青藏高原典型草地类型植被覆盖度和地表短波反照率协同变化特征研究

Albedo, considered as a key factor mediating the energy balance on Earth’s surface, has direct implications in studying global and regional climate systems. On the Qinghai-Tibet Plateau -- the heat pump of the East Asian monsoon–the spatiotemporal changes in albedo in responding to the vegetation seasonal changes have not been well quantified. Our previous work demonstrated that the relationships between the land surface albedo and the NDVI(EVI)in the growing season (beginning, middle, ending) is a foundational basis for understanding the land-atmosphere exchange process on the Plateau, which is also essential for revealing the energy land surface balance and the climate change on the alpine region. In this study, we will use an Enhanced Spatio-Temporal Adaptive Reflectance Fusion Model(STARFM)to estimate and validate high spatiotemporal changes of albedo/NDVI (2000-2016) for the three typical plateau grassland types (including alpine meadow, alpine steppe, and alpine desert steppe) in northern Tibetan Plateau by fusing multi-source data. The pixel-based regression analysis on the abledo~NDVI in then three typical grasslands, as well as their temporal and spatial changes, the underlying process, and the interaction mechanisms will be examined. This project will fill the missing data gaps and establish a theoretical guidance for model verification of the Land –Atmosphere coupling system.

地表反照率（albedo）作为制约陆面辐射能收支平衡的关键因子，直接影响区域和全球气候系统。青藏高原作为东亚季风的热泵，其地表albedo对植被覆盖NDVI季节变化的响应模式及调节机制还没有得到足够的了解。探寻地表albedo和NDVI(EVI)随生长季不同时期（初期，中期，末期）协同关系是理解陆表地-气交换过程的基础，对揭示高寒陆表能量平衡和气候变化具有重要意义。本申请以藏北典型草原类型（高寒草甸、高寒草地、高寒荒漠草原）为研究对象，通过时空适应性反射率融合模型(STARFM)对多源数据进行数据同化与挖掘，进而估算长时间(2000-2016)高时空分辨率的陆表albedo/NDVI数据，再利用逐像元回归分析典型草地类型的albedo/NDVI在长时间序列生长季不同阶段的时空格局、变化过程并深入探讨相互影响机制，为青藏高原的陆-气系统模拟与验证提供数据和理论依据。

全球变暖和人类活动双重影响下地表过程在发生着变化，地表覆盖的变化势必影响陆-气之间的能热交换，这无疑会影响全球生态系统生产力及地表过程对气候变化的响应和反馈。地表反照率(albedo)作为表征陆-气太阳辐射和水热交换的关键物理参数，是制约陆-气辐射能和水热收支平衡的关键因子。以往针对albedo的研究主要集中在冰雪覆盖的时空变异对其影响，而针对生长季植被覆盖变化对气候变化的影响程度及响应机制研究较弱，甚至对于不同区域、不同植被地表覆盖的albedo变化对区域气候变化的正负反馈的结论还不一致。本研究探寻陆表地-气交换过程的基础，对揭示高寒陆表能量平衡和气候变化具有重要意义。本申请以藏北典型草原类型（高寒草甸、高寒草地、高寒荒漠草原）为研究对象，通过多源数据的融合进而估算长时间（2000-2016）高时空分辨率的陆表albedo/NDVI数据，再利用逐项元回归分析典型草地类型的albedo/NDVI在长时间序列生长季不同阶段的时空格局。研究结果表明在整个高原NDVI的提升的地方区域albedo显示为显著下降，但是高原植被变化（2000-2016）具有明显的空间异质性。通过利用逐项元回归分析典型草地类型的albedo/NDVI在长时间序列生长季不同阶段的时空格局、变化过程并深入探讨相互影响机制，为青藏高原的陆-气系统模拟与验证提供数据和理论依据。