HOPKINS GLOSSARY OF WEATHER TERMS E

electrical thermomete

• Any type of thermal sensor (thermometer) instrument with a sensor element having electrical properties that are a function of temperature. Two electrical-type thermometers are the thermocouple, which uses a thermally dependent generated voltage potential or thermistor, which employs thermally dependent electrical resistance.

elevation

• Vertical distance of a point on or affixed to the surface of the ground, measured from mean sea level; contrast with altitude (1), which is a vertical distance of a point not necessarily affixed to the ground.

elevation angle (also called altitude angle)

• The angle (in degrees) between the horizon and a point above the local horizon in the celestial sphere, measured along the great circle that passes through both the zenith and the point in question.

escape velocity

• The vertical speed needed for an object to escape the planetary or stellar gravitational field; the escape velocity influences the composition of the earth's outer atmosphere, especially in the exosphere.

exosphere

• The region near the outer edge of the earth's outer atmosphere where particles escape to outer space. The lower boundary is typically found at altitudes exceeding 700 km above the earth's surface.