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.


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).

Related content on the Knowledge Portal

SAM Satellite

NOAA-19, designated NOAA-N' (NOAA-N Prime) prior to launch, is the last of the United States National Oceanic and Atmospheric Administration's POES series of weather satellites. NOAA-19 was launched on February 6, 2009.

On November 4, 2008, NASA announced that the satellite had arrived at Vandenberg aboard a C-5 Galaxy military transport aircraft. Installation of the payload fairing took place January 27, 2009; second stage propellant was loaded on January 31.

Several attempts were made to conduct the launch. The first attempt was scrubbed after a failure was detected in a launch pad gaseous nitrogen pressurization system. The second attempt was scrubbed after the failure of a payload fairing air conditioning compressor, which is also part of the ground support equipment at the launch pad.

The satellite was successfully launched at about 2:22 a.m. PST. February 6, 2009 aboard a Delta II flying in the 7320 configuration from Vandenberg Air Force Base.

... read more

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The GeoEye-1 satellite sensor was successfully launched on September 6, 2008. The satellite, which was launched at Vanderberg Air Force Base, California, provides a resolution of 0.46 meters.

GeoEye-1 is capable of acquiring image data at 0.46 meter panchromatic (B&W) and 1.84 meter multispectral resolution. It also features a revisit time of less than three days, as well as the ability to locate an object within just three meters of its physical location.
The GeoEye-1 satellite sensor features the most sophisticated technology ever used in a commercial remote sensing system. This sensor is optimized for large projects, as it can produce over 350,000 square kilometers of pan-sharpened multispectral satellite imagery every day.
GeoEye-1 has been flying at an altitude of about 681 kilometers and is capable of producing imagery with a ground sampling distance of 46 centimeters, meaning it can detect objects of that diameter or greater.
During late summer of... read more

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RapidEye is a full end-to-end commercial Earth Observation system comprising a constellation of five minisatellites, a dedicated SCC (Spacecraft Control Center), a data downlink ground station service, and a full ground segment designed to plan, acquire and process up to 5 million km2 of imagery every day to generate unique land information products.
The system is owned and operated by BlackBridge. MDA (MacDonald, Dettwiler and Associates Ltd) was the mission prime contractor and was responsible for the delivery of the space and ground segments, launch of the constellation, and on-orbit commissioning and camera calibration. The two major subcontractors to MDA were SSTL (Surrey Satellite Technology Ltd.) for the spacecraft bus, SCC and spacecraft AIT (Assembly, Integration and Test) services, as well as Jena Optronik GmbH (JOP) who provided the 5-band multispectral imager (RGB, red edge, and near IR bands).
The RapidEye constellation represents a major milestone... read more

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Cartosat-2 is an advanced remote sensing satellite with a single panchromatic camera (PAN) capable of providing scene-specific spot imageries for cartographic applications. The camera is designed to provide imageries with better than one meter spatial resolution and a swath of 10 km. The satellite will have high agility with capability to steer along and across the track up to + 45 degrees. It will be placed in a sun-synchronous polar orbit at an altitude of 630 km. It will have a revisit period of four days. The re-visit can be improved to one day with suitable orbit manoeuvres.

Several new technologies like two mirror on axis single camera, Carbon Fabric Reinforced Plastic based electro optic structure, lightweight, large size mirrors, JPEG like data compression, advanced solid state recorder, high-torque reaction wheels and high performance star sensors are being employed in Cartosat-2.

Instrument: PAN (Panchromatic Camera)
- high resolution... read more

Launch date:

The WorldView-1 offers a high-capacity, panchromatic imaging system which features 0.46m resolution imagery.

Operating at an altitude of 496 kilometers, WorldView-1 satellite has an average revisit time of 1.7 days and is capable of collecting up to 750,000 square kilometers (290,000 square miles) per day of half-meter imagery. The satellite is also equipped with state-of-the-art geo-location capabilities and exhibits stunning agility with rapid targeting and efficient in-track stereo collection.

