Flash droughts– the rapid drying of land and intensification of drought conditions—have devasting impacts to natural resources, food supplies, and the economy. Less is currently known about the drivers of flash droughts and their impact on landscape carbon losses. We leverage carbon and water cycle data from NASA OCO-2 and Soil Moisture Active and Passive missions to quantify flash drought impacts on U.S. carbon exchange. On average, pre-onset carbon uptake fully offsets post-onset losses, creating a carbon neutral biosphere over a ±3 month period surrounding flash drought onset. This contrasts with ecosystem models, which underestimate pre-onset uptake and overestimate post-onset loss. Furthermore, spaceborne observations of solar induced fluorescence (SIF) provide a reliable indicator of flash droughts at lead times of 2–3 months, due to feedbacks between vegetation growth and soil water loss. This study is expected to improve understanding of flash drought impacts on carbon exchange, and facilitate flash drought early warning.

中文翻译：

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前期条件减轻了突发干旱事件期间的碳损失

突发干旱——土地迅速干燥和干旱状况加剧——对自然资源、粮食供应和经济造成毁灭性影响。目前人们对突发干旱的驱动因素及其对景观碳损失的影响知之甚少。我们利用 NASA OCO-2 和土壤湿度主动和被动任务的碳和水循环数据来量化突发干旱对美国碳交换的影响。平均而言，突发干旱发生前的碳吸收完全抵消了发生后的损失，在突发干旱发生前后的±3个月内形成了碳中性生物圈。这与生态系统模型形成鲜明对比，生态系统模型低估了发病前的吸收并高估了发病后的损失。此外，由于植被生长和土壤水分流失之间的反馈，太阳诱导荧光（SIF）的星载观测提供了提前 2-3 个月的突发干旱的可靠指标。这项研究预计将增进对突发干旱对碳交换影响的了解，并促进突发干旱预警。