Transcript Lecture 2 (9/10) METR 1111

Lecture 2 (9/16)
METR 1111
Meteorological
Instruments
Thermometers
• Thermometers measure temperature.
• Some types of thermometers:
- liquid-in glass
- bimetallic
- infrared
- thermoelectric
Liquid in Glass Thermometer
• Most common for everyday use (medicine,
cooking, etc.)
• Liquid is either mercury or alcohol
• Difficult to automate – led to development
of other thermometers
Bimetallic Thermometer
• Uses a coil of two different metals attached
to one another
• Different metals expand at different rates
• Used in:
– round outdoor thermometers
– thermostats
• Also difficult to automate
Infrared Thermometer
• Measures the infrared radiation emitted by
an object (night-vision uses it)
• Used to take an instant (not delayed) temp
reading of the air.
• Easily automated
– but other aspects such as ground color can
affect temp readings
Thermoelectric Thermometer
• Most common thermometer for automated
stations
• Advantages: Rugged, reliable, wide
temperature range, inexpensive, and fast
response
• Works by passing a known voltage through
a wire who’s resistance varies as a function
of temperature.
Anemometer
• Used to measure wind speed
• Most common type = cup anemometer
• When the wind is gusty, it overestimates the
avg. wind speed because of momentum
• Must be placed far away from obstacles to
be accurate (Distance = 10x the height of
tallest object)
Wind Vane
• Measures wind direction
• Points parallel with the wind
• Has a “fatter” tail than head so it won’t
point 180º in the wrong direction.
• Easily automated with a rotating sensor
inside the joint with the pole.
Barometer
Aneroid Barometer
• Measures atmospheric pressure
• Works like a weight scale for the air above it
• Aneroid barometer uses gears attached to a sealed
air container that expands or contracts with
decreasing or increasing pressure, respectively.
• Mercury barometer has a bowl with liquid in it
and a tube sealed at the top and open at the bottom
immersed in the liquid. When pressure rises, the
mercury in the tube rises.
Rain Gauge
•
•
Several kinds but tipping bucket rain gauge is the
most useful since it can be automated.
How it works:
- Rain falls into one of two buckets
- When it’s fills up with .01” of rain,
gravity causes it to tip
- Other bucket fills and tips
- Number of tips counted electronically
Other instruments
• Many other instruments are used such as a
hygrometer which measures humidity.
• There are other instruments to collect data
that we will discuss later (radar, satellites,
and rawindondes)
• In METR 3613 “Meteorological
Instruments” you will learn MUCH more
about this subject.
Networks
• Networks are used to collect mass quantities
of weather data. (most are stationary)
• ASOS Network (Automated Surface
Observation System) – nationwide network
for measuring weather conditions every hr.
• Oklahoma Mesonet – unique to Oklahoma,
dense network of weather stations in entire
state, measuring conditions every 15 min.
View of a
Typical
Mesonet
Station
For next time:
• Read Ch 3 in Weather Book (pg 31-45) –
“Why the Wind Blows”
• Do homework 2 and be prepared for the
quiz in class next week.
• Class website:
– weather.ou.edu/~metr1111