Preferential Hydrologic States and Tipping Characteristics of Global Surface Soil Moisture

Sehgal, Vinit; Mohanty, Binayak P.

doi:10.22541/essoar.167840001.13313960/v1

Cited by 4 publications

(6 citation statements)

References 93 publications

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“…Global estimates of surface soil texture are accessed from Poggio et al (2021). Global estimates of θ RS preferential hydrologic states, tipping characteristics and other variables discussed in this study are freely available in NetCDF format on HydroShare through Sehgal and Mohanty (2023).…”

Section: Data Availability Statementmentioning

confidence: 99%

Preferential Hydrologic States and Tipping Characteristics of Global Surface Soil Moisture

Sehgal,

Mohanty

2024

Water Resources Research

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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, ), frequency (Tipping Count, η), and duration (Mean Tipped Time, ) 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 and η are climate‐controlled, 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.

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Section: Data Availability Statementmentioning

confidence: 99%

Preferential Hydrologic States and Tipping Characteristics of Global Surface Soil Moisture

Sehgal,

Mohanty

2024

Water Resources Research

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“…The number of frequency peaks was designed to represent the strength of soil moisture seasonality. A unimodal distribution represents weak seasonality under persistently wet or dry climates, whereas a bimodal distribution represents strong seasonality (Sehgal & Mohanty, 2023; Figure 2a,b). However, applications to a wider range of climates showed that bimodal distributions had multiple causes.…”

Section: Case Studies: Challenges Applying Signatures In Large Sample...mentioning

confidence: 99%

When good signatures go bad: Applying hydrologic signatures in large sample studies

McMillan,

Coxon,

Araki

et al. 2023

Hydrological Processes

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Hydrologic signatures are quantitative metrics that describe streamflow statistics and dynamics. Signatures have many applications, including assessing habitat suitability and hydrologic alteration, calibrating and evaluating hydrologic models, defining similarity between watersheds and investigating watershed processes. Increasingly, signatures are being used in large sample studies to guide flow management and modelling at continental scales. Using signatures in studies involving 1000s of watersheds brings new challenges as it becomes impractical to examine signature parameters and behaviour in each watershed. For example, we might wish to check that signatures describing flood event characteristics have correctly identified event periods, that signature values have not been biassed by data errors, or that human and natural influences on signature values have been correctly interpreted. In this commentary, we draw from our collective experience to present case studies where naïve application of signatures fails to correctly identify streamflow dynamics. These include unusual precipitation or flow regimes, data quality issues, and signature use in human‐influenced watersheds. We conclude by providing guidance and recommendations on applying signatures in large sample studies.

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“…These can be inferred from spatial maps of fraction of time a pixel spends in dry or wet regime at any given season. The advantage of such a division is that it naturally advances the widely accepted ideas of preferential states of soil moisture (D'Odorico & Porporato, 2004;Grayson et al, 1997;Sehgal & Mohanty, 2023) and Budyko framework (Budyko, 1974), while forgoing earlier terminology conflicts. Additionally, the division allows for quantification of SM-ET coupling using 𝑑 𝑊 which has extensions to understand corresponding entropy production (described in section 3.4) in SM to ET anomaly transference.…”

Section: A Comprehensive Sm-et Coupling Frameworkmentioning

confidence: 99%

“…Another conjecture from the coupling-aridity tradeoff and entropy production capacity is that for a given amount of flux and land temperature, temperate climates bear the least efficiency compared to other hydroclimates for unit anomaly transference. This could be argued to be most likely due to their bistable nature for soil moisture subsidence (Sehgal & Mohanty, 2023).…”

Section: Lower Bound Of Entropy Production and Its Seasonal Variationsmentioning

confidence: 99%

Thermodynamic Bounds of Terrestrial Water-Energy Coupling and Resiliency in Global Ecosystems

Mishra,

Sehgal,

Mohanty

2023

Preprint

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Increasing climatic variability has resulted in an unprecedented surge in extreme events, pressing global ecosystems towards systematic breakdown. Yet, the resilience of the soil-vegetation-atmosphere (SVA) system to revert to its natural state indicates the existence of energetic barriers forbidding systems from tipping. Observational and theoretical constraints limit our understanding of these energetic barriers which are crucial for assessing ecosystem sensitivity to atmospheric perturbations. We provide a novel coherent theory on the dissipative energy barriers (𝛥e) which decides the resilience potential of an ecosystem. These barriers are manifestation of lower bounds of entropy produced ( Σ *) for unit anomaly transference from soil moisture (SM) to evapotranspiration (ET). Using remote sensing data, we compute these global entropy bounds by introducing a new metric (Wasserstein distance, ) for SM-ET coupling. Quantifying these lower bounds from SM-ET coupling, places terrestrial ecosystems in the hierarchy of dissipative energy states spanning from forested regions to barren lands. Furthermore, we show that the optimization of SM-ET coupling translates to entanglement of water potential gradient (∆ω) between land surface and atmospheric boundary layer, and the resulting memory timescale or residence time (τ). This (τ.∆ω) entanglement propels moisture-rich and moisture-deficit systems in complementary evolutionary pathways in responding to imposed anomalies. As a result, we witness an emergence of coupling-aridity tradeoff with temperate climates operating as least efficient systems for unit SM to ET anomaly transfer. Physical basis, and transferability across space and scale makes this theory a potential benchmark for process improvement in the climate and earth system models.

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Preferential Hydrologic States and Tipping Characteristics of Global Surface Soil Moisture

Abstract: This a preprint and has not been peer reviewed. Data may be preliminary.

Cited by 4 publications

References 93 publications

Preferential Hydrologic States and Tipping Characteristics of Global Surface Soil Moisture

Preferential Hydrologic States and Tipping Characteristics of Global Surface Soil Moisture

When good signatures go bad: Applying hydrologic signatures in large sample studies

Thermodynamic Bounds of Terrestrial Water-Energy Coupling and Resiliency in Global Ecosystems

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