Atmospheric Moisture and Precipitation

1
Atmospheric Moisture and Precipitation
2
More Weather

• _______________________- The condition of the
  atmosphere at a certain place and time.
• When talking about weather, you are actually
  describing what is happening in
  the_________________________________.
• Weather is constantly changing.
• Without the_______________________, there would
  be no weather!

3
Factors Of Weather

• These are the most important factors that
  influence weather
• ____________________________________
• ____________________________________
• ____________________________________
• ____________________________________

4
________________________

• Remember the water cycle, the sun
  causes_________________________________, which
  bring moisture to the air.
• The amount of water vapor in the air
  is___________________________________.
• This varies from day to day.
• The amount of water vapor the air can hold
  depends on the temperature of the air.

5
Humidity
_________________________________ compares the
amount of water vapor present in the air to the
maximum amount that the air can hold at that
temperature Expressed as a _____________________
At 100 relative humidity, air is saturated.
6
Humidity

• Relative Humidity changes when
• Atmosphere gains or loses water vapor
• Evaporation
• Temperature changes
• __________________________________? relative
  humidity rises
• __________________________________? relative
  humidity decreases
• Thus, warmer air can hold more water vapor than
  cooler air.

7
_________________________

• Example If you hear a meteorologist say that the
  relative humidity is ________________,that means
  that the air on that day is only holding 50 of
  the water vapor is capable of holding.
• When air is holding all of the moisture it
  possibly can- that means it is said to be
  saturated . Thus, saturated air has 100
  humidity.

8
Relative Humidity

• We are very sensitive to humidity.
  _____________________________________keeps our
  body cool and maintain its current temperature.
• If the air is at 90 relative humidity,
  ____________________________will not evaporate
  into the air. As a result, we feel much hotter
  than the actual temperature when the relative
  humidity is high.
• If the relative humidity is_______________, we
  can feel much cooler than the actual temperature
  because our sweat evaporates easily, cooling the
  body.

9
Relative Humidity

• How relative humidity (RH) is measured?
• Wet- and Dry Bulb__________________________
• It consists of two identical ____________________
  ___thermometers,
• one of which has a wet cotton or linen wick
  around its bulb.
• Evaporating water from the wick absorbs heat
  from the thermometer bulb, causing the
  thermometer reading to drop.
• The difference between dry-bulb and wet-bulb
  temperatures is compared on psychrometric charts.

10
Relative Humidity
How relative humidity (RH) is measured? Wet- and
Dry Bulb ________________
Wet - and Dry Bulb Psychrometer
11
Relative Humidity
How relative humidity (RH) is measured? Wet- and
Dry Bulb Psychrometer Psychrometric Chart.
If the difference between wet and dry bulb is 6º
F and the temperature is 72º F (dry bulb), then
the RH is 54.
12
The Dry Bulb

• Dont let it fool you. It is just a thermometer.
• It measures the _________________temperature.
• Duh!

20C
13
The Wet Bulb

• Has a little wet booty tied to the bottom.
• Gets cool when water evaporates.

12C
Wet Booty
14
Dry-bulb temperature is your air temperature.
The formula for calculating Relative Humidity is
as followed ________ Temperature _ ________Tempe
rature Difference Between Wet and Dry Bulb
Value. Then compare results on the chart First,
look for the Dry Bulb Temperature on the left.
Example 20 C
15
14 C
16
4 C
17
Subtract (the difference) between the dry bulb
and wet bulb
18
20C
14C
20-146
19
18C
16C
18-162
20
Put it all together
20C
8C
20-812
Relative Humidity 11
21
14C
10C
14-104
Relative Humidity 60
22
Humidity

• ______________________ temperature at which air
  with a given humidity will reach saturation when
  cooled without changing its pressure.
• The dew point temperature is the
  ________________________for really measuring the
  amount of moisture in the air. It tells you the
  temperature in which dew will start to form.
  Meaning its saturation point.

23
The Dew Point Chart works the same way
14C
10C
14-104
Dew Point 6C
24
______________________

• Think about the water cycle again, clouds form
  has humid air is cooled to its dew point and
  condense.
• The condensing water vapor forms tiny drops of
  water around dust particles in the atmosphere.
  When millions of these drops form together, a
  cloud forms.

25
________________________

• Yes, there is a classification system to identify
  clouds.
• This system though, helps tell you what kind of
  weather is going to occur.
• In addition this system classifies clouds based
  on shape and altitude.

26
Cloud Types

• Guess What? There are actually different cloud
  types.
• These clouds can help you determine what kind of
  __________________you are going to have.

