Drought

Lake Chad has shrunk dramatically over the last four decades due to a decrease in rainfall and an increase in the amount of water used for irrigation projects. Its surface area was 25 000 sq km in the early 1960s, compared with 1350 sq km in 2001. Image acquired 19 December 2007 by the MERIS (Medium Resolution Imaging Spectrometer) instrument aboard ESA’s Envisat satellite. Image: ESA, CC BY-SA 3.0 IGO.

Definition

Drought may be considered in general terms a consequence of a reduction over an extended period of time in the amount of precipitation that is received, usually over a season or more in length. It is a temporary aberration, unlike aridity, which is a permanent feature of the climate. Seasonal aridity (i.e., a well-defined dry season) also needs to be distinguished from drought. It should be noted that drought is a normal, recurrent feature of climate, and it occurs in virtually all climatic regimes (UNDDR).

Facts and figures

Droughts are often predictable: periods of unusual dryness are normal in all weather systems. Advance warning is possible (WHO).

By 2025, 1.8 billion people will experience absolute water scarcity, and 2/3 of the world will be living under water stressed conditions (UNCCD).

Drought can be defined according to meteorological, agricultural, hydrological and socio-economic criteria.

  • Meteorological, when precipitation departs from the long-term normal
  • Agricultural, when there is insufficient soil moisture to meet the needs of a particular crop at a particular time. Agricultural drought is typically evident after meteorological drought but before a hydrological drought
  • Hydrological, when deficiencies occur in surface and subsurface water supplies
  • Socio-economic, when human activities are affected by reduced precipitation and related water availability. This form of drought associates human activities with elements of meteorological, agricultural, and hydrological drought (FAO).

Further information

National Droight Mitigation Center, University of Nebraska, Education section
NASA Earth Observatory, Drought Facts
WMO Handbook of Drought Indicators and Indices

Related content on the Knowledge Portal

Data Source

JAXA Climate Rainfall Watch
JAXA Climate Rainfall Watch. Image: JAXA
Publishing institution: Japan Aerospace Exploration Agency (JAXA)
Early Warning eXplorer (EWX - RCMRD)
Screenshot of the RCMRD Early Warning eXplorer (EWX).
Publishing institution: Regional Centre for Mapping of Resources for Development (RCMRD)
The RCMRD Early Warning eXplorer (EWX) is a web-based application for exploration of geospatial data related to drought monitoring and famine early warning, customized for application in the African countries. It includes datasets such as rainfall at 5km, maximum temperature, rainfall forecasts and NDVI. The EWX enables scientists, analysts, and policymakers to view diverse data sets side-by-side in the same spatial bounding box, while also stepping through sequences of multiple time-series data sets. The EWX also allows users to view different statistics for user-selected regions by administrative zone, crop zone, hydrologic zones, grazing areas, or country.The RCMRD Early Warning eXplorer (EWX) is a web-based application for exploration of geospatial data related to drought monitoring and famine early warning, customized for application in the African countries. It includes datasets such as rainfall at 5km, maximum temperature, rainfall forecasts and NDVI. The EWX enables scientists...
Global Drought Observatory (JRC)
Screenshot of GDO
Publishing institution: Joint Research Centre (JRC)
The Global Drought Observatory provides drought-relevant information such as maps of indicators derived from different data sources (e.g. precipitation measurements, satellite measurements, modeled soil moisture content). It uses the Combined Drought Indicator (CDI) for agricultural/ecosystem drought, which is based on three indicators: Precipitation Anomalies (SPI), Soil Moisture Anomalies and Fraction of Absorbed Photosynthetically Active Radiation (fAPAR). Exposure layers used by GDO are gridded population data (based on the Global Human Settlement Layer at 1 km resolution for 2015); agricultural lands (based on the Global Agricultural Lands in the Year 2000 dataset, a result of a combination of MODIS and SPOT-VEGETATION data with agricultural inventories); gridded livestock of the world (at a spatial resolution of 3 min x 3 min latitude-longitude for 2005); and baseline water stress (a indicator of relative water demand for 2010). The Risk of Drought Impacts for Agriculture...
Digital Earth Africa
Publishing institution: Geoscience Australia
The Digital Earth Africa (DE Africa) Map is a website for map-based access to spatial information. It’s is still being developed by Data61 CSIRO in collaboration with Geoscience Australia. DE Africa is leveraging international Earth Observation (EO) data and science to produce new information and services that benefit African countries. Through translating data into ready-to-use insights, more informed decisions about soil and coastal erosion, agriculture, deforestation, desertification, water quality and changes to human settlements can be made. The data is organized in data-cubes and will be fully available by 2020.

