Editing Drought severity index

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{| class="wikitable" style="float:right; clear:right; margin:0 0 1em 1em; width:320px;"
|+ SIGNAL Earth Structured Data
|-
! Object type
| Damage Signal
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! SIGNAL Earth ID
| DS-00712
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! Observable type
| Drought severity index
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! Unit
| unitless / index or declared physical unit (Provisional unit carried from Step 2 DS-to-OT cleanup review; requires later OT curation if source-specific units diverge.)
|-
! Temporal structure
| —
|-
! Monitoring backbone
| —
|}
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The drought severity index is a quantitative indicator used to characterize the intensity and extent of drought conditions within a defined spatial or administrative unit. It serves as a state-form measure, providing a snapshot of drought severity without incorporating temporal trends or spatial clustering effects. This index is instrumental in understanding the current drought status, aiding in environmental monitoring and resource management decisions.

Droughts represent complex environmental phenomena involving prolonged periods of deficient precipitation, leading to water scarcity and impacts on ecosystems, agriculture, and human activities. The drought severity index contributes to the broader assessment of drought impacts by offering a standardized metric that reflects the energy balance and heat dynamics influencing drought conditions.

Within the context of global environmental monitoring, the drought severity index complements other hydrological and ecological indicators, facilitating integrated assessments of drought stress and its consequences across diverse geographic regions and climatic zones.

== Geographic / System Context ==
The drought severity index is not confined to a specific geographic region, allowing its application across various spatial scales and environmental settings. It can be adapted to local, regional, or broader geographic units depending on monitoring needs. Drought conditions vary widely depending on climatic patterns, land use, and hydrological characteristics, making the index a versatile tool for assessing drought severity in diverse landscapes including arid, semi-arid, and humid environments.

By providing a consistent framework for drought severity assessment, the index supports comparative analyses across different geographic contexts, aiding in understanding spatial variability and the localized impacts of drought phenomena.

== Monitoring and Measurement ==
Monitoring of drought severity typically involves the integration of meteorological, hydrological, and remote sensing data. Observational inputs may include precipitation records, temperature measurements, soil moisture content, and evapotranspiration rates, among others. Institutions such as the National Oceanic and Atmospheric Administration ([https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration NOAA]) and the National Drought Mitigation Center contribute to the development and dissemination of drought indices through comprehensive data collection and analysis.

Measurement conventions for drought indices often rely on standardized datasets and methodologies to ensure comparability and reliability. Remote sensing technologies provide spatially extensive observations that complement ground-based measurements, enhancing the capacity to monitor drought conditions in near real-time and over large areas.

Within the SIGNAL system, this phenomenon is treated as a defined environmental signal whose boundaries and measurement conventions are described below.

== Signal Definition ==
The drought severity index is defined as a unitless or physically declared index representing the current severity of drought conditions within a specified spatial unit. It quantifies the state of drought without embedding rolling temporal trends or spatial clustering, focusing instead on the immediate drought status as influenced by the energy balance and heat dynamics of the environment.

== Boundary Conditions ==
Boundary inclusions for the drought severity index encompass all relevant environmental and climatic factors that contribute to drought severity within the declared spatial unit, including precipitation deficits, temperature anomalies, soil moisture deficits, and evapotranspiration rates. Exclusions involve temporal trend analyses and spatial clustering effects, which are intentionally omitted to maintain the index as a state-form indicator rather than a dynamic or aggregated measure. The index does not incorporate indirect or secondary impacts such as economic losses or social vulnerability.

== Aggregation Semantics ==
Geographically, the drought severity index can be aggregated across various spatial scales, from local to regional or national levels, depending on the monitoring framework. Temporal aggregation is not embedded within the index itself, as it represents a state measure at a given time rather than a cumulative or trend-based metric. Cross-signal aggregation may involve integrating the drought severity index with related environmental signals such as burned area, crop heat stress days, and net primary productivity to provide a comprehensive understanding of drought impacts and ecosystem responses. Aggregation notes emphasize the importance of maintaining consistency in spatial units and temporal reference points when combining or comparing index values.

== Observational Status ==
Current monitoring of the drought severity index relies on established meteorological and remote sensing datasets, with ongoing efforts to refine measurement techniques and improve spatial and temporal resolution. Data availability varies by region and monitoring infrastructure, influencing the comprehensiveness of drought assessments. Future SIGNAL releases may incorporate enhanced temporal structuring, integration with additional environmental signals, and expanded geographic coverage to support more detailed and dynamic drought monitoring capabilities.

== Related Signals ==
* Burned area (annual)
* Crop heat stress days
* Crop-days under drought stress
* Dryland vegetation cover fraction
* Forest pathogen outbreak severity
* Forest pest infestation severity
* Intensity ratio of cropland irrigation withdrawal to renewable water supply
* Net primary productivity (NPP)

== Key People ==
* Richard R. Heim, Jr.
* Deborah Bathke
* Barrie Bonsal
* Trevor Hadwen
* Kevin Kodama

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== Key Associated People ==
* '''Thomas B. McKee''' — Colorado State University [Source author; High]
* '''Wayne C. Palmer''' — U.S. Department of Commerce, Weather Bureau [Researcher; High]

Inclusion reflects material contribution to the scientific understanding of this damage signal; it does not imply review, endorsement, or affiliation with SIGNAL Earth.
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== Sources ==
* [https://www.drought.gov/data-maps-tools/evaporative-stress-index-esi Evaporative Stress Index (ESI)] — Drought.gov, 2026. [Agency Source; Agency Source; Medium]
* [https://www.sciencedirect.com/science/article/pii/S0034425709001240 Evaporative Stress Index (ESI)] — Remote Sensing of Environment, 2000. DOI: 10.1016/j.rse.2009.04.013. [Paper; Supporting; High]
* [https://agupubs.onlinelibrary.wiley.com/doi/10.1029/WR001i002p00231 Palmer Drought Severity Index (PDSI)] — Water Resources Research, 1965. DOI: 10.1029/WR001i002p00231. [Paper; Supporting; High]
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