The Complex Role of Semi-Arid Afforestation-Atmosphere Interactions In Shaping Local Weather

The effects of desert afforestation, such as those used for climate change mitigation, during extreme heat events remain an important yet unresolved question. The well-studied, semi-arid Yatir pine forest, located at the edge of the Negev Desert, provides a unique lens through which we study land surface-atmosphere interactions.

Due to high incoming solar radiation and low albedo, the Yatir Forest's net radiation is higher than in any other eco-region. The massive radiation load is balanced by large sensible heat flux, which can influence the forest microclimate and create a thermal contrast with the surrounding shrubland. These processes, in turn, can affect near-surface atmospheric conditions and boundary-layer dynamics.  

Here, we combine in-situ measurements with high-resolution ICON-LAM simulations to offer new insights into the role of local afforestation in shaping surface weather and boundary-layer dynamics during extreme heat events. The in-situ observations not only describe the forest’s physical and physiological properties but also provide essential inputs for the model, enabling an integrated framework that captures known forest-scale processes and demonstrates their upscaling effects across the region.

Our simulations of a heat wave event from May 20 to May 24, 2019, reveal midday sensible heat flux increases of up to 300 W m⁻² within the forest, resulting in surface (skin) cooling of up to 15 °C, while simultaneously producing warming of up to 2 °C in 2-m air temperature. These contrasts generate pronounced modifications in wind patterns and a distinct forest-induced circulation. Remarkably, this circulation produces strong local instability even under synoptic conditions dominated by harsh subsidence. Our findings underscore the complex and sometimes counterintuitive role of semi-arid afforestation during extreme heat events, with important implications for land-management strategies under different atmospheric forcing regimes.