Transcript Gathering Weather Data

Gathering Weather Data
pg. 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 Radar
radar-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