Prolonged droughts and heatwaves are common causes of agricultural failure in Australia, yet the origins of these climate anomalies remain understudied. Here, we use a Lagrangian trajectory model driven by atmospheric reanalysis and constrained by satellite data to unravel the sources of precipitation and heat over the Southeastern Australia wheat belt. Furthermore, we assess the impact of local and upwind drought conditions on the moisture and heat imports to the region. Results indicate that the most extreme crop failure events over the wheat belt (i.e., 1994, 2002, and 2006) were associated with persistent high-pressure systems. The ocean provided on average 72% of the moisture for precipitation and 39% of the heat arriving over the wheat belt, with the moisture sources substantially decreasing during crop failure events. Upwind drought further intensified rainfall deficits and heat stress during these events due to lower moisture and higher heat imports to the region. This was particularly clear during the initial phase of the Millennium Drought in 2002. Then, yield deficits exceeded 50%, and ∼4% of the precipitation originated from drought-affected regions upwind, compared to the 9% that was expected climatologically from those regions. Simultaneously, the heat import from these regions upwind increased by ∼10 W m⁻², from the climatological 23%–25%, during this event. While these results indicate a limited potential for upwind land management to mitigate downwind agricultural loss in the Southeastern Australia wheat belt, other agricultural regions with a higher climatic dependency on remote land may benefit from such strategies.

中文翻译：

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澳大利亚东南部小麦带农作物歉收期间的高温和潮湿异常

长期干旱和热浪是澳大利亚农业失败的常见原因，但这些气候异常的根源仍未得到充分研究。在这里，我们使用由大气再分析驱动并受卫星数据约束的拉格朗日轨迹模型来揭示澳大利亚东南部小麦带的降水和热量来源。此外，我们评估了当地和逆风干旱条件对该地区水分和热量输入的影响。结果表明，小麦带最极端的农作物歉收事件（即1994年、2002年和2006年）与持续高压系统有关。海洋平均为降水提供了 72% 的水分，为小麦带提供了 39% 的热量，而在农作物歉收期间，水分来源大幅减少。由于该地区水分减少和热量输入增加，逆风干旱进一步加剧了这些事件期间的降雨不足和热应激。这在 2002 年千年干旱的初期尤为明显。随后，产量赤字超过 50%，约 4% 的降水来自受干旱影响的逆风地区，而气候学上预计这些地区的降水量为 9% 。同时，在此事件期间，来自这些逆风区域的热量输入增加了约 10 W m ^-2，从气候学的 23%–25% 增加。虽然这些结果表明，在澳大利亚东南部小麦带，逆风土地管理在减轻顺风农业损失方面的潜力有限，但对偏远土地气候依赖性较高的其他农业地区可能会从此类策略中受益。