27
Clouds

• Clouds are divided into categories, in fact 4 of
  them
• ______________________500-18,000 meters
• _____________________above 6,000 meters
• __________________2,000 to 6,000 meters
• ____________________below 2000 meters

28
(No Transcript)
29
(No Transcript)
30
Vertical Clouds

• 500-18,000 meters
• Two Types
• ____________________________________
• ____________________________________

31
__________________________

• These are towering clouds, they spread out to top
  to form an anvil shape.
• Associated with thunderstorms, heavy rain, and
  hail.
• A.K.A ____________________________

32
_______________________

• Dense, _______________________clouds
• Associated with fair weather, but may produce
  precipitation.

33
High Clouds

• Above 6,000 meters
• ___________________________________
• ___________________________________
• ___________________________________

34
_______________________

• These are the ______________________clouds.
• They are made of____________________, not water.
• They are associated with fair weather.
• They are thin wispy clouds. Feather like.

35
Middle Clouds

• 2,000 to 7,000 meters
• _____________________________________
• _____________________________________

36
Mid-Level Clouds ______________" Clouds
Clouds with the prefix "alto" are middle level
clouds that have bases between 2000 and 7000 m
(6500 to 23,000 ft.). Because of their lower
altitudes, they are composed primarily of water
droplets, however, they can also be composed of
ice crystals when temperatures are cold enough.
                                                                          
37
Low Clouds

• Below 2,000 meters or below.
• ____________________________________
• _____________________________________
• _____________________________________

38
_________________________

• Thick layer or dark clouds that block the sun.
• Associated with steady precipitation.

39
__________________

• Thick, clouds that cover the sky.
• Associated with __________________ systems.
• They bring precipitation.
• They act as a blanket- it keeps in_________.
• They are usually low level clouds.

40
__________________________

• Fog is simply __________________clouds right next
  to the ground.
• This caused by air that is cooled to its dew
  point near the ground and condenses.

41
Clouds
Fog is a cloud layer at or close to Earths
surface

• ______________________formed when temperature of
  the air at ground level falls below dew point
• ______________________forms when warm moist air
  moves over a cold surface
• Common over oceans (sea fog)

42
__________________________

• Precipitation is a step in the water cycle. It
  occurs when the clouds cannot hold anymore
  moisture.
• all precipitation occurs because of condensation
• Precipitation occurs in different forms based on
  the temperature of the air.
• _________________________
• _________________________
• __________________________
• ___________________________
• __________________________

43
___________________________________

• The rain shadow effect is when on
  the___________________ side of a
  mountain/mountain chain receives a lot of
  precipitation due to the fact that the air (
  usually rich in moisture) is forced to be lifted
  up the side of the mountain. As the air is
  cooled, it condenses, clouds form and then it
  rains/snows.
• After the air is lifted over the peak of the
  mountain, the air has to go down. As the air
  goes down, it is warmed, and the clouds break and
  usually ___________precipitation.
• Thus, on the _____________________side of the
  mountain, it is very dry due to little
  precipitation.

44
Orografic effects in orogens
45
____________________________

• Hail forms when__________________of water in
  layers around a small nucleus of ice.
• Hail forms in_______________________. They grow
  larger as they are tossed up and down by rising
  and falling air currents in a storm.

46
_________________________!!

• Coffeyville,___________________, in 1970. The
  largest hailstone ever documented, it weighs 0.75
  kilograms (1.67 pounds), and spans 14.4
  centimeters (5.67 inches).

47
_____________________
Sleet forms when ________________passes through a
layer of warm air, melts and then
________________________near the ground. It
requires a deep layer of cold air near the
ground.
48
How Does Sleet Form?
49
Freezing Rain
50
_________________________
It causes a glaze on objects. Cause for
most____________________. As snow falls from the
clouds, it melts ____________________________and
there is a shallow layer of cold air at the
surface and causes it to__________________________
____.
51
______________
_____________________is a function of
subfreezing temperatures through out the
atmosphere and the surface. It does not
_____________________at all as it falls from the
upper atmosphere.
52
LAKE-EFFECT SNOW
53
Overview of the Lake-Effect Process

• Occurs to the____________________ of the Great
  Lakes during the cool season
• Polar/arctic air travels across a lake, picks up
  heat and moisture, and is destabilized.

