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

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A new project of the European Space Agency (ESA) aims to combine data from two different Copernicus Sentinel missions to provide estimates of... read more

Publishing date: 31/07/2020
Central-pivot agricultural fields along the Orange River in South Africa. Image: contains modified Copernicus Sentinel data (2016), processed by ESA.

A grantmaking collective committed to creating and mobilizing labeled datasets that facilitate the development of machine learning applications to address urgent problems has launched a new request for proposals (RFP) for funding. Lacuna Fund, which aims to support as many organizations as possible in using artificial intelligence for social good in low- and middle-income contexts, focuses on agriculture, health and languages. This latest request for proposals will fund labeled agricultural datasets for machine learning in sub-Saharan Africa, whether referenced to Earth observation data or related to other aspects of the crop and animal agricultural system.

Interested organizations headquartered in Africa or having a substantial partnership with organization(s) headquartered in Africa can submit their applications until 3 September 2020. Further details are available... read more

Publishing date: 29/07/2020
Report cover page. Image: UNESCAP.

The United Nations Economic and Social Commission for Asia and the Pacific (ESCAP) has published a policy study concerning the impending climate risk scenarios in South Asia and their intersection with the COVID-19 pandemic. The aim of this report is to facilitate policy actions that could protect communities at risk as well as to lay the foundations of resilient recovery of the most vulnerable in South Asia. 

ESCAP has published two additional reports this year, one on the “Impact and Policy Responses for COVID-19 in Asia and the Pacific”, which presents an initial assessment of the COVID-19 pandemic in Asia and sub-regional... read more

Publishing date: 23/07/2020
Image: UNFPA.

In the latest example of anticipatory humanitarian action, the United Nations released $5.2 million from the Central Emergency Response Fund (CERF) to help communities in Bangladesh prepare themselves ahead of major monsoon floods. The allocation of funds to agencies in the country to prepare to deliver support was triggered by a forecast from the Global Flood Awareness System (GloFAS), which predicted areas having a greater than 50 per cent chance of experiencing a severe flood between 14 and 16 July. Following a second forecast by the Government’s Flood Forecasting & Warning Centre (FFWC) on 11 July, aid workers began distributing the aid.

The swift assistance provided in Bangladesh comes as United Nations Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator Mark Lowcock has agreed to allocate up to $140 million from the UN... read more

Publishing date: 21/07/2020

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