Transcript 1AER200-MET1

Meteorology
Subject:
Faculty:
ADVANCED AERONAUTICS
Brian CARLICK
Subject Code: AER 200
Date:
January 11, 2006
– COMPOSITION AND STRUCTURE
OF THE ATMOSPHERE
– PRESSURE
– STANDARD ATMOSPHERE
–
TEMPERATURE
–
MOISTURE
–
STABILITY
–
WINDS
–
CLOUDS
Atmosphere Composition
and Properties
10 0 %
Atmosphere has weight
– 14.7 psi @ sea level or 1013.2 mb
– Half of it is below 18,000 feet
– No well defined upper surface but
satellite drag data indicates
some air at 1,000 miles
– Gases each contribute to
Oxygen
21%
atmospheric pressure
Water/Other 1%
– Water vapour usually less
Nitrogen
78%
than 1% but can be 3.5%
90%
80%
70%
60%
50%
40%
30%
20%
10 %
0%
Properties /
Structure of the
Atmosphere
• Water Vapor is essential for weather
– found in lower levels
– responsible for clouds and precipitation
• H2O vapour (10) is lighter than O2 (16) or N2 (14)
• H2O content varies hour to hour, day to
day, by season and by latitude
• Water content changes depending on
temp & pressure
Properties /
Structure of the
Atmosphere
• Air is a fluid
• Mobility, expansion & compression
• Lifting agents can be Frontal, Thermal,
Orographic, Mechanical
• Rising air is subjected to reducing
pressure and expands and cools
As air expands
(rising) pressure
decreases and
temperature
decreases
15 oC
20 oC
25 oC
As air compresses
(sinks) pressure
increases and
temperature
increases
Vertical Structure
THERMOSPHERE
IONOSPHERE
3000 ° C @700km
MESOPAUSE
MESOSPHERE
STRATOPAUSE
STRATOSPHERE
TROPOPAUSE
TROPOSPHERE
SEA LEVEL
KM
120
110
100
Vertical Structure
-108 °C
90
275,000 feet
80
Temperature distribution
70
60
-2.5 °C
165,000 feet
50
40
30
20
36,089 feet
10
0
-110
-100
-90
-80
-70
-60
-56.5 °C
-50
-40
-30
-20
-10
0
10
20
30
40
50
EXOSPHERE
Starts 500 to 800 km up
IONOSPHERE
80km to 400km
-108 °C
MESOPAUSE
-2.5 °C
STRATOPAUSE
6 to 30 miles
-56.5 °C
TROPOPAUSE
°C
Humidity and Dew point
• Warm air can hold more moisture.
• The water vapor a volume of air can hold is governed
by its temperature.
• Air is said to be saturated when it contains the
maximum amount of water it can hold at that
temperature.
• Dew point - the temperature to which unsaturated air
must be cooled to become saturated.
• Relative Humidity - the ratio of actual water vapor
present in the air to the amount which that volume of
air would hold if saturated.
• When air is heated, without adding water, the relative
humidity decreases.
• The Thermosphere is important because it
contains properties of mobility, and it has a
capacity for expansion and contraction.
– Allows movement under it, ie. lows and highs
• The Thermosphere also contains the
Ionosphere, which can affect radio waves.
– Jet Streams are found at the top of the
troposphere, much lower than the thermosphere.
They are higher at the equator and lower at the
poles. They descend in winter and rise in
summer.
Pressure:
• Is important for determining altitude
• Distribution determines winds (mobility).
• Is Force exerted by the air at that altitude
Area
• Station pressure: is the actual atmospheric
pressure at the elevation of the observing
station.
• MSL: is used to compare the pressures of
stations with different elevations.
Pressure, Density &
Altimeter settings
Eg.
34000 feet
7.40
29.92
Actual pressure
Pressure setting
18000 feet
28.92
29.92
1000 feet
500 feet
14.90
29.92
14.90
29.92
29.42
29.92
Sea level
29.92
29.92
Defining the Standard Atmosphere
•
•
•
•
•
•
29.92”Hg (1013.2 mb) @ sea level
15° C @ sea level
1.98° C per 1,000 feet
1”Hg = 1,000 feet (varies with height)
1 mb = 30 feet
Air is presumed perfectly dry for standard
Low Pressure
•
•
•
•
•
•
•
•
Low or Cyclone is rising air
Bad weather, poor visibility
Stratus clouds, light winds
Movement:
– Summer: 500 miles / day
– Winter: 700 miles / day
Winds:
– Above 3000agl: parallel to isobars
– Below 3000agl: INTO the low
Consistent day and night temperatures
Low pressure is by comparison to surrounding areas
Counterclockwise rotation in Northern hemisphere
Buys Ballot’s 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 !!!
High Pressure
•
•
•
•
•
•
•
•
•
Anti-cyclone is descending air, compression occurs
Clockwise circulation in Northern hemisphere
Highs fill in Lows
Surface winds blow outwards in a slow spiral
Clear skies predominate
Higher day temperatures, lower night temperatures
Good visibility
Cumulus type clouds
Breezy
Wind
• The heating of the earth’s surface is
responsible for circulation. The sun heats
the earth which then radiates the heat,
heating the adjacent air at the surface.
• Upper winds flow parallel to isobars, with
wind speed determined by the spacing.
• Surface winds are slower due to surface
friction, and will blow in or out depending
on the surrounding pressure.
PRESSURE GRADIENT
HIGH
LOW
2nd low
TROUGH
COL
RIDGE
1000 +/WIND
Gusts and Squalls
• Gusts: rapid, irregular fluctuation in
velocity and direction. Peak 5 kt higher
than 2 minute average
• Squalls: longer in duration. 15 kt higher
than mean speed and peak for 2 minutes
Land Breeze
Wind
cooling land
water
Sea Breeze
Wind
warming land
water
FUNNEL EFFECT
Katabatic (night)
Chinooks
Anabatic (day)
Valley Breezes
KATABATIC WIND
ANABATIC WIND
WIND vs TURBULENCE
STRATUS
CUMULUS
Clouds
• Stable vs. Unstable (Horizontal/Vertical)
• 2 main types - Stratus vs. Cumulus
• Heights of clouds give 4 families
- High
- Middle
- Low
- Vertical development
CLOUD CLASSIFICATIONS
GROUP
TYPE
TOPS 40,000
HIGH
CLOUDS
TOPS 20,000
MIDDLE
CLOUDS
TOPS 6,500
LOW
CLOUDS
CLOUDS OF
VERTICAL
DEVELOPMENT
BASE 20,000
BASE 6,500
BASE SURFACE
BASE 1,600 UP
CIRRUS
CI
CIRROSTRATUS
CS
CIRROCUMULUS
CC
ALTOSTRATUS
AS
ALTOCUMULUS
AC
ALTOCUMULUS
CASTELLANUS
ACC
STRATUS
ST
NIMBO STRATUS
NS
STRATOCUMULUS
SC
STRATUS FRACTUS
SF
CUMULUS FRACTUS
CF
CUMULUS
CU
TOWERING
CUMULUS
TCU
CUMULONIMBUS
CB