54
Lake-Effect-type Phenomena in Other Regions

• Lake-effect (_____________________)
• Lake-effect (Finger Lakes, NY)
• Bay-effect (Chesapeake, Delaware, Massachusetts
  Bays)
• Ocean-effect (Gulf Stream, Sea of Japan)

55
LAKE-EFFECT

• Occurs during the unstable season when mean lake
  temperatures exceed mean land temperaturesaka,
  the __________________is warmer than the land.
• Mean annual snowfall exceeds 100 inches in the
  snowbelts to the lee of the lakes, and exceeds
  200 inches in the Tug Hill Plateau in New York,
  to the lee of Lake Ontario and on the Keweenaw
  Peninsula of northern Michigan, to the lee of
  Lake Superior. Occurs heavily in__________________
  __________, on lee of_________________________.

• 
  from Eichenlaub
  (1979)

56
Basic Concepts of Formation
The warm water provides thermalenergy and
moisture to theoverlying cold air
rememberthat thermal energy transportis from
warm to cold.
57
Basic Concepts of Formation
The rising air condenses to formprecipitation,
and snow fallsdownwind of the shore line.
Thegreater the air-water temperaturecontrast,
the heavier the snowfall
58
Review On How Lake Effect Happens.
Cold Outbreak Frigid air flows over warm water
and is warmed from below. Moisture evaporates
into the air.
Heavy Snow Warmer more moist air rises downwind
of the lakes and often forms heavy snow squalls.
59
Effect of Orography
60
Snow ___________________
Sometimes lake-effect snow clouds develop enough
up and down motion to create "thundersnow" - a
snow storm with _________________________________
_______________.
61
__________________________

• _____________________ measure air temperature.
  Thermometers work 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 that shows
  the temperature is on, or attached to, the tube.

62
__________________________

• A ___________________measures air pressure. An
  Italian scientist named Torricelli built the
  first barometer in 1643. People still use mercury
  barometers based on Torricelli's design to
  measure air pressure.

63
Glass tube from which the air has been removed is
inserted into a dish of mercury. The air pressing
down on the mercury in the dish forces some of
the mercury up into the glass tube. At the
Earth's surface, air pressure pushes the mercury
about 30 inches up into the tube - give or take
close to a couple of inches.
64
_________________________

• An instrument used for measuring the water vapor
  content of the atmosphere.
• A psychrometer measures relative humidity

65
Sling Psychrometer

• It consists of two glass thermometers containing
  a liquid, usually mercury. One thermometer
  measures the air temperature while the other one
  measures the wet-bulb temperatures.
• After the wick is dipped in distilled water, a
  weather observer whirls the sling psychrometer
  around, using the handle. As the instrument is
  whirled, water evaporates from the wick on the
  wet-bulb thermometer and cools the thermometer.

66
_________________________.

• The lowest temperature that can be obtained by
  evaporating water into the air at constant
  pressure. The name comes from the technique of
  putting a wet cloth over the bulb of a mercury
  thermometer and then blowing air over the cloth
  until the water evaporates. Since evaporation
  takes up heat, the thermometer will cool to a
  lower temperature than a thermometer with a dry
  bulb at the same time and place. Wet bulb
  temperatures can be used along with the dry bulb
  temperature to calculate dew point or relative
  humidity

67
Sling Psychrometer
68
__________________________

• Is an instrument that measures wind speed.

69
__________________________

• Measures Wind Direction!!!

70
Combined-Wind Vane and Anemometer

• Most weather stations combine these two
  instruments.

71
(No Transcript)
72
_______________________

• The most common rain gauge used today by official
  forecasters and airports was invented over
  _________________________ years ago.
• it consists of a large cylinder with a funnel and
  a smaller measuring tube inside of it. The
  official rain gauge has a 50 centimeter high
  cylinder with a 20 centimeter in diameter funnel
  that collects water into a measuring tube that
  has exactly one-tenth the cross sectional area of
  the top of the funnel.

73
(No Transcript)
74
_________________________measure the upper air!!!

• Weather balloons carry instrument packages called
  _______________________________high into the
  atmosphere that gather essential upper-air data
  needed to forecast the weather. These instruments
  are launched twice a day at ____________________
  sites around the world. Temperature,
  ______________________and air pressure are
  measured at various altitudes and transmitted via
  radio waves to a receiving station. Radio
  navigation supplies wind speed and direction at
  each altitude.

75
Up and Away Balloon lifts a milk carton-sized
box of instruments 20 miles into the atmosphere.
The Descent The balloon pops and the radiosonde
floats back to earth by a parachute.
Radiosonde Instruments in the box measure three
things _________________, _________________ and
_________________