AI 中文总结
研究阈值衍生环境指数的替代推断，发现零假设施加位置（转换前后）决定推断目标，季节事件集中度显著影响指数分辨率与原生分辨率结论的不一致率，为水文气候指数推断提供实用框架。
AI 中文摘要
阈值衍生环境指数将原生分辨率变量转换为事件指示符和聚合计数，但替代检验可能在此转换之前或之后施加其零假设约束。我们表明，这些选择定义了不同的推断目标。阈值-联结函数表示将时间依赖性与季节事件概率向量分离，并使季节集中度成为显式的实验坐标。在预设的13,500条短记忆月度轨迹基准中，指数分辨率边际与谱替代和受约束的原生分辨率替代产生了强烈不对称的配对结论：1084条轨迹仅在指数分辨率下被拒绝，而仅有16条仅在原生分辨率下被拒绝。在保持预期年事件数固定的同时，将事件概率集中在季节周期内，使仅指数不一致率从4.4%增加到16.2%。在独立实验中，使月度事件概率相等将相应比率从15.9%降低到3.9%；当月度百分位数从独立的30年参考期估计时，缓解效果持续存在。原生分辨率推断在基准零假设下得到校准，但具有强烈依赖于机制的敏感性：最强的预设历史反馈备择假设在固定合成门控下具有30.7%的检测率，而对持续状态备择假设的敏感性显著较低。耦合模型比较计划第六阶段亚马逊干旱月份案例研究无法区分，说明了为何应同时报告零假设位置和设计特定的可检测性。这些结果为阈值衍生的水文气候和环境指数的替代推断提供了实用框架。
英文摘要
Threshold-derived environmental indices convert native-resolution variables into event indicators and aggregated counts, but surrogate tests may impose their null constraints either before or after this transformation. We show that these choices define different inferential targets. A threshold--copula representation separates temporal dependence from the seasonal event-probability vector and makes seasonal concentration an explicit experimental coordinate. In a prespecified benchmark of 13,500 short-memory monthly trajectories, an index-resolution marginal-and-spectrum surrogate and a constrained native-resolution surrogate produced strongly asymmetric paired conclusions: 1084 trajectories rejected only at index resolution, compared with 16 only at native resolution. Holding the expected annual event count fixed while concentrating event probability within the seasonal cycle increased index-only discordance from 4.4\% to 16.2\%. In an independent experiment, equalizing monthly event probability reduced the corresponding rate from 15.9\% to 3.9\%; the mitigation persisted when monthly percentiles were estimated from an independent 30-year reference period. Native-resolution inference was calibrated under the benchmark null but had strongly mechanism-dependent sensitivity: the strongest prespecified history-feedback alternative had a 30.7\% detection rate under the fixed synthetic gate, with substantially lower sensitivity to a persistent-regime alternative. A Coupled Model Intercomparison Project Phase 6 Amazon dry-month case study was non-discriminating, illustrating why null placement and design-specific detectability should be reported together. The results provide a practical framework for surrogate inference on threshold-derived hydroclimatic and environmental indices.
