一个理论指数,用于理解不同的土地相对湿度趋势在观测,重新分析和模型
Wenyu Zhou1, L Ruby Leung1, Bryce E Harrop1
1Atmospheric, Climate, and Earth Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99354.
概括
土地表面相对湿度 (RH) 由于气温上升和降水增加有限而显著下降. 一个新的指数有助于校准RH数据,并揭示模型低估了这种干燥趋势,表明未来可能更干燥.
科学领域:
- 气候学 气候学 气候学
- 地球上的水气候 地球上的水气候
- 大气科学 大气科学
背景情况:
- 陆地表面相对湿度 (RH) 对于陆地与大气的相互作用至关重要,但历史变化不太清楚.
- 有限的观测,有偏见的再分析和缺乏解释框架阻碍了RH变化分析.
- 现有的方法很难解释影响RH趋势的多种因素.
研究的目的:
- 开发一个解释历史土地RH变化的框架.
- 从重新分析和地球系统模型中校准偏见的RH数据.
- 量化观察和模拟RH趋势的驱动因素.
主要方法:
- 开发了一个基于降水 (P) 的简单指数和独立于RH的修改潜在蒸发透气 (ET*).
- 使用该指数分析1973-2024年间的RH趋势,使用观测,重新分析和气候模型.
- P和ET*对RH变化和模型偏差的量化贡献.
主要成果:
- 从1973年到2024年,土地的RH大幅下降,这是由于ET* (由于变暖) 的增加和最低降水量的增加.
- 重新分析高估了由于过度变暖和降水减少而导致的RH下降.
- 地球系统模型低估了历史的干燥趋势,特别是在亚热带地区,由于降水和大气循环的偏差.
结论:
- P/ET*指数为理解和校准土地RH变化提供了物理基础.
- 模型观察差异表明,人们低估了强制干燥,未来可能比预期更干燥.
- 内部气候变化不太可能解释RH趋势中观察到的模型数据差距.
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