ATMOSPHERE Part 2. Water Cycle Air pressure- weight of the atmosphere 1.Caused by gravity 2.14.7...
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Transcript of ATMOSPHERE Part 2. Water Cycle Air pressure- weight of the atmosphere 1.Caused by gravity 2.14.7...
ATMOSPHERE Part 2
Water Cycle
Air pressure- weight of the atmosphere
1. Caused by gravity
2. 14.7 lbs/ sq.in at sea level
Barometer- instrument to measure air pressure
Two types:
ANEROID
MERCURY
Clicker
• What causes air pressure?
a) Gravity
b) Inertia
c) Radiation
d) Friction SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
Units of Measurement
1.Millibars- unit on national weather map
2.Inches of Mercury on local weather
1.Conversion- 29.92’’= 1013.25 mb
Latent heat
• Energy absorbed and stored in molecules “hidden”
Homework
• Define/ research:
– Psychrometer
Psychrometer Instrument to
measure humidity
Dry bulb – measures air temp.
Wet bulb – has a water soak wick around the bulb – water evaporates – cools the air
Psychrometer
Dry air - greater evaporation - greater cooling - greater the difference in the 2
temperatures High humidity – no evaporation (saturated
air)- temperatures of the 2
bulbs will be the same or very close
Chart:
HumidityThe more water vapor in the air the
lower the air pressure
Dry air is more dense
H20 is molecularly lighter than N2, O2 and CO2
things that can change air pressure
Specific Humidity ACTUAL
amount of water vapor in the air at a given time and placeUnits - g of
water vapor / Kg of air
Saturated AirAt a steady temperature the
amount of water vapor is at it’s peak (maximum)
Rate of condensation = Rate of evaporation
• Dependent on air temperature• Higher the air temp. - greater
the amount of water vapor in the air
Relative Humidity Comparison of the specific humidity and
the maximum amount of water vapor that the air can hold at a given temperature and pressureUNIT - %
Relative humidity = specific humidity X 100% maximum capacity(saturated)
100% Rel. Hum. – saturated air0% Rel. Hum. – dry air
Clicker
At any given temperature , 1m3 of air can hold 10 g of water vapor. What is the relative humidity at that temperature if 1 m3 of air is holding 9 g of water?
SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
Clicker Dry bulb=22 degrees:
Difference between bulb readings is 5 degrees what is the RH %?
SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
things that can change air pressure
Altitude ( elevation )- As altitude increases; air pressure
decreases
Fewer gas molecules= less pressure
Greatest at sea level or below
Least at the top of mountains
things that can change air pressure
Temperature- warm air becomes less dense than cold air
– Becomes a low pressure
• As temperature increases air pressure decreases
• Cold air will be a high pressure
Dew point: The temperature air must be cooled to in order to reach Saturation.
Any point below water vapor will condense into liquid water.
If dew point falls below freezing point of water we get FROST.
Cloud Formation
Clouds are made of which two states of matter? Water Vapor (gas)Liquid water
Clicker Water needs to condense on a solid
surface there are no solid surfaces in the atmosphere. Using what you know about scattering, what is needed to allow water vapor to condense into a cloud?
a) Lightb) Dustc) UV raysd) Mesosphere
SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
Condensation nuclei
Dust, ice, salt, and other solid particles suspended in the atmosphere.
What else is necessary to form a cloud? *Hypothesis*
Cloud formation: 2 methods Method 1:
Convective cooling○ The lowering of the temperature of a
mass of air due to rising and expanding.○ Most clouds form this way
Temperature changes that occur this way are called Adiabatic temperature changes.
Describe and Diagram
Method 2: Force lifting
Cloud formation requires rising air lifting can come from air forced up
terrain, air being heated and becoming buoyant, frontal systems passing through, etc.
Clicker
How are most clouds formed?a) Force liftingb) Advective coolingc) Convective coolingd) Coalescence
SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
Describe and Diagram: Frontal lifting
Describe and Diagram: Orographic Lifting
(Barrier)
Cloud Identification: the basics
Cumulus
“Puffy” thick high topped clouds Formed by rising moist air that cools
Stratus
“sheet” likeForm when warm moist air lie above a
layer of cool air
Cirrus
“feathery” highest cloudsForm above 6000 m (19685 ft)
Prefix/ Suffix
Alto: Middle
Cirro: Curly
Nimbo/nimbus: Rain
Precipitation
Rain: liquid water in the form of droplets
Freezing Rain: rain that falls when surface temperatures are below freezing.
Snow: precipitation in the form of flakes of crystalline water ice that falls from clouds.
Sleet: form of precipitation consisting of small, translucent balls of ice. Ice pellets are usually smaller than hailstones
Hail: solid precipitation. It consists of balls or irregular lumps of ice, each of which is called a hailstone.
Rain making processes Coalescence
Different size water droplets
Combine to form larger
SupercoolingWater droplets
commonly remain as liquid water and do not freeze, even well below 0 degrees.
Freezing condensation nuclei
Cloud seeding: form of intentional weather modification dispersing substances into the air
that serve as cloud condensation or ice nuclei.