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).

Related content

SAM Satellite

Landsat 4 was launched on July 16, 1982. The Landsat 4 spacecraft was significantly different than that of the previous Landsats, and Landsat 4 did not carry the RBV instrument.
In addition to the Multispectral Scanner System (MSS) instrument, Landsat 4 (and Landsat 5) carried a sensor with improved spectral and spatial resolutioni.e., the new satellites could see a wider (and more scientifically-tailored) portion of the electromagnetic spectrum and could see the ground in greater detail. This new instrument was known as the Thematic Mapper (TM).
Landsat 4 was kept in... read more

Launch date:
16/07/1982

Landsat 3 was launched on March 5, 1978, three years after Landsat 2.
The Landsat program’s technical and scientific success together with political and economic pressures lead to the decision to commercialize an operational Landsat. To this end, responsibility was slated to shift from NASA (a research and development agency) to the National Oceanic and Atmospheric Administration (NOAA), the agency charged with operating the weather satellites. This was done via Presidential Directive/NSC-54 signed on Nov. 16, 1979 which assigned NOAA “management responsibility for civil operational land remote sensing activites.” (However, operational management was not transfered from NASA to NOAA until 1983).
Landsat 3 carried the same sensors as its predecessor: the Return Beam Vidicon (... read more

Launch date:
05/03/1978

Landsat 2 was launched into space onboard a Delta 2910 rocket from Vandenberg Air Force Base, California on January 22, 1975, two and a half years after Landsat 1. Originally named ERTS-B (Earth Resource Technology Satellite B), the spacecraft was renamed Landsat 2 prior to launch. The second Landsat was still considered an experimental project and was operated by NASA.
Landsat 2 carried the same sensors as its predecessor: the Return Beam Vidicon (RBV) and the Multispectral Scanner System (MSS).
On February 25, 1982 after seven years of service, Landsat 2 was removed from operations due to yaw control problems; it was offically decommissioned on July 27, 1983.

Instruments:
Return Beam Vidicon (RBV)
Multispectral Scanner (MSS)
 

Launch date:
22/01/1975

Landsat 1 was launched on July 23, 1972; at that time the satellite was known as the Earth Resources Technology Satellite (ERTS). It was the first Earth-observing satellite to be launched with the express intent to study and monitor our planet’s landmasses. To perform the monitoring, Landsat 1 carried two instruments: a camera system built by the Radio Corporation of America (RCA) called the Return Beam Vidicon (RBV), and the Multispectral Scanner (MSS) built by the Hughes Aircraft Company. The RBV was supposed to be the prime instrument, but the MSS data were found to be superior. In addition, the RBV instrument was the source of an electrical transient that caused the satellite to briefly lose altitude control, according to the Landsat 1 Program Manager, Stan Weiland.
To help understand the... read more

Launch date:
23/07/1972

News

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-... read more

Publishing date: 12/12/2019
Regional Support Offices mentioned:

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... read more

Publishing date: 14/11/2019

Data Source

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.
Publishing institution: Joint Research Center, European Commission (JRC)
GIS Malawi is a webmapper which provides various vector and raster layers covering a broad range of topics including natural hazards.

Event

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... read more

UN-SPIDER Training Activity

International Training Programme on Space-Based Technologies for Disaster Risk Assessment | Date of training: 05/09/2019 to 09/09/2019

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