Contrasting impacts of forests on cloud cover based on satellite observations

How forests influence cloud cover in different regions is not well understood. Here, the authors use satellite data to show that forests enhance clouds over most temperate and boreal forests but inhibited clouds over forests of Amazon, Central Africa, and Southeast US relative to nonforest areas. Forests play a pivotal role in regulating climate and sustaining the hydrological cycle. The biophysical impacts of forests on clouds, however, remain unclear. Here, we use satellite data to show that forests in different regions have opposite effects on summer cloud cover. We find enhanced clouds over most temperate and boreal forests but inhibited clouds over Amazon, Central Africa, and Southeast US. The spatial variation in the sign of cloud effects is driven by sensible heating, where cloud enhancement is more likely to occur over forests with larger sensible heat, and cloud inhibition over forests with smaller sensible heat. Ongoing forest cover loss has led to cloud increase over forest loss hotspots in the Amazon (+0.78%), Indonesia (+1.19%), and Southeast US (+ 0.09%), but cloud reduction in East Siberia (-0.20%) from 2002-2018. Our data-driven assessment improves mechanistic understanding of forest-cloud interactions, which remain uncertain in Earth system models.

Automated summary

This study uses satellite data to demonstrate the contrasting effect of forests on summer cloud cover in different regions, with temperate and boreal forests enhancing clouds and forests in the Amazon, Central Africa, and Southeast US inhibiting clouds. The spatial variation in cloud effects is driven by differences in sensible heat.