Actualités

New JAXA website provides hourly global measurements of precipitation
JAXA Climate Rainfall Watch. Image: JAXA.

The Japan Aerospace Exploration Agency (JAXA) has released the JAXA Climate Rainfall Watch website to monitor extreme weather and climate over the world. The website provides hourly global measurements of precipitation as well as forecasts about heavy rainfall and drought in different temporal scales (daily, pentad, weekly, 10-days and monthly). The satellite-based global rainfall maps produce highly accurate measurements that can help better understand the changing climate, improve forecasts of extreme weather events, such as floods and droughts, minimize their damage and strengthen early warning systems.

The Climate Rainfall Watch website monitors heavy rainfall and drought in near-real-time and collects and stores data from previous months. The website calculates rainfall in percentile: heavy rain is indicated by large percentile value and displayed in dark pink color. The website also monitors drought using the Standardized Precipitation Index (SPI),... read more

Publishing date: 15/04/2020
Regional workshop addresses role of Earth observation in multi-hazard disaster risk assessment and Sendai framework monitoring
Image: UNOOSA.

In order for South Asian Association for Regional Cooperation (SAARC) Member States to be able to incorporate the routine use of space technology-based solutions, there is a need to increase awareness, build national capacity and develop solutions that are customized to their needs. The regional workshop and capacity-building programme on the "Role of Earth Observation in Multi-Hazard Disaster Risk Assessment and Monitoring Targets of the Sendai Framework" is the second regional event in South Asia under the umbrella of the SAARC Disaster Management Center and the United Nations Office for Outer Space Affairs (UNOOSA), through its UN-SPIDER programme. The event took place in collaboration with the International Water Management Institute (IWMI), Sri Lanka, the Space Applications Centre of the Indian Space Research Organisation (ISRO) and the Centre for Space Science and Technology Education in Asia Pacific (CSSTEAP). It was built on the outcome of the first regional workshop and... read more

Publishing date: 12/12/2019
Regional Support Offices mentioned:
International Water Management Institute (IWMI)
New NASA sensor to support drought and wildfire prediction

Major disasters such as droughts and wildfires are driven by the dryness of vegetation. To enhance the monitoring of plant water stress, NASA launched and installed a new sensor on the International Space Station. ECOSTRESS (ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station) allows identifying loss of water in leaves- even before they show visible signs of trouble.

The image to the left shows a product derived from ECOSTRESS data, indicating that the forest fires during the 2019 Amazon dry season were concentrated in water-stressed areas, which are not visible on optical imagery. “To the naked eye, the fires appear randomly distributed throughout the forest,” said Josh Fisher, ECOSTRESS science lead at NASA’s Jet Propulsion Laboratory.

Plants regulate their... read more

Publishing date: 14/11/2019

Événement

Introductory Webinar: Satellite Remote Sensing for Agricultural Applications
Satellite Remote Sensing for Agricultural Applications logo. Image: NASA

This four-part introductory webinar will focus on data products, data access, and case-studies demonstrating how remote sensing data can be used for decision-making among the agriculture and food security communities.

