EGU21-7715, updated on 04 Mar 2021
https://doi.org/10.5194/egusphere-egu21-7715
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reconciling different approaches to quantifying surface cooling induced by afforestation in China using satellite observations

Huanhuan Wang1,2, Chao Yue1,2, Sebastiaan Luyssaert3, Jie Zhao1,2, and Hongfei Zhao1,2
Huanhuan Wang et al.
  • 1State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, China
  • 2College of Natural Resources and Environment, Northwest A&F University, China
  • 3Faculty of Science, Vrije Universiteit Amsterdam, Netherlands

Forest cover change can cause strong local biophysical feedbacks on climate. Satellite observations of land surface temperature (T) and land cover distribution or forest cover change have been widely used to examine the effects of afforestation/deforestation on local surface temperature change (ΔT). However, different approaches were used by previous analyses to quantifying ΔT, and it remains unclear whether results of ΔT by these approaches are comparable. We identified three influential approaches to quantifying ΔT used by previous studies, namely the actual ΔT resulting from actual changes in forest coverage over time and accounting for changes in background climate (ΔTa proposed by Alkama and Cescatti, 2016), potential ΔT by hypothesizing potential shifts between non-forest and forest at given native spatial resolutions of satellite products (ΔTp1 by Li et al., 2015), and potential ΔT, but using the singular value decomposition technique to derive ΔT by hypothesizing a shift between a 100% complete non-forest and 100% forest (ΔTp2 by Duveiller et al., 2019). China realized large-scale afforestation making it a suitable test case to compare satellite-based approaches for estimating ΔT following afforestation. We hypothesize that (1) ΔTa depends on the fraction of ground area that’s been afforested (Faff). (2) The relative magnitude between different approaches should be: ΔTa < ΔTp1 < ΔTp2. (3) When ΔTa is extended to a hypothetical case that Faff reaches 100%, it should be comparable to ΔTp1 or ΔTp2. We used multiple satellite observation products to test these hypotheses. The results show that the magnitude of actual daytime surface cooling by afforestation (ΔTa) increases with Faff, and is significantly lower than ΔTp1 and ΔTp2. But no significant difference was found between ΔTp1 and ΔTp2. A linear regression model established between ΔTa and Faff extends the ΔTa, when Faff reaches 100%, to a comparable magnitude than ΔTp1 and ΔTp2. Our study thus highlights the importance to consider the actual surface cooling impact by afforestation projects in contrast to the potential effects, and provides a first study to reconcile different approaches to quantify the land surface temperature change due to afforestation.

How to cite: Wang, H., Yue, C., Luyssaert, S., Zhao, J., and Zhao, H.: Reconciling different approaches to quantifying surface cooling induced by afforestation in China using satellite observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7715, https://doi.org/10.5194/egusphere-egu21-7715, 2021.

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