青藏高原区域气候高分辨率模拟新进展

Recent progresses in high-resolution simulation of regional climate over the Tibetan Plateau

  • 摘要: 青藏高原,被誉为“世界屋脊”和“第三极”,其独特的地形产生的热力与动力强迫机制对区域、东亚乃至全球气候都存在显著的作用。在全球变暖愈发严重的背景下,青藏高原暖湿化显著,极端高温和极端降水事件频繁发生,与此同时,积雪明显减少,导致冰川退缩、冻土融化加速、土壤冻结期缩短等现象的发生,气象灾害及其衍生灾害也随之增多,引起国际社会与科学界的广泛关注。然而,全球气候模拟结果在青藏高原表现出显著的不确定性—对地形复杂的青藏高原而言,全球气候模式的空间分辨率粗糙、物理过程表示粗略,难以较好地描述中小尺度的天气气候效应。相比于全球气候模式,区域气候模式具有更高的空间分辨率,能够描绘出更加精细的区域地形特征,例如局部地形、地表条件等,因此更能体现区域气候特征。随着计算机资源和超算能力的提升,区域气候模拟的水平分辨率提高到了对流允许尺度,模式模拟误差也逐渐减小。首先介绍并讨论青藏高原区域气候模拟分辨率的提升及进行评估,指出提高区域气候模型的水平分辨率的确可以在一定程度上更准确地模拟青藏高原的气候特征,尤其是在地形复杂和对流活动频繁的地区,但是仍然需要客观全面的评估;其次,分别从陆面、云量、微物理方案等角度讨论了模式物理过程的改进现状;最后,对青藏高原未来区域气候模拟研究存在的挑战和发展方向展开讨论。

     

    Abstract: The Tibetan Plateau, known as the "Roof of the World" and the "Third Pole," plays a significant role in regional climate, East Asian climate, and even global climate due to the thermal and dynamic forcing mechanisms generated by its unique terrain. Against the backdrop of worsening global warming, the Tibetan Plateau is characterized by an obvious warming and wetting trend, with frequent occurrences of extreme heat and precipitation events. Simultaneously, there has been a notable reduction in snow cover, leading to glacier retreat, accelerated permafrost thawing, and shortened soil freezing periods, which are accompanied by more frequent meteorological and related disasters and attract widespread attention from the international community and scientific community. However, global climate simulations for the Tibetan Plateau show considerable uncertainties. Due to the plateau's complex terrain, global climate models, with their coarse spatial resolution and rudimentary representation of physical processes, cannot accurately capture mesoscale and microscale weather and climate effects. Compared to global climate models, regional climate models have higher spatial resolutions that can better describe detailed regional terrain features such as local topography and surface conditions, and thus can more effectively simulate regional climate characteristics. With advances in computational resources and supercomputing capabilities, the horizontal resolution of regional climate simulations has been improved to the convective-permitting scale, and model simulation errors are greatly reduced. This paper first introduces discussions and evaluations of resolution in regional climate simulations over the Tibetan Plateau, noting that increasing horizontal resolution of regional climate models can indeed improve the accuracy of simulations of climate characteristics over the plateau, especially in regions with complex terrain and frequent convective activities. However, comprehensive and objective evaluations are still needed. Additionally, the paper discusses improvements in model physical processes from perspectives of land surface, cloud cover, and microphysics schemes. Finally, it addresses the challenges and future directions in regional climate simulation over the Tibetan Plateau.

     

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