Download Weather Instruments

Weather Instruments
A Thermometer
measures air temperature.
A Thermometer works
because matter expands
when heated. Most
thermometers are closed
glass tubes containing
liquids such as alcohol.
When air around the tube
heats the liquid, the liquid
expands and moves up the
tube. A scale then shows
the actual temperature of
the air.
Thermometers
This also has a Hygrometer,
which measures humidity.
A Barometer
measures air pressure.
An Italian scientist
named Torricelli
built the first
barometer in 1643.
People still use
barometers based
on Torricelli's
design to measure
air pressure.
Barometers
Torricelli’s Barometer
A Psychrometer
measures relative humidity.
Two thermometers are
used in a
Psychrometer. A wet
cloth covers the end of
one of the
thermometers. Water
evaporates from this
cloth, causing the
temperature on that
thermometer to be
different from the other.
A Psychrometer
If the surrounding air is
dry, more moisture
evaporates from the wick,
cooling the wet-bulb
thermometer more so there
is a greater difference
between the temperatures
of the two thermometers.
If the surrounding air
holds as much moisture as
possible - if the
relative humidity is 100%
- there is no difference
between the two
temperatures.
Psychrometers
One of these bulbs
should have a piece
of wet cheesecloth on it.
See the wet “wick”
on one of these bulbs.
An Anemometer
measures wind speed.
The cups catch
the wind, turning
a dial attached
to the
instrument. The
dial shows the
wind speed. Wind
speed can be
estimated
without special
tools by
observation.
Anemometers
A Windsock
is used at airports to indicate wind
direction for takeoffs and landings.
They help the
pilots select
the proper
runway so that
they can take
off and land
into the wind.
Windsocks
A Wind Vane is used to
measure wind direction.
It spins on a
rod and
points in the
direction
from which
the wind
comes.
Wind Vanes
Most airport Wind Vanes have Anemometers also.
A Hygrometer
is an instrument used to
measure the humidity of the air.
A mechanical
Hygrometer
uses human or
horse hairs
which stretch
as they absorb
moisture.
Hygrometers
A Rain Gauge is used to
measure amount of rainfall.
An official Rain
Gauge consists of a
large cylinder with a
funnel and a smaller
measuring tube
inside.
Rain Gauges
A Weather Balloon
measures weather conditions
higher in the atmosphere.
Measures
temperature, air
pressure, wind
speed and
direction
Weather Balloons
Sometimes weather balloons
land in the oddest places!
A Weather Satellite
is able to photograph, track,
and measure the conditions of
large-scale air movements.
A meteorologist then
compiles and
analyzes the data
with the help of
computers.
NOAA weather satellite launched in 2005.
Weather Satellites
Tiros 1 - 1965
NOOA-M measures information about Earth
radiation, sea and land surface temperature,
atmospheric vertical temperature, water vapor,
and ozone in the troposphere and stratosphere.
Weather Satellite
Image
First usuable Tiros 1 image
Weather Prediction
All these instruments are used by
meteorologists to report the current
and predict the future weather.
The End.
Weather Maps
Much information is needed to interpret what is happening
with the atmosphere.
Need to condense this information in a small space
Need to show the geographic characteristics of this
data
Weather maps can both display this data
and summarize the patterns
Station Model
Allows the data to be plotted in a condensed
and usable format
Location of the station on the map.
The name of the location or airport
abbreviation might be given nearby.
Temperature information in
degrees Fahrenheit.
Temp
Dew Point Temperature in
degrees Fahrenheit.
Temp
dewpt
Wind direction
A staff is rotated around the station.
Temp
dewpt
Remember, winds are identified as the direction
FROM which they come. This would be a west
northwest wind or about 290º.
Wind Speed
Attached to the staff are symbols for speed.
Temp
dewpt
The coding for the wind speed symbols
can be generalized as:
half staff about 5 knots
note, it is not on
the end of the
wind direction
staff
full staff about 10 knots
these are additive for the
total amounts
three full staffs=30 knots
65 knots
flag about 50 knots
Current Barometric Pressure
Temp
dewpt
pressure
Barometric Pressure is VERY important!
average barometric pressure at sea
level is 1013.25 mb.
current barometric pressure is
reported to the nearest TENTH
BUT, they don’t want to waste space
average barometric pressure at sea
level is 1013.25 mb.
barometric pressure varies around this value
+ about 30 = 1043
somewhat higher
1013.3
somewhat lower
- about 30 = 983
average barometric pressure at sea
level is 1013.25 mb.
barometric pressure varies around this value
they do not PRINT the beginning
number or numbers
---1013.3
13.3
x
133
they, also, do not PRINT the
decimal point, but report to the
nearest TENTH
From the three numbers, you must
INTERPRET whether the preceding
value is
10
or
9
Which would make the value most
realistic?
add the decimal point
and then consider which, a 10 or a 9
places the value NEAREST to the
average pressure of
1013.25 mb.
