Sen斜率、预白化Mann-Kendall检验、Pettitt突变检验与多组阈值敏感性试验刻画其时空演变,并在IPCC暴露度框架下量化冬小麦暴露。结果表明：麦田加权区域平均频次由1981—2002年的1.52 d增至2003—2024年的4.01 d（约2.6倍）,Sen斜率约0.9 d/(10a),突变年为1999年,9组阈值与多种替代干旱分量方案下趋势方向均不变;加剧主要源于增暖驱动下高温与干旱边缘分布的整体移动,3—6月参考蒸散以7.73 mm/(10a)显著上升并贡献水分亏缺趋势的57.5%,而高温-干旱相依放大因子无显著趋势;复合干热呈南高北低格局,趋势可检出的加剧区集中于中南部麦区,2024年全区1.863×10^7 hm^2冬小麦中约3.34×10^6 hm^2（18%）位于其中,以频次为权重的危险加权暴露由2000—2011年的6.50×10^7 hm^2·d升至2012—2024年的8.37×10^7 hm^2·d但未达显著;国家尺度复合干热频次距平与去趋势相对单产距平呈显著负相关（r=-0.33）,从产出端提供了方向性佐证。中南部麦区是危险与暴露相叠加的重点区域,研究结果可为该区抗逆减灾与适应布局提供依据。

Abstract:

The Huang-Huai-Hai Plain is the largest winter wheat production region in China, where compound dry-hot events during the spring growth period threaten yield more than either hazard alone, yet their long-term evolution and the exposure of winter wheat remain inadequately quantified. Based on ERA5-Land daily reanalysis data for 1981—2024 and the 30 m annual WheatMapNCP winter wheat maps (2000—2024), compound dry-hot events were identified within the spring growth window of winter wheat using the 3-month standardized precipitation evapotranspiration index (SPEI-3) and the calendar-day 90th percentile of daily maximum temperature, and annual indices of frequency, duration and intensity were constructed. Their spatiotemporal evolution was characterized with the Theil-Sen slope, the pre-whitened Mann-Kendall test, the Pettitt change-point test and multi-scheme sensitivity experiments, and winter wheat exposure was quantified under the IPCC exposure framework. The results showed that the wheat-area-weighted regional frequency was increased from 1.52 d in 1981—2002 to 4.01 d in 2003—2024 (about 2.6-fold), with a Theil-Sen slope of about 0.9 d/(10a) and a change point in 1999, and the trend direction remained unchanged under nine threshold combinations and alternative drought components. The intensification was mainly driven by warming-induced shifts of the marginal distributions of heat and drought: March—June reference evapotranspiration was increased significantly by 7.73 mm/(10a) and contributed 57.5% of the trend in the water deficit, whereas the heat-drought dependence amplification factor showed no significant trend. Compound dry-hot events were more frequent in the south than that in the north, and the area with a detectable intensifying trend was concentrated in the central-southern wheat belt;about 3.34×10^6 hm^2 (18%) of the 1.863×10^7 hm^2 of winter wheat in 2024 lay within this intensifying area, and the frequency-weighted hazard exposure rose from 6.50×10^7 hm^2·d in 2000—2011 to 8.37×10^7 hm^2·d in 2012—2024 without reaching statistical significance. At the national scale, the anomaly of compound dry-hot frequency was significantly negatively correlated with the detrended relative anomaly of wheat yield (r=-0.33), providing directional evidence from the production side. The central-southern wheat belt, where hazard and exposure overlap, was the priority area for stress-resistant disaster mitigation and adaptation planning, and these results can provide a basis for such measures.