Transcript Coriolis Effect

~25,000-56,000 feet
Average height - 36,000 feet
-56.5 C
Troposphere

Troposphere is thickest over the equator and
lowest over the poles.
Generally…
 Tropopause is higher and colder in a warm air
mass.
 Tropopause is lower and warmer in a cold air
mass.
Coriolis Effect



Air tends to flow from high
to low pressure
Due to the rotation of the
Earth, the air flow appears
to be deflected when
observed from the surface
of the Earth
Air flow is deflected to the
right in the northern
hemisphere. (to the left in the
southern hemisphere)
http://www.wiley.com/college/strahler/047148053
3/animations/ch07_animations/animation2.html


Coriolis effect greatest at poles and zero at the equator
Therefore, deflection is greatest at higher latitudes
~ 25 degrees North latitude
~ 60 degrees North latitude
PRESSURE GRADIENT
Geostrophic Winds

As the airflow is
deflected due to
coriolis effect the
resulting wind begins
to become
perpendicular to the
pressure gradient force
(parallel to the isobars).


Geostrophic winds run parallel to the isobars.
They are the result of an equilibrium between
pressure gradient force and coriolis effect.
Buys Ballot Law
• Stand with the wind at your back.
• Stick out your left arm.
• Your fingers will point to the center of the low
pressure area
Flow due to Surface Friction


Surface friction at low
altitudes tends to
diminish coriolis effect
and cause the winds to
flow slightly inwards
towards Lows and
outwards from Highs
Friction also slows the
wind flow
Veering and Backing


When the wind direction changes clockwise we
say it is veering
When the wind direction changes counterclockwise we say it is backing
Backing
Veering
Wind due to Surface Friction


Winds back in direction and slow in speed close
to the surface
Winds veer in direction and increase in speed as
altitude increases
Aloft (>2000 feet)
Surface
Surface Friction
•The wind speed and direction change depends on the
friction coefficient of the surface
• Winds may only back by 10 degrees over water and
as much as 40 degrees over rough terrain
Winds 270 at 50 knots
> 2000 feet AGL
Winds 260 at 40 knots
Winds 245 at 30 knots
Winds 230 at 25 knots
Water
Flat land
Rugged terrain
Convection Cells

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Imagine a non-rotating Earth
The equator will be heated by
solar radiation causing the
warm air to rise
The air over the poles will cool
causing it to subside
This will form a circulation flow
as seen in the diagram
HIGH
LOW
Convection Cells

In our real, rotating
world the Coriolis Force
and other factors cause
the single cell to break
up into three cells.
http://www.gerhards.net/astro/wolken_200705_full.html
Prevailing Winds
Jet Streams

High velocity channels of wind in the uppernorthern corners of the Hadley and Ferrel Cells.
(More on Jet streams later)
LAPSE RATES

STANDARD LAPSE RATE
1.98OC / 1000 feet

DRY ADIABATIC LAPSE RATE
3OC / 1000 feet

SATURATED ADIABATIC LAPSE RATE
Average 1.5OC / 1000 feet
SATURATED RANGE ACTUALLY 1.1OC TO 2.8OC
Altitude
Latent heat of
vaporization
released
Saturated Adiabatic Lapse Rate
1.5 C / 1000 feet
Dry Adiabatic Lapse Rate
3 C / 1000 feet
Temperature
The actual lapse rate at any given
time is called the Environmental
Lapse Rate (ELR)
LAPSE
RATES
Absolute Instability
ELR
3.5 C / 1000 feet
SALR
Altitude
Air pocket
continues to rise
DALR
Temperature
Conditional Instability
Altitude
ELR
2.5 C / 1000 feet
Air pocket
continues to rise
SALR
(Clouds will form
if air is saturated)
DALR
(No clouds if
air is not saturated)
Air pocket will
not continue to rise
Temperature
Absolute Stability
ELR
1 C / 1000 feet
Altitude
SALR
(No clouds form)
DALR
(No clouds form
Air pocket will
not continue to rise
Temperature
Absolute Stability (Inversion)
Altitude
ELR
3.5 C / 1000 feet
Air pocket will
not continue to rise
Temperature
Inversion
1oC/1,000
16 oC
2oC/1,000
12 oC
3oC/1,000
10 oC
10.5 oC
10.5 oC
17 oC
14 oC
11 oC
12 oC
18 oC
16 oC
14 oC
15 oC
19 oC
18 oC
18 oC
17 oC
18 oC
20 oC 21 oC
20 oC
21 oC
19.5 oC
19.5 oC
20 oC
21 oC
16 oC
Water vapour and tiny water droplets at any altitude stay there
17 oC
18 oC
19 oC
20 oC
1oC/1,000 lapse rate
Shallow lapse rate
8 oC
11 oC
16 oC/16oC
14 oC
17 oC/17oC
oC
18 oC/18oC
17
20 oC
21 oC/18oC
3oC/1,000 lapse rate
Steep lapse rate
water vapour goes up with rising air pockets
Steep lapse rate in the air mass
Shallow lapse rate in the air mass
Cumulus type cloud
Stratus type cloud
Precipitation in showers
Precipitation is steady and lighter
Thunderstorms
Fog
Good visibility
Poor visibility
Bumpy conditions
Smooth conditions
UNSTABLE
STABLE