Recent land cover changes in the Southwestern US lead to an increase in surface temperature
Recent land cover changes in the Southwestern US lead to an increase in surface temperature
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DOI：
10.1016/j.agrformet.2020.108246
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发表时间：
2020-11
影响因子：
6.2
通讯作者：
T. Duman;Cheng‐Wei Huang;M. Litvak
中科院分区：
文献类型：
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作者：
T. Duman;Cheng‐Wei Huang;M. Litvak
近几十年来，大规模土地覆盖变化的增加，特别是对气候驱动的扰动的响应，由于碳源和汇、地表粗糙度和能量通量的改变，有可能影响当地和区域的气候变化。利用观测数据，我们预测了两个最广泛的LCC发生在美国西南部的影响：干旱引起的树木死亡率和灌木侵入草地，对地表温度。我们开发了一种新的能量平衡方法，提取的生物物理响应环境条件，预测结构变化，地表粗糙度和冠层电导LCC后将改变地表温度。这种方法不仅使我们能够解释两个不同环境条件的非相邻研究地点之间观测到的表面温度差异，而且还可以分离生物物理和非生物物理特性对表面温度的贡献。我们的研究结果表明，美国西南部由于灌木入侵和树木死亡而导致的生物物理特性变化（独立于其他环境特性的变化）可能会导致中午表面温度（上午11点至下午2点）增加1至2摄氏度，与森林砍伐后的表面温度变化相当。虽然灌木入侵和树木死亡引起的平均地表温度升高是相似的，但在每种情况下，驱动温度变化的生物物理特性是不同的。树木死亡率的空气动力学传导率的变化是加热的最大贡献者，而减少的水分和冠层传导率驱动灌木入侵后的表面温度的增加。我们还展示了这种白天地表温度的增加如何随着未来气候的变化而进一步加剧，特别是随着西南部土壤水可用性的预期减少。
The increase in large-scale land cover change (LCC) in recent decades, particularly in response to climate-driven disturbances, has potential to impact local and regional changes in climate due to modification of carbon sources and sinks, albedo, surface roughness and energy fluxes. Using observational data, we predict the impact of two of the most extensive LCCs occurring in the Southwestern US: drought-induced tree mortality and shrub encroachment into grasslands, on surface temperature. We developed a new energy balance method that extracts the biophysical responses to environmental conditions, to predict how structural changes in albedo, surface roughness and canopy conductance following LCC will alter surface temperature. This method allows us not only to explain the observed differences in surface temperature between two non-adjacent study sites with different environmental conditions, but also to separate the contribution of biophysical and non-biophysical properties to surface temperature. Our results suggest that changes in biophysical properties due to shrub encroachment and tree mortality in the Southwestern US (independent of changes in other environmental properties) can potentially lead to an increase in midday surface temperature (11AM to 2PM) of 1 to 2 degrees Celsius, comparable to changes in surface temperature following deforestation. Although the average surface temperature increase in response to both shrub encroachment and tree mortality is similar, the biophysical properties driving the temperature change are different in each scenario. Change in aerodynamic conductance following tree mortality is the largest contributor to heating, while reduced albedo and canopy conductance drive the increase in surface temperature following shrub encroachment. We also show how this increase in daytime surface temperature could be further intensified with future climate, especially with the expected reduction in soil water availability in the Southwest.