Irrigation induced surface cooling in the context of modern and increased greenhouse gas forcing
Irrigation induced surface cooling in the context of modern and increased greenhouse gas forcing
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DOI：
10.1007/s00382-010-0932-x
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发表时间：
2011-10
期刊：
影响因子：
4.6
通讯作者：
B. Cook;M. Puma;N. Krakauer
中科院分区：
文献类型：
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作者：
B. Cook;M. Puma;N. Krakauer
有证据表明，温室气体（GHG）强迫增加的预期变暖趋势已被灌溉引起的冷却局部“掩盖”，目前还不确定这种灌溉掩盖效应的大小将在未来发生变化。使用一个灌溉数据集集成到全球大气环流模式，我们研究了现代（2000年）和增加（A1B情景，2050年）的温室气体强迫下，在这两种情况下，使用现代灌溉率灌溉引起的冷却的平衡幅度。在现代情景中，北美、印度、中东和东亚的降温幅度最大。在温室气体强迫增加的情况下，这种冷却效应在北美基本消失，在印度保持相对不变，在中国和中东部分地区加剧。对于北美，灌溉显着增加现代温室气体强迫下的降水，这种降水增强在很大程度上消失在A1B强迫下，减少总潜热通量和整体灌溉冷却效果。在印度，灌溉率足够高，以跟上增加温室气体强迫增加的蒸发需求，并保持冷却的幅度。在中国，温室气体强迫减少降水，并将该地区转移到一个干燥的蒸发制度，导致相对增加的影响，额外的水从灌溉对地表能量平衡。在温室气体强迫增加的情况下，灌溉增加了中东地区的降水，增加了总潜热通量，增强了灌溉冷却效应。最终，灌溉将在多大程度上继续补偿温室气体强迫增加造成的变暖，主要取决于背景蒸发状况的变化、二次灌溉效应（如云、降水）以及社会维持（或增加）当前灌溉率的能力。
There is evidence that expected warming trends from increased greenhouse gas (GHG) forcing have been locally ‘masked’ by irrigation induced cooling, and it is uncertain how the magnitude of this irrigation masking effect will change in the future. Using an irrigation dataset integrated into a global general circulation model, we investigate the equilibrium magnitude of irrigation induced cooling under modern (Year 2000) and increased (A1B Scenario, Year 2050) GHG forcing, using modern irrigation rates in both scenarios. For the modern scenario, the cooling is largest over North America, India, the Middle East, and East Asia. Under increased GHG forcing, this cooling effect largely disappears over North America, remains relatively unchanged over India, and intensifies over parts of China and the Middle East. For North America, irrigation significantly increases precipitation under modern GHG forcing; this precipitation enhancement largely disappears under A1B forcing, reducing total latent heat fluxes and the overall irrigation cooling effect. Over India, irrigation rates are high enough to keep pace with increased evaporative demand from the increased GHG forcing and the magnitude of the cooling is maintained. Over China, GHG forcing reduces precipitation and shifts the region to a drier evaporative regime, leading to a relatively increased impact of additional water from irrigation on the surface energy balance. Irrigation enhances precipitation in the Middle East under increased GHG forcing, increasing total latent heat fluxes and enhancing the irrigation cooling effect. Ultimately, the extent to which irrigation will continue to compensate for the warming from increased GHG forcing will primarily depend on changes in the background evaporative regime, secondary irrigation effects (e.g. clouds, precipitation), and the ability of societies to maintain (or increase) current irrigation rates.