Gathering Weather Datapg. 79

Surface Data Instruments

thermometer- filled with mercury or alcohol; expands when heated

barometer- measures air pressure; mercury and vacuum chamber

anemometer-measures wind speed; cupped arms that rotate as the wind blows

hygrometer- measures relative humidity; uses a wet and dry bulb

ceilometer-measures the height of cloud layers and sky coverage

Automated surface observing system

meteorologists must have data from all these instruments at the same time

National Weather Service has 1700 sites that collect data at regular intervals

collected by the ASOS

Upper Level Data

weather we experience is the result of changes high in the troposphere (30000 m)

use balloon- borne package of sensors called a radiosonde

measure temp, air pressure, and humidity

constantly sent by radio signal to a ground station

tracks movement of radiosonde and then data is plotted on charts

very expensive

Weather Radarradar-radio detecting and ranging

transmitter generates electromagnetic waves --> waves leave through the antenna

waves programmed to ignore small cloud droplets and bounce off large raindrops

waves are scattered (called echoes) and picked up by other antenna

waves are amplified and distance is calculated

radar system rotates in a circle to collect data in range of about 400 km

Doppler Radar

doppler effect- when frequency of a wave changes as it moves toward or away from an observer

used to plot speed of raindrops as they move toward and away a radar station

provides good estimation of wind speed esp during severe thunderstorms and tornados

http://www.youtube.com/watch?v=z0EaoilzgGE

Weather Satellites

satellites are used to take photos of earth

track clouds and not necessarily precipitation

coupled with weather radar

Infrared Imagery

weather stations use visible light and invisible radiation

infrared imagery detects differences in thermal energy

allows meteorologists to determine temp of a cloud and then the type of cloud

used to detect the intensity of a thunderstorm