Editing Crop-days under drought stress

<!-- SIGNAL_EARTH_INFOBOX_START -->
{| class="wikitable" style="float:right; clear:right; margin:0 0 1em 1em; width:320px;"
|+ SIGNAL Earth Structured Data
|-
! Object type
| Damage Signal
|-
! SIGNAL Earth ID
| DS-00092
|-
! Observable type
| Crop-days under drought stress
|-
! Unit
| crop-days (area of crops multiplied by days under stress)
|-
! Temporal structure
| Periodic
|-
! Monitoring backbone
| —
|}
<!-- SIGNAL_EARTH_INFOBOX_END -->

{{SignalTerm|type=DS|id=DS-00092|label=Crop-days under drought stress}} is an environmental damage signal quantifying the cumulative exposure of agricultural crops to drought conditions over time. This metric integrates the duration and severity of drought stress experienced by crops, providing a measure of potential impact on crop health and productivity. It is relevant for understanding the effects of drought on food security and agricultural sustainability globally.

Drought stress in crops arises when water availability falls below the levels required for optimal growth, leading to physiological strain and reduced yield. Monitoring crop drought stress is essential for assessing agricultural vulnerability to climate variability and guiding adaptive management strategies.

Within the broader context of environmental monitoring, crop-days under drought stress serve as an indicator of receptor response within the human domain, reflecting the intersection of climatic stressors and agricultural systems.

== Geographic / System Context ==
This signal applies globally, encompassing diverse agricultural regions across continents where crops are cultivated under varying climatic conditions. The geographic scope includes rainfed and irrigated croplands, spanning temperate, tropical, and arid zones. Variability in regional climate patterns, soil types, and crop species influences the spatial distribution and intensity of drought stress experienced by crops.

== Monitoring and Measurement ==
Monitoring of crop drought stress involves integrating meteorological data, soil moisture observations, and crop physiological models. Institutions such as the [https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration NOAA], [https://en.wikipedia.org/wiki/National_Aeronautics_and_Space_Administration NASA], and agricultural research organizations employ remote sensing technologies, ground-based sensors, and climate models to estimate drought conditions affecting crops. Measurement conventions typically include indices derived from precipitation deficits, evapotranspiration rates, and soil water availability, combined with phenological crop data to assess stress duration and severity.

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

== Signal Definition ==
The signal 'Crop-days under drought stress' quantifies the cumulative number of days during which crops experience drought conditions sufficient to induce physiological stress. It is measured in crop-days, representing the product of the number of affected crops and the duration of their exposure to drought stress. This signal captures the receptor condition of crops under water deficit, serving as an impact or outcome indicator within agricultural ecosystems.

== Boundary Conditions ==
Boundary inclusions encompass all cropland areas where drought conditions reduce soil moisture below crop-specific stress thresholds, leading to measurable physiological impact. This includes both rainfed and irrigated systems experiencing water deficits. Boundary exclusions involve non-agricultural lands, areas with adequate irrigation mitigating drought effects, and periods outside the crop growing season. Additionally, transient moisture deficits insufficient to cause stress are excluded from the signal definition.

== Aggregation Semantics ==
Geographically, the signal aggregates crop drought stress data across defined agricultural regions, enabling assessment at local, regional, and global scales. Temporally, aggregation occurs over periodic intervals aligned with crop growth stages or calendar periods to capture cumulative stress exposure. Cross-signal aggregation may integrate this signal with related drought severity indices, irrigation withdrawal ratios, and crop yield gap metrics to provide comprehensive assessments of drought impact on agriculture. Aggregation notes emphasize the importance of consistent spatial and temporal resolution to maintain comparability across datasets.

== Observational Status ==
Current monitoring of crop-days under drought stress relies on a combination of remote sensing data and ground observations, though standardized global datasets are still under development. Data availability varies regionally, with ongoing efforts to improve temporal resolution and accuracy. Future SIGNAL releases aim to incorporate enhanced monitoring backbones, refined stress thresholds, and integration with complementary environmental signals to better characterize drought impacts on crops.

== Related Signals ==
* Annual frequency of Crop-days under drought stress threshold exceedance events (declared threshold + averaging window)
* Crop yield gap index
* Drought severity index
* Intensity ratio of cropland irrigation withdrawal to renewable water supply

<!-- SIGNAL_EARTH_PEOPLE_START -->
== Key Associated People ==
* '''Klaus J. Dietz''' (-) [Lead author]
<!-- SIGNAL_EARTH_PEOPLE_END -->

<!-- SIGNAL_EARTH_SOURCES_START -->
== Sources ==
* [https://onlinelibrary.wiley.com/doi/full/10.1111/plb.13304 Drought and crop yield — 2021]
<!-- SIGNAL_EARTH_SOURCES_END -->