What is the pressure?
(1013.3)
084
08.4
1008.4
962
96.2
996.2
281
28.1
1028.1
875
87.5
987.5
322
32.2
1032.2
Not only is the pressure itself
important, but so is the way the
pressure has been changing.
So, more information may be given
and must be coded.
How has the barometer been changing?
Temp
pressure
trend
dewpt
+ it is higher now than in the past
- it is lower now than in the past
How much the pressure has changed
Temp
pressure
trend
change
dewpt
the amount of change in the past three
hours
again, reported in TENTHS without the
What has the pressure been doing?
Shown diagrammatically
Temp
pressure
trend
dewpt
changeshown
Total amount of cloud
Temp
pressure
trend
changeshown
dewpt
graphic depiction of percentage of the sky
covered by clouds
no clouds
about 60%
about 10%
about 75%
about 25%
about 80%
about 40%
completely
overcast
about 50%
sky
obscured
Symbol positions to identify the cloud types
high
clouds
middle
Temp clouds
pressure
trend
changeshown
low
dewpt clouds
Cloud types tell much about the weather
conditions. The cloud types are identified by
symbols, and classed as low, middle, and high
clouds.
How much of the sky is covered by low and
middle cloud cover?
high
clouds
middle
Tempcloudspressure
trend
changeshown
low
dewpt clouds
low or
middle
cloud cover
What amount, in tenths, of the sky is covered by low or
middle clouds. This is a coded number with the
percentage close to the printed number.
What is the present weather?
high
clouds
middle
Tempcloudspressure
wxnow
low
dewpt clouds
trend
changeshown
low or
middle
cloud cover
The current weather is very important.
A detailed set of symbols provides weather
descriptions.
Samples of present weather symbols.
fog
haze
,
thunderstor
m
drizzle
lightning
rain
*slight rain
snow
showers
.
ice or snow
pellets
cloud development
not observed
Combining symbols tells more of the detail.
intermittent
rain, slight at
time of
observation
continuous
rain, slight at
time of
observation
intermittent rain,
moderate at time
of observation
continuous rain,
moderate at time
of observation
intermittent
rain, heavy at
time of
observation
continuous rain,
heavy at time of
observation
100 different symbols provide
details about the PRESENT
WEATHER.
The visibility is especially important for
pilots.
high
clouds
middle
Tempcloudspressure
visibilit wxnow
y dewpt low
trend
changeshown
low or
clouds middle
cloud cover
Visibility is given in miles and fractions
The past weather uses symbols.
high
clouds
middle
Tempcloudspressure
visibilit wxnow
y dewpt low
trend
changeshown
low or
PAST
clouds middle
cloud cover
,
*
Time precipitation began or ended
high
clouds
middle
Tempcloudspressure
visibilit wxnow
y dewpt low
trend
changeshown
low or
PAST
clouds middle
cloud cover
when
Coded for how many hours ago the precipitation began or
ended. Again, the code is close to the number of hours.
Height of cloud base
high
clouds
middle
Tempcloudspressure
trend changeshown
low or
middle PAST when
clouds cloud cover
visibilit wxnow
y dewpt low
base
Coded height of base of clouds.
Important for pilots.
The amount of precipitation
high
clouds
middle
Tempcloudspressure
trend changeshown
low or
middle PAST when
clouds cloud cover
visibilit wxnow
y dewpt low
base
amount
Amount of precipitation is plotted in inches to
the nearest hundredth of an inch.
Decode this station.
237
,,
75
1
65
- 12
6
4
3
36
237
,,
75
1
65
- 12
6
4
3
36
yes
any low clouds?
any middle clouds? yes
any high clouds? yes
amount of low and middle clouds
6
height of cloud base 4
visibility 1 mile
barometric pressure 1023.7 mb
trend in pressure falling
pressure three hours ago 1024.9
how has pressure changed down then steady
present weather continuous slight drizzle
past weather rain
when precipitation began/ended 4
amount of precipitation .36”
temperature 75
dew point 65
wind direction south
wind speed 25 knots
amount of sky cover 80%