Fishermen who ply the waters of the Pacific off the coast of Peru and Ecuador have known for centuries about the El Niño. Every three to seven years during the months of December and January, fish in the coastal waters off of these countries virtually vanish, causing the fishing business to come to a standstill. South American fishermen have given this phenomenon the name El Niño, which is Spanish for "the Boy Child," because it comes about the time of the celebration of the birth of the Christ Child. During an El Niño, the physical relationships between wind, ocean currents, oceanic and atmospheric temperature, and biosphere break down into destructive patterns that are second only to the march of the seasons in their impacts to weather conditions around the world.
sábado, 3 de mayo de 2014
NASA : NASA-CNES Move Forward with Global Water and Ocean Surface Mission
NASA Administrator Charles Bolden, left, and Centre National d'Études Spatiales (CNES) President Jean-Yves Le Gall sign an agreement to move from feasibility studies to implementation of the Surface Water and Ocean Topography (SWOT) mission, Friday, May 2, 2014 at NASA Headquarters in Washington.
NASA and the French space agency Centre National d'Études Spatiales (CNES) have agreed to jointly build, launch, and operate a spacecraft to conduct the first-ever global survey of Earth's surface water and to map ocean surface height with unprecedented detail.
NASA Administrator Charles Bolden and CNES President Jean-Yves Le Gall signed an agreement Friday at NASA Headquarters in Washington to move from feasibility studies to implementation of the Surface Water and Ocean Topography (SWOT) mission. The two agencies began initial joint studies on the mission in 2009 and plan to complete preliminary design activities in 2016, with launch planned in 2020.
"With this mission, NASA builds on a legacy of Earth science research and our strong relationship with CNES to develop new ways to observe and understand our changing climate and water resources," said NASA Administrator Charles Bolden. "The knowledge we'll gain from SWOT will help decision makers better analyze, anticipate, and act to influence events that will affect us and future generations."
SWOT is one of the NASA missions recommended in the National Research Council's 2007 decadal survey of Earth science priorities. The satellite will survey 90 percent of the globe, studying Earth's lakes, rivers, reservoirs and ocean to aid in freshwater management around the world and improve ocean circulation models and weather and climate predictions.
This new agreement covers the entire life cycle of the mission, from spacecraft design and construction through launch, science operations, and eventual decommissioning. NASA will provide the SWOT payload module, the Ka-band Radar Interferometer (KaRIn) instrument, the Microwave Radiometer (MR) with its antenna, a laser retroreflector array, a GPS receiver payload, ground support, and launch services.
CNES will provide the SWOT spacecraft bus, the KaRIn instrument’s Radio Frequency Unit (RFU), the dual frequency Ku/C-band Nadir Altimeter, the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) receiver package, satellite command and control, and data processing infrastructure.
NASA and CNES began collaborating on missions to monitor ocean surface changes in the 1980s. From the TOPEX/Poseidon mission launched in 1992 to the Jason-1 mission launched in 2001 to the Jason-2/Ocean Surface Topography Mission launched in 2008, the collaboration has produced critical information on sea-level rise as well as El Niño causing world-wide impact.
The SWOT mission will use wide swath altimetry technology to produce high-resolution elevation measurements of the ocean surface and the surface of lakes, reservoirs, and wetlands. A more complete inventory of Earth's lakes and the changing amount of water they hold will yield improved assessments of how climate-induced changes can impact freshwater resources worldwide. Only 15 percent of lakes around the world are currently measured from space. SWOT will inventory a majority of medium to large lakes as well as the discharge volumes of rivers.
SWOT will be able to measure the ocean's surface with 10 times the resolution of current technologies. This will allow scientists to study small-scale features that are key components of how heat and carbon are exchanged between the ocean and atmosphere. The higher resolution of SWOT observations also will enable researchers to compute the velocity and energy of ocean circulation. A better understanding of small-scale ocean currents and eddies is also important to impacts on coastal regions such as navigation, erosion and dispersing pollutants.
For more information on the SWOT mission, visit:
NASA and its partners monitor Earth's vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.
For more information about NASA's Earth science activities in 2014, visit:
El Niño: A temperature anomalyThe vast tropical Pacific Ocean receives more sunlight than any other region on Earth. Much of this sunlight is stored in the ocean in the form of heat. Typically, the Pacific trade winds blow from east to west, dragging the warm surface waters westward, where they accumulate into a large, deep pool just east of Indonesia, and northeast of Australia. Meanwhile, the deeper, colder waters in the eastern Pacific are allowed to rise to the surface, creating an east-west temperature gradient along the equator known as the thermocline tilt.
The trade winds tend to lose strength with the onset of springtime in the northern hemisphere. Less water is pushed westward and, consequently, waters in the central and eastern Pacific begin to heat up (usually several degrees Fahrenheit) and the thermocline tilt diminishes. But the trade winds are usually replenished by the Asian summer monsoon, and the delicate balance of the thermocline tilt is again maintained.
Sometimes, and for reasons not fully understood, the trade winds do not replenish, or even reverse direction to blow from west to east. When this happens, the ocean responds in a several ways. Warm surface waters from the large, warm pool east of Indonesia begin to move eastward. Moreover, the natural spring warming in the central Pacific is allowed to continue and also spread eastward through the summer and fall. Beneath the surface, the thermocline along the equator flattens as the warm waters at the surface effectively act as a 300-foot-deep cap preventing the colder, deeper waters from upwelling. As a result, the large central and eastern Pacific regions warm up (over a period of about 6 months) into an El Niño. On average, these waters warm by 3° to 5°F, but in some places the waters can peak at more than 10°F higher than normal (up from temperatures in the low 70s Fahrenheit, to the high 80s).
In the east, as temperatures increase, the water expands, causing sea levels to rise anywhere from inches to as much as a foot. But in the western Pacific, sea level drops as much of the warm surface water flows eastward. During the 1982-83 El Niño, this drop in sea level exposed and destroyed upper layers of coral reefs surrounding many western Pacific islands.
Guillermo Gonzalo Sánchez Achutegui