Land-atmosphere feedbacks exacerbate concurrent soil drought and atmospheric aridity

Area of Science:

• Climate Science
• Ecology
• Earth System Science

Background:

• Compound extremes, specifically co-occurring soil drought (low soil moisture) and atmospheric aridity (high vapor pressure deficit), pose significant threats to natural and societal systems.
• These conditions are primary physiological stressors leading to widespread vegetation mortality and reduced carbon uptake by terrestrial ecosystems.

Purpose of the Study:

• To empirically demonstrate the global prevalence of coupled soil moisture and vapor pressure deficit.
• To investigate the role of land-atmosphere feedbacks in exacerbating concurrent soil drought and atmospheric aridity.
• To project future changes in the frequency and intensity of these compound extreme events.

Main Methods:

• Empirical analysis of global soil moisture and vapor pressure deficit data to identify co-occurrence patterns.
• Utilized the Global Land Atmosphere Coupling Experiment (GLACE)-CMIP5 experiment to simulate and analyze land-atmosphere feedbacks.
• Analysis of CMIP5 model projections to assess future trends in compound extreme events.

Main Results:

• A strong negative coupling between soil moisture and vapor pressure deficit was observed globally, indicating a high probability of their co-occurrence.
• Land-atmosphere feedbacks, particularly the feedback of soil drought on the atmosphere, significantly exacerbate concurrent soil drought and atmospheric aridity.
• The soil moisture-precipitation feedback amplifies deficits in both soil moisture and precipitation across most regions.

Conclusions:

• Concurrent soil drought and atmospheric aridity are a widespread phenomenon, intensified by land-atmosphere feedbacks.
• These feedbacks are crucial in driving atmospheric aridity extremes and amplifying moisture deficits.
• CMIP5 models project an increase in the frequency and intensity of these compound extremes throughout the 21st century due to land-atmosphere feedbacks.