WorldView-1 satellite sensor was successfully launched from Vandenberg Air Force Base, California, U.S.A., at 11:35 Hrs Pacific Daylight Time (PDT) on September 18th, 2007.

Instrument: WV60 (WorldView-60 camera)
- spectral range 0.45 - 0.90 µm
- swath width: 17.6km at nadir
- pushbroom imager

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TerraSAR-X is a German Earth-observation satellite. Its primary payload is an X-band radar sensor with a range of different modes of operation, allowing it to record images with different swath widths, resolutions and polarisations. TerraSAR-X thus offers space-based observation capabilities that were previously unavailable. The objective of the mission is to provide value-added SAR (Synthetic Aperture Radar) data in the X-band, for research and development purposes as well as scientific and commercial applications.
The successful launch of TerraSAR-X on 15 June 2007 at 08:14 local time from the Russian Baikonur Cosmodrome in Kazakhstan marked the start of a campaign to map the Earth at an unprecedented level of accuracy. The aim is to create new, high-quality radar images of the Earth’s surface.

Instrument: SAR (Synthetic Aperture Radar)
- the sensor operates in the X-band and in 3 different modes (Spotlight, Stripmap, ScanSAR)

Launch date:

METOP (Meteorological Operational) is Europe's first polar-orbiting operational meteorological satellite. It is the European contribution to the Initial Joint Polar System (IJPS), a co-operative agreement between Eumetsat and the US National Oceanic and Atmospheric Administration (NOAA) to provide data for climate and environmental monitoring and improved weather forecasting. The first MetOp-A satellite was launched in 2006, with the other two following at five-year intervals. In total, the programmes will be operational for at least 14 years.
Launched in October 2006, MetOp-A, the first satellite in the series of three, replaced one of two satellite services operated by NOAA and is Europe’s first polar-orbiting satellite dedicated to operational meteorology. Once operational in orbit, responsibilities for the meteorological satellite services have been shared between the USA and Europe.
The MetOp satellites are designed to work in conjunction with the NOAA satellite... read more

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KOMPSAT-2 (Korea Multi-Purpose Satellite-2), also referred to as Arirang-2 by South Korea, has been developed by KARI (Korea Aerospace Research Institute) to continue the observation program of the KOMPSAT-1 mission.

The main mission objectives of the KOMPSAT-2 system are to provide a surveillance of large scale disasters and its countermeasure, acquisition of independent high resolution images for GIS (Geographic Information Systems), composition of printed maps and digitized maps for domestic and overseas territories, balanced development of Korean territories, survey of natural resources, and continuation of satellite earth observation after KOMPSAT-1.

Instrument: MSC (Multispectral Camera)
- resolution: 1m panchromatic, 4m multispectral
- swath width: approx. 15km


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ALOS (Advanced Land Observation Satellite) has been decommissioned. ALOS was successfully launched on January 24, 2006 from the Tanegashima Space Center.

ALOS was one of the world's largest earth observation satellites whose function is to collect global and high resolution land observation data. ALOS data was made available at conditions similar to those of ERS and Envisat missions, namely for scientific 'Category-1' use as well as commercial applications.

The ALOS (renamed "Daichi") satellite sensor had three remote-sensing instruments: the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and for digital elevation models (DEMs). The Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) for precise land coverage observation, and the Phased Array type L-band Synthetic Aperture Radar (PALSAR) for day-and-night and all-weather land observation and enabled precise land coverage... read more

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Today, weather satellites scan the whole Earth, meaning not a single tropical storm or severe weather system goes undetected. The early detection and warnings they provide have saved thousands of lives.
Meteosat data is of unique value to nowcasting of high impact weather in support of safety of life and property.
It has been shown to improve weather forecasts and severe weather warnings which, in turn helps limit damage to property and benefits industry e.g. transport, agriculture and energy.
Meteosat-9 provides a backup service to Meteosat-11 Full Earth scanning and a gap filling service to Meteosat-10 Rapid Scanning.

GERB (Geostationary Earth Radiation Budget)
MSG Comms (Communications Package for MSG)
SEVIRI (Spinning Enhanced Visible and Infra-Red Imager)

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