Key Lab of Guangdong for Utilization of Remote Sensing and Geographical Information System, Guangdong Open Laboratory of Geospatial Information Technology and Application, Guangzhou Institute of Geography, Guangzhou 510070, China; Laboratoire des Sciences du Climat et de l'Environnement, UMR 1572 CEA-CNRS UVSQ, 91191 Gif sur Yvette, France.
Key Lab of Guangdong for Utilization of Remote Sensing and Geographical Information System, Guangdong Open Laboratory of Geospatial Information Technology and Application, Guangzhou Institute of Geography, Guangzhou 510070, China.
Environ Int. 2019 Nov;132:105080. doi: 10.1016/j.envint.2019.105080. Epub 2019 Aug 26.
The well-documented energy balance dynamics within forest ecosystems are poorly implemented in studies of the biophysical effects of forests. This results in limitations to the accurate quantification of forest cooling/warming on local air temperature. Taking into consideration the forest air space, this study proposes a three-layered (canopy, forest air space and soil [CAS]) land surface energy balance model to simulate air temperature within forest spaces (T) and subsequently to evaluate its biophysical effects on forest cooling/warming, i.e., the air temperature gradient (∆T) between the T and air temperature of open spaces (T) (∆T = T - T). We test the model using field data for 23 sites across 10 cities worldwide; the model shows satisfactory performance with the test data. High-latitude forests show greater seasonal dynamics of ∆T, generating considerable cooling of local air temperatures in warm seasons but minimal cooling or even warming effects during cool seasons, while low-latitude tropical forests always exert cooling effects with less interannual variability. The interannual dynamics of ∆T are significantly related to the seasonality of solar geometry and canopy leaf phenology. The differences between forest canopy temperature (T) and T, which are the two most important terms attributed by the CAS model in impacting T, explain a large part of forest cooling and warming (May-July: R = 0.35; November-January: R = 0.51). The novel CAS model provides a feasible way to represent the energy balance within forest ecosystems and to assess its impacts on local air temperatures globally.
森林生态系统中能量平衡动态的已有充分记录，但在研究森林对生物物理的影响时却没有得到很好的应用。这导致对森林冷却/变暖对当地空气温度的准确量化受到限制。考虑到森林空气空间，本研究提出了一个三层（冠层、森林空气空间和土壤[CAS]）陆地表面能量平衡模型，以模拟森林空间内的空气温度（T），并随后评估其对森林冷却/变暖的生物物理影响，即 T 与开放空间空气温度（T）之间的空气温度梯度（∆T）（∆T= T-T）。我们使用全球 10 个城市的 23 个地点的现场数据对模型进行了测试；该模型对测试数据的表现令人满意。高纬度森林表现出更大的 ∆T 季节性动态，在温暖季节会产生较大的当地空气降温效果，但在凉爽季节降温效果较小甚至出现升温效应，而低纬度热带森林则始终具有降温效果，且年际变化较小。∆T 的年际动态与太阳几何形状和冠层叶物候的季节性密切相关。森林冠层温度（T）和 T 之间的差异，这是 CAS 模型中对 T 影响最大的两个最重要的术语，解释了森林冷却和变暖的很大一部分（5 月至 7 月：R=0.35；11 月至 1 月：R=0.51）。新型 CAS 模型为代表森林生态系统的能量平衡并评估其对全球当地空气温度的影响提供了一种可行的方法。
