Document Type

Article

Publication Date

4-1-2024

Abstract

A dynamic transition in soil hydrologic states through meteorological variability and terrestrial feedback governs soil-vegetation-climate (SVC) interactions, constrained by critical soil moisture (SM) thresholds. However, observational and scaling constraints limit critical SM threshold estimation at the remote-sensing (RS) footprint scale. Using global surface SM (θRS) from NASA’s Soil Moisture Active Passive (SMAP) satellite, we characterize the seasonal preferential hydrologic states of θRS and derive three tipping characteristics to estimate the intensity (Mean Tipping Depth, (Formula presented.)), frequency (Tipping Count, η), and duration (Mean Tipped Time, (Formula presented.)) of the excursion of θRS from wet- to dry-average conditions. The preferential state provides the seasonally dominant hydrological states of θRS, while tipping characteristics capture the ecosystem linkages of the dynamic transition in θRS hydrologic states. Globally, θRS predominantly exhibits a (unimodal) dry-preferential state, especially over arid/semi-arid drylands and a unimodal wet-preferential θRS state in high-latitude boreal forests and tundra biomes. Prevalence of (bimodal) bistable θRS state overlaps with regions of strong positive SM-precipitation coupling and monsoonal climate in semi-arid/subhumid climates. Seasonal preferential hydrologic states co-vary with the regional variability in plant water stress threshold and land-atmospheric coupling strength. Tipping characteristics of θRS show sensitivity to intra-biome variability in SVC coexistence patterns and display high skill in partitioning global ecoregions. While (Formula presented.) and η are climate-controlled, (Formula presented.) is moderated by soil and vegetation through their influence over θRS drydown during water-limited evapotranspiration. Preferential states and tipping characteristics find applications in quantifying SVC coexistence patterns, climate model diagnosis, and assessing ecosystem sensitivity to climate change.

Publication Source (Journal or Book title)

Water Resources Research

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