NASA’s satellite imagery and model forecasts play an important role in monitoring the performance of crops worldwide and preparing for food shortages. NASA’s view from space helps government agencies forecast food insecurity, like during the drought in Southern Africa in 2018.
An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems, and is recognized by the discoloration in the water from their pigments. Cyanobacteria were mistaken for algae in the past, so cyanobacterial blooms are sometimes also called algal blooms. Blooms which can injure animals or the ecology are called “harmful algal blooms” (HAB), and can lead to fish die-offs, cities cutting off water to residents, or states having to close fisheries. A bloom can block the sunlight from reaching other organisms, deplete oxygen levels in the water, and some algae even secrete toxins into the water.
Snow refers to forms of ice crystals that precipitate from the atmosphere (usually from clouds) and undergo changes on the Earth’s surface. It pertains to frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide or sublimate away. Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime. As snow accumulates into a snowpack, it may blow into drifts. Over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form. Otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater.
Major snow-prone areas include the polar regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture and cold temperatures. In the Southern Hemisphere, snow is confined primarily to mountainous areas, apart from Antarctica.
Snow affects all human activities. Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold.
Video Credit: NASA’s Goddard Space Flight Center/SVS/Trent L. Schindler
When we look into the vastness of space, our home planet stands out in many ways. One of the most crucial is the presence of abundant, accessible freshwater — as a liquid, solid and gas. Water helps make our planet habitable.
The first question NASA researchers studying freshwater on Earth ask is: Where is the water? As it constantly cycles between water vapor, rain and snow, and reservoirs above and below ground, water is tracked by a fleet of NASA satellites. Heat travels with that water, as energy from the Sun drives freshwater’s transformations between vapor, liquid water, and ice. As our planet warms due to greenhouse gases, scientists have a second pressing question: How is climate change affecting the distribution of water?
Music credit: Above It All by Tom Caffey [ASCAP] and Dark Fantasy by Brice Davoli [SACEM]
NASA has a unique and important view of hurricanes around the planet. Satellites and aircraft watch as storms form, travel across the ocean and sometimes, make landfall. After the hurricanes have passed, the satellites and aircraft see the aftermath of hurricanes, from downed forests to mass power loss.
A Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet’s magnetic field. Earth has two such belts and sometimes others may be temporarily created. The discovery of the belts is credited to James Van Allen, and as a result, Earth’s belts are known as the Van Allen belts. Earth’s two main belts extend from an altitude of about 640 to 58,000 km (400 to 36,040 mi) above the surface in which region radiation levels vary. Most of the particles that form the belts are thought to come from solar wind and other particles by cosmic rays. By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.
The belts are located in the inner region of Earth’s magnetosphere. The belts trap energetic electrons and protons. Other nuclei, such as alpha particles, are less prevalent. The belts endanger satellites, which must have their sensitive components protected with adequate shielding if they spend significant time near that zone. In 2013, NASA reported that the Van Allen Probes had discovered a transient, third radiation belt, which was observed for four weeks until it was destroyed by a powerful, interplanetary shock wave from the Sun.
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