METEOROLOGY AND CLIMATE
UNIT #7
WHAT YOU NEED TO
KNOW FOR THE TEST!
Cloud Formation Vocabulary
• Absolute humidity – actual amount of water in the air
at that temperature
• Condensation nuclei – air particles of dust or salt from
the ocean
• Convection – transfer of heat energy by currents
• Density – mass per unit volume of a substance
• Dew point – temperature at which condensation occurs
• Sublimation – change of phase from solid to gas
(or gas to solid) with no intermediate liquid phase
• Troposphere – lowest layer of the atmosphere where all
weather occurs
Weather instruments measure weather conditions. One of the
most important conditions is air pressure, which is measured
with a barometer, shown below. See the other commonly used
weather instruments:
Rising air pressure =
fair weather
Falling air pressure =
foul weather
•Thermometer measures temperature.
•Anemometer measures wind speed.
•Rain gauge measures the amount of rain.
•Hygrometer measures humidity.
•Wind vane shows wind direction.
•Snow gauge measures the amount of snow.
Change of Phases – Heat Energy
ESRT pg. 1
If something is getting warmer (increased temperature), heat energy is gained.
If something is getting cooler (decreased temperature), heat energy is released.
HEAT TRANSFER
How is heat transferred in the atmosphere?
Radiation, Conduction, Convection
HEAT TRANSFER BY CONVECTION
Local breezes are generated by unequal heating of
Earth’s surface due to local conditions
Warm, less dense air is pushed upward,
while more dense, cool air descends,
creating a SEA BREEZE during the day
(sea to land)
Cool, more dense air descends, while
warm, less dense air is pushed upward,
creating a LAND BREEZE at night
(land to sea)
SPECIFIC HEAT
The quantity of heat, measured in joules, needed to raise
the temperature of 1 gram of a substance 1o C.
The higher the specific heat of a substance, the greater amount of heat needed to
raise its temperature. If a substance requires more heat to “heat up”, it will take
longer for it to heat up, which means it will also take longer for it to “cool down”.
ESRT pg. 14
Temperature Scale
ESRT pg. 14
REMEMBER:The dry bulb is the air temperature.
The wet bulb is swung in the air as water
evaporates, removing heat from the bulb
of the thermometer, which causes the
temperature to be lower (cooler).
*The closer the air temperature and
dewpoint temperature, the higher the
relative humidity (precipitation!).
PRACTICE QUESTIONS
ADIABATICISM
(OROGRAPHIC EFFECT)
Dry lapse
rate: 10o
Moist lapse
rate: 6o
--Dry lapse rate occurs between the land surface and the base of cloud
(dew point)—as air ascends, altitude increases/temperature decreases.
--Moist lapse rate occurs from dew point to the top of the cloud—as
altitude increases/ temperature continues to decrease.
--From the mountain peak air descends back down to the land surface—
as altitude decreases, temperature increases, and the dry lapse rate
continues again down to the base of the mountain at Earth’s surface.
STATION MODELS
ESRT pg. 13
Altitude and Air Pressure
Higher up in elevation, there is
less air above so the air pressure
decreases.
At the surface of the Earth the air pressure is greater
because there is more air above you!
Density and Air Pressure
More molecules, packed
tightly together
The lower
the air
density,
the
lower the
air pressure!
Higher weight per volume
The higher
the air
density,
the
higher the
air pressure!
Fewer molecules, spread out.
Lower weight per volume
Temperature and Air
Pressure
Cold air is more dense!
As air
temperature
decreases,
air pressure
increases!
High
Pressure!
H
Low
Pressure!
As air
temperature
increases,
air pressure
decreases!
L
Warm air is less dense!
The wind blows because air has weight!
1) Cold air
weighs
more than
warm air, so
the pressure
of cold air
is
greater.
Low
Pressure!
High
Pressure!
H
2) When
the sun
warms
the air,
it
expands,
gets lighter,
and rises.
3) Cooler, heavier
air blows to
where the
warmer and
lighter air was.
L
CORIOLIS EFFECT
The Coriolis Effect is the apparent curvature of global
winds, ocean currents, and everything else that moves
freely across the Earth’s surface. The Coriolis Effect
is due to the rotation of the Earth on its axis.
If not for the Earth’s rotation, global winds would blow
in straight north-south lines. What actually happens is
that global winds blow diagonally. The Coriolis Effect
influences wind direction around the world in this
way: in the Northern Hemisphere it curves winds to
the right; in the Southern Hemisphere it curves them
left. The exception is with low pressure systems. In
these systems there is a balance between the Coriolis
Effect, and the pressure gradient force and the winds
flow in reverse.
To sum up ‘what is the Coriolis Effect’-- it is an
important meteorological force that is used to predict
the directional path of storms.
http://www.youtube.com/watch?v=mcPs_OdQOYU
AIR MOVEMENT
Coriolis Effect is the
deflection of air near
Earth’s surface caused
by Earth’s rotation.
N. Hemisphere 
S. Hemisphere 
A wind is named for the direction from which it comes!
Westerly Wind
PRESSURE GRADIENT FORCE
The change in pressure measured across a given distance is called a
“pressure gradient”. The higher the force, the faster the wind speed.
As an air parcel moves from high pressure to low pressure because of the
pressure gradient force, it is deflected by the Coriolis force to the right in the
Northern Hemisphere.
On which side of the hill is the greatest wind speed, and why?...
The wind blows fastest on the left side where the isolines are
closest together. This is where the greatest change is.
Weather Fronts - A weather front is a boundary
separating two masses of air of different densities.
Symbol
Front
Warm Front -- A warm front is
defined as the transition zone
where a warm air mass is replacing
a cold air mass.
Cold Front -- A cold front is defined
as the leading edge of a cooler mass
of air, replacing (at ground level) a
warmer mass of air.
Stationary Front -- is a boundary
between two different air masses,
neither of which is strong enough to
replace the other.
PRECIPITATION occurs right at the cold front
and ahead of the warm front
The COLD air mass
front is steep and the
WARM air mass front
is more gentle.
*NOTE: that the cold,
heavier air mass, is
associated with HIGH
PRESSURE, is
typically below the
lighter, less dense
warm air.
YOU NTK THIS!!!
SYNOPTIC WEATHER MAP
WET moisture belt = warm, converging air rising
DRY moisture belt = cool, divergent air sinking
CLIMATE PATTERNS
CLIMATE is the average temperature and amount of precipitation for an area
over a long time (annually). Compared to the climate at location A, the climate
at location B would most likely be WARM (sinking, compressed air) and DRY (low
humidity, away from moisture source)—desert region.
FACTORS INFLUENCING CLIMATE
• Latitude
• Altitude
• Mountain ranges
• Oceans/lakes
• Ocean currents
• Landmass location
• Arid air – dry
• Humid air – moist
Climate types:
• *Arctic – very cold, dry
• Polar – cold, moist
• Temperate – varied
temperatures (4 seasons)
• *Tropical – warm, humid
*(little seasonal change)