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

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)

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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

Launch date:

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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NOAA-18, known before launch as NOAA-N, is a weather forecasting satellite run by NOAA. NOAA-N (18) was launched on May 20, 2005, into a sun-synchronous orbit at an altitude of 854 km above the Earth, with an orbital period of 102 minutes. It hosts the AMSU-A, MHS, AVHRR, Space Environment Monitor SEM/2 instrument and High Resolution Infrared Radiation Sounder (HIRS) instruments, as well as the SBUV/2 ozone-monitoring instrument. It is the first NOAA POES satellite to use MHS in place of AMSU-B.

APT transmission frequency is 137.9125 MHz (NOAA-18 changed frequencies with NOAA-19 on June 23, 2009).

AMSU-A (Advanced Microwave Sounding Unit - A)
AVHRR/3 (Advanced Very High Resolution Radiometer / 3)
HIRS/4 (High-resolution Infra Red Sounder / 4)
MHS (Microwave Humidity Sounding)
S&RSAT (Search & Rescue Satellite-Aided Tracking System)
SBUV/2 (Solar Backscatter Ultraviolet / 2)
DCS/2 (Data Collection... read more

Launch date:

Cartosat-1 satellite sensor was built by ISRO (Indian Space Research Organization) which is mainly intended for cartographic applications was launched by the PSLV on May 5, 2005 at Sriharikota, India.
Prior to launch, ISRO renamed the IRS-P5 spacecraft to CartoSat-1, to describe more aptly the application spectrum of its observation data. In this mission, the high resolution of the data (2.5 m GSD) is being traded at the expense of multispectral capability and smaller area coverage, with a swath width of 30 km. The data products are intended to be used in DTM (Digital Terrain Model)/DEM (Digital Elevation Model) generation in such applications as cadastral mapping and updating, land use as well as other GIS applications.

Instrument: PAN (Panchromatic Camera)
- high resolution optical imager
- max swath: 30km

Launch date:

IRS-P6 is an Earth observation mission within the IRS (Indian Remote-Sensing Satellite) series of ISRO (Indian Space Research Organization), Bangalore, India. The overall objectives of the IRS-P6 mission (ResourceSat-1) are to provide continued remote sensing data services on an operational basis for integrated land and water resources management. IRS-P6 is the continuation of the IRS-1C/1D missions with considerably enhanced capabilities.

Prior to launch, ISRO renamed the IRS-P6 spacecraft to ResourceSat-1, to describe more aptly the application spectrum of its observation data.

LISS-4 (Linear Imaging Self-Scanning Sensor-4)
LISS-3 (Linear Imaging Self-Scanning Sensor-3)
AWiFS (Advanced Wide Field Sensor)

Launch date:

On 26 September 2003 Nigeria launched its $13 million national satellite NigeriaSat-1 in Plesetsk, Russia under a seven-nation constellation being handled by a Russian firm, Cosmos. Nigeriasat-1 is a low earth orbit micro satellite for disaster monitoring looking spacecraft, 5-year target design life-span orbit 700km. The launching of the National Satellite, which started development in November 2001, had been postponed from July 2003 because the Russian Space Agency had to launch a military satellite during that period. NigeriaSat-1 is one of five satellites which will make up a network called the Disaster Monitoring Constellation. The other partners in the international consortium are UK, China, Algeria, Turkey, Thailand and Vietnam. Each satellite belongs to one country, but they will share information with each other when disaster monitoring is needed. The Disaster Monitoring Constellation satellites, which cost less than $10 million each, are built by a British-based company,... read more

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