The negative drought impacts on crop yield are well recognized in the literature, but are evaluated mainly in a deterministic manner. Considering the randomness feature of droughts and the compounding effects of other factors, we hypothesize that droughts effects on yields are probabilistic especially for assessment in large geographical regions. Taking US maize yield as an example, we found that a moderate, severe, extreme and exceptional drought event (based on the standardized precipitation evapotranspiration index) would lead to a yield loss risk (i.e. the probability of yield reduction lower than expected value) of 64.3%, 69.9%, 73.6%, and 78.1%, respectively, with hotspots identified in Central and Southeastern US. Irrigation has reduced yield loss risk by 10%–27%, with the benefit magnitude depending on the drought intensity. Evaluations of eight process crop models indicate that they can well reproduce observed drought risks for the country as a whole, but show difficult in capturing the spatial distribution patterns. The results highlight the diverse risk pattern in response to a drought event of specific intensity, and emphasize the need for better representation of drought effects in process models at local scales. The analysis framework developed in this study is novel in that it allows for an event-based assessment of drought effects in a risk manner in both observations and process crop models. Such information is valuable not only for robust decision-makings but also for the insurance sector, which typically require the risk information rather than a single value of outcome especially given the uncertainty of drought effects.

干旱对农作物产量的负面影响在文献中已得到充分认识，但主要是以确定性方式进行评估。考虑到干旱的随机性和其他因素的复合作用，我们假设干旱对产量的影响是概率性的，特别是在大地理区域进行评估时。以美国玉米产量为例，我们发现中度，重度，极端和特殊干旱事件（基于标准的降水蒸散指数）将导致以下情况的单产损失风险（即单产下降的可能性低于预期值）美国中部和东南部发现热点的比例分别为64.3％，69.9％，73.6％和78.1％。灌溉使产量损失风险降低了10％–27％，其受益程度取决于干旱强度。对八种农作物模型的评估表明，它们可以很好地再现整个国家观察到的干旱风险，但显示出难以把握空间分布格局。结果强调了应对特定强度干旱事件的各种风险模式，并强调了需要在局部规模的过程模型中更好地表示干旱影响。在这项研究中开发的分析框架是新颖的，因为它允许在观测和过程作物模型中以风险方式对干旱影响进行基于事件的评估。此类信息不仅对稳健的决策具有价值，对于保险业也非常有用，因为保险业通常需要风险信息，而不是单一的结果值，特别是考虑到干旱影响的不确定性。