Transcript WEATHER

WEATHER
Weather vs. Climate
 Weather – the atmospheric conditions
over a relatively short period of time
Climate – the weather in some location
averaged over a long period of time

Weather Measurements
What weather phenomena do we need
to measure? What instruments do we
use to measure them?
Coe Lake Weather Measurements
Tradition & Electronic
Temperature
 Atmospheric Pressure
 Rainfall
 Relative Humidity
 Wind Direction
 Wind Speed

CLOUD TYPE REVIEW

These cloud types should be familiar
to you. Write down the website if you
need to go back to revisit them.
http://asd-www.larc.nasa.gov/SCOOL/cldchart.html



“Cirrus” or “Cirro” – high (base above 6000 m)
“Alto” – mid (base 2000 m-6000 m)
No prefix – low clouds
Temperature


Two scales – Celsius & Fahrenheit
http://www.sciencemadesimple.com/conversions.html
–
–
–
–
–
–
–
Boiling Point of Water
Average Body Temperature
Hot Summer Day
Average Room Temperature
Cool Fall Day
Warm Winter Day
Freezing point of Water


212 °F
98.6 °F
85 °F
68 °F
55 °F
40 °F
32 °F
You must know ABT & ART in °C
You must know the BP & FP of Water in °C
100 °C
37 °C
29.4 °C
20 °C
12.8 °C
4.4 °C
0 °C
Thermometers

We use a variety of thermometers at
Coe Lake
– All measurements will be done in Metric!
– Digital thermometers
– Thermometers with various scale
markings that make it challenging for
students to read
– “What’s Hot & What’s Not?”
– “Weatherwise”
Thermometers
ATMOSPHERIC PRESSURE



Atmospheric pressure (or air pressure) is the weight
of Earth's atmosphere on the surface at a given
location and is generated by the downward force of
Earth's gravity.
Atmospheric pressure depends on the amount of air
above the location where the measurement is
taken, consequently the pressure drops as you go
higher.
Also known as Barometric Pressure because it is
measured with a barometer.
Barometric Pressure
Unit Craziness!

National Weather Service:
– inches of Mercury (inHg)
– mm of Mercury (mmHg)
– hectoPascals (hPa)

A Pascal is the metric unit for air pressure and
100,920 Pa is equal to 1009.20 hPa
– millibars (mb) (same as hPa)
Average Atmospheric
Pressure at Sea Level

In Weatherspeak:
– 29.9 inHg
– 1013.25 hPa
– 1013.25 mb

In Chemspeak:
–
–
–
–
101.325 kPa
760 mmHg
1.00 atm
14.7 psi
Barometers
Rainfall (Snowfall)



Rainfall impacts all of us, from the lack of
rain during times of drought to the dangers
of flash floods when we receive too much
rain too fast.
It is the depth of water reaching the
ground, typically in inches or millimeters.
Rainfall rate
– Light = 0.10 inches of rain per hour
– Moderate = 0.10 to 0.30 inches of rain per hour
– Heavy = over 0.30 inches of rain per hour
Rainfall



An inch of rain is exactly that, water
that is one inch deep.
One inch of rainfall equals 4.7 gallons
of water per square yard or 22,650
gallons of water per acre! Wow!
Measured with a Rain Gauge.
Rain Gauges
Relative Humidity




The amount of moisture in the air relative to
how much moisture the air can hold.
Temperature dependent.
Higher temperatures – the air can hold
more moisture. (Think about hot, humid
summer days…)
Lower temperatures – the air holds less
moisture. (The relative humidity might be
the same as a hot summer day, but less
moisture will be in the air.)
Relative Humidity



Humidity is measured with a
hygrometer.
Relative humidity is measured with a
Sling Psychrometer.
Humidity measurements can be used
to calculate dew point and heat index.
Relative Humidity Chart
Heat Index
Measuring Humidity
Wind Measurement



Wind is the natural motion of the air roughly
parallel to the Earth's surface.
It is caused by the unequal heating and
cooling of the Earth and atmosphere by the
sun, which produces differences in air
pressure.
Air tends to flow from areas of higher
pressure to lower pressure.
Wind Measurement
Wind occurs at all scales.






Global winds (trade winds)
Upper level winds (jet streams)
Synoptic winds (resulting from the pressure
differences of surface air masses)
Local (mesoscale) winds (such as gust fronts)
Winds that develop because of geographical
features (like sea breezes).
Winds also occur on a much smaller scale, for
example dust devils or tornadoes.
Wind Measurement
Wind measurements are taken at a fixed
location and measure two parameters:
 Wind Speed – mph, kph, knots
 Wind Direction – cardinal directions;
always naming the wind for the
direction from which it comes
– EX: a SE wind comes from the southeast
Wind Speed – Anemometer
Wind Direction – Wind Vane
What do you need to know?

What are the various weather phenomena and
– What are the definitions?
– What tool is used to measure it?
– What metric unit is used to measure it?
Match the name of the cloud to its altitude using
the correct prefixes (alto & cirro)
What are the metric and English (F)
temperatures for the bp & mp of water, body
temperature & room temperature?
What is the difference between weather and
climate?
