Prolonged periods of extremely high temperatures with lack of precipitation mark heatwaves that pose health risks and damage ecosystems via rapid soil water depletion and reduced evaporative cooling. Identifying the conditions for the onset of heatwaves and their effects on land-atmosphere energy and mass fluxes remains a challenge. We propose using the generalized complementary relationship (CR) to estimate actual evaporation from heterogeneous landscapes overlain by different vegetation types (i.e., grasslands and forests) and quantify responses to radiation and air temperature anomalies. A strong correlation between air temperature and sensible heat flux anomalies deduced from FLUXNET data suggests that abrupt exceedances of sensible heat flux above climatological means are indicators for the onset of heatwaves. We capitalize on the coupling between latent and sensible heat fluxes and their links to soil moisture availability within the CR framework to predict anomalous increases in regional sensible heat flux associated with soil water depletion (low precipitation) and extreme evaporative demand (hot air and high radiation). The systematic and energy-constrained framework based on the CR concept provides insights into the triggering and feedbacks associated with heatwaves and hydro-climatic extremes such as regional droughts.

中文翻译：

---

利用实际蒸发量和潜在蒸发量之间的互补关系来诊断热浪的发生

长时间的极端高温和缺乏降水标志着热浪，这些热浪通过土壤水分的快速消耗和蒸发冷却的减少而造成健康风险和破坏生态系统。确定热浪爆发的条件及其对陆地-大气能量和质量通量的影响仍然是一个挑战。我们建议使用广义互补关系 (CR) 来估计不同植被类型（即草原和森林）覆盖的异质景观的实际蒸发量，并量化对辐射和气温异常的响应。从 FLUXNET 数据推导出的气温和感热通量异常之间的强相关性表明，显热通量突然超过气候平均值是热浪开始的指标。我们利用潜热通量和感热通量之间的耦合及其与 CR 框架内土壤水分可用性的联系来预测与土壤水分耗竭（低降水）和极端蒸发需求（热空气和高辐射）相关的区域感热通量的异常增加）。基于 CR 概念的系统和能源约束框架提供了对与热浪和区域干旱等水文气候极端事件相关的触发和反馈的见解。