Green Julia K, Konings Alexandra G, Alemohammad Seyed Hamed, Berry Joseph, Entekhabi Dara, Kolassa Jana, Lee Jung-Eun, Gentine Pierre
Department of Earth and Environmental Engineering, Columbia University, New York, NY.
Department of Earth System Science, Stanford University, Stanford, CA.
Nat Geosci. 2017 May 29;Volume 10(Iss 6):410-414. doi: 10.1038/ngeo2957.
The terrestrial biosphere and atmosphere interact through a series of feedback loops. Variability in terrestrial vegetation growth and phenology can modulate fluxes of water and energy to the atmosphere, and thus affect the climatic conditions that in turn regulate vegetation dynamics. Here we analyze satellite observations of solar-induced fluorescence, precipitation, and radiation using a multivariate statistical technique. We find that biosphere-atmosphere feedbacks are globally widespread and regionally strong: they explain up to 30% of precipitation and surface radiation variance. Substantial biosphere-precipitation feedbacks are often found in regions that are transitional between energy and water limitation, such as semi-arid or monsoonal regions. Substantial biosphere-radiation feedbacks are often present in several moderately wet regions and in the Mediterranean, where precipitation and radiation increase vegetation growth. Enhancement of latent and sensible heat transfer from vegetation accompanies this growth, which increases boundary layer height and convection, affecting cloudiness, and consequently incident surface radiation. Enhanced evapotranspiration can increase moist convection, leading to increased precipitation. Earth system models underestimate these precipitation and radiation feedbacks mainly because they underestimate the biosphere response to radiation and water availability. We conclude that biosphere-atmosphere feedbacks cluster in specific climatic regions that help determine the net CO balance of the biosphere.
陆地生物圈与大气通过一系列反馈回路相互作用。陆地植被生长和物候的变化可以调节向大气输送的水和能量通量，进而影响气候条件，而气候条件又反过来调节植被动态。在此，我们使用多元统计技术分析太阳诱导荧光、降水和辐射的卫星观测数据。我们发现，生物圈 - 大气反馈在全球广泛存在且在区域上很强：它们解释了高达30%的降水和地表辐射变化。大量的生物圈 - 降水反馈通常出现在能量和水分限制的过渡区域，如半干旱或季风区域。大量的生物圈 - 辐射反馈通常存在于几个适度湿润的地区以及地中海地区，在这些地方降水和辐射促进了植被生长。随着这种生长，植被潜热和感热传输增强，这增加了边界层高度和对流，影响云量，进而影响入射地表辐射。增强的蒸散作用可以增加湿对流，导致降水增加。地球系统模型低估了这些降水和辐射反馈，主要是因为它们低估了生物圈对辐射和水分可利用性的响应。我们得出结论，生物圈 - 大气反馈集中在特定的气候区域，这些区域有助于确定生物圈的净碳平衡。
