E

Earth’s core / Core of the Earth

Innermost layer of the Earth´s structure, believed to consist of two sub-layers: inner core (solid) and outer core (composed of liquid) of mostly metallic iron and nickel.

Earthquake

Sudden movement of the earth, caused by a strain release inside it. They often happen along tectonic plates boundaries.

Eccentricity

The extent to which an elliptical orbit departs from a circular one.

Ecological drought

Drought conditions that result in adverse effects on the biota, which is the plant and animal life of a region.

El Niño

Anomalous increase of sea surface temperature off the west coast of South America, over the eastern and central equatorial Pacific, that occurs at irregular intervals, usually between two and seven years. Generally, it produces heavy rainfall over coastal areas of Chile, Peru and Ecuador and it develops during the first months of the year and decays during the following year. Currently, El Niño is considered part of a larger-scale phenomenon born in the ocean-atmospheric interactions across the equatorial Pacific, that is the Southern Oscillation, coining the expression “El Niño-Southern Oscillation –ENSO-“.

El Niño Southern Oscillation (ENSO)

Expression that recognizes the linkage between El Niño and the Southern Oscillation. So, it is the warming of surface and sub-surface waters in the eastern tropical Pacific Ocean, due to a change (reversal) in the east-to-west pressure patterns in the equatorial Pacific.

Electromagnetic spectrum

Ordered sequence of electromagnetic radiations (propagation of energy through space or material media by wave disturbances in electric and magnetic field), from the shortest cosmic rays, through gamma and x rays, ultraviolet, visible and infrared radiation, to microwave and every other radio wavelengths.

Ensemble forecast

Forecast in which a computer model runs many times, changing slightly the initial data –pressure, temperature and other meteorological variables-, to predict conditions over the same forecast period.

Equinox

Either of the two points of intersection of the Sun’s annual path (ecliptic) with the plane of the Earth’s equator (celestial equator), heading northward or southward. This happens on or about March 21st and on or about September 22nd, vernal and autumnal equinox respectively (these dates are reversed in the Southern Hemisphere). Popularly, it is when the sun passes above the equator.

Erosion

Movement of soil or rock from a place to another, by action of the sea, running water, moving ice, wind or precipitation. When human actions and activities increase natural erosion, it is called accelerated erosion.

Evaporation

Physical process by which a liquid substance changes to the gaseous state, emitting water vapor at a temperature below its boiling point. Amount of water evaporated.

Evaporation rate

Quantity of actual evaporation per unit area, per unit time.

Evapotraspiration

Process by which a transfer of water to the atmosphere occurs, by virtue of evaporation from the Earth’s surface (open waters, ice surfaces and bare soil) and transpiration of plant surfaces. It also designates the total amount of water transferred from the Earth to the atmosphere.

Exosphere

Outermost portion or layer of the atmosphere, whose lower boundary locates at 300-600 miles approximately (500-1000 km) above the Earth’s surface.

Extra-tropical cyclone

Cyclone has moved poleward from tropical waters. The term implies that the main energy source of the cyclone is no longer the release of latent heat of condensation, but the baroclinic processes (contrast between warm and cold masses). Although being extra-tropical, these cyclones can retain winds of hurricane or tropical storm force.

Eye

Region of clear or nearly clear skies, light winds and subsiding or descending air, at the core of a mature hurricane or tropical cyclone.

Eyewall

Ring of cumulonimbus (thunderstorm clouds) that surrounds the eye of a tropical cyclone, bearing the storm’s most intense winds. To be called so, the clouds must occupy at least 180 degrees of arc in radar depictions.