This training will address how to use remote sensing data for agriculture monitoring, specifically drought and crop monitoring. The webinar will also provide end-users the ability to evaluate which regions of the world agricultural productivity is above or below long-term trends. This informs decisions pertaining to market stability and humanitarian relief.

By the end of this training, attendees will be able to:
  • Identify which satellites and sensors can be used for agricultural applications
  • Understand the limitations of remote sensing and modeled data for agriculture and food security
  • Acquire specific remote sensing data products that are appropriate for their work
  • Apply remote sensing techniques to crop monitoring,... read more
New Sensor Highlight: ECOSTRESS
Image: NASA.

This webinar will focus on a NASA instrument that was launched and installed on the International Space Station in summer 2018. Designed to study terrestrial ecosystems and plant water stress from the ISS, ECOSTRESS can also be used to better understand crop health, volcanoes, urban heat, wildland fires, coastal systems, and much more. 

The primary science and applications mission of ECOSTRESS is to address three critical questions around vegetation health and agriculture:

  1. How is the terrestrial biosphere responding to changes in water availability?
  2. How do changes in diurnal vegetation water stress impact the global carbon cycle?
  3. Can agricultural vulnerability be reduced through advanced monitoring of agricultural water consumptive use and improved drought estimation?
... read more

Advisory Support

Tunisia - Technical Advisory Mission

At the request of, and in coordination with the National Civil Protection Office of Tunisia, UN-SPIDER is conducting a Technical Advisory Mission to Tunisia from 4 to 6 March 2020 to identify the needs of the country to fully take advantage of space-based information for disaster management. In order to discuss the use of space-based information for risk and disaster management to subsequently make recommendations on improvements, the expert team meets with key disaster management authorities in the country.

The mission is conducted with the support of experts from the Algerian Space Agency (ASAL); the Romanian Space Agency (ROSA); the United Nations Economic Commission for Africa (UNECA); the National Observatory of Athens (NOA); and an expert on the Copernicus Emergency Management Service. The mission team is also benefiting from the support of the Chief of Space Applications of the United Nations Office for Outer Space Affairs.

As part of the mission, the team of experts will visit several institutions including the National Office of Civil Protection; the Directorate General for Forests of the Ministry of Agriculture; the Faculty of Sciences of Tunis, University of Tunis El Manar; the National Agronomic Institute of Tunisia; the National Institute of Meteorology; as well as at the Ministry of Local Affairs and Environment. Meetings will also be conducted with representatives of the National Cartographic and Remote Sensing Centre of Tunisia and other organizations. In addition, the TAM team will meet the United Nations Country Team in Tunisia, which supports disaster management efforts in the country.

During the TAM, a workshop with over 20 participants from nine institutions will take place in order to present the UN-SPIDER programme to Tunisian counterparts involved in disaster management, and encourage inter-institutional cooperation and sharing of geospatial information among them.

UN-SPIDER aims at ensuring all countries have the capacity to use all types of space-based information to support risk and disaster management efforts. To make sure that all interested stakeholders can benefit from this information in the most effective way possible, UN-SPIDER provides Technical Advisory Support to Member States through missions such as this one.

The Algerian Space Agency (ASAL), the Romanian Space Agency (ROSA) and the National Observatory of Athens (NOA) are UN-SPIDER Regional Support Office.

On request of the Tunisian Government and immediately after the technical advisory mission, UN-SPIDER conducted a three-day hands-on training on the use of Sentinel-1 radar data for flood mapping. In order to further strengthen the capacity of Tunisia to use space technologies for disaster management, UN-SPIDER will continue to encourage the participation of Tunisian institutions in its conferences and expert meetings. In addition, together with its regional and international partners, UN-SPIDER will provide training on forest fire mapping in the medium term. 

Mission dates: 04/03/2020 to 06/03/2020
Regional Support Offices mentioned:
Algeria Regional Support Office, Greece Regional Support Office, Romania Regional Support Office

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