Transcript Cadet Phase I & II Aerospace Dimensions Introduction to

Cadet Phase I & II
Aerospace Dimensions
Air Environment (Module 3)

Session 1:
Chapter 1 ‘Air Circulation’
 Chapter 2 ‘Weather Elements’


Session 2:
Chapter 3 ‘Moisture and Clouds’
 Chapter 4 ‘Weather Systems and Changes’

(ONLY for all Cadets that have not yet passed corresponding AE test, and Cadet Mentors)
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
1
Air Circulation

Radiation - a method of Heat Transfer

This is the ONLY way heat can travel in a vacuum, and
is therefore how the Sun heats the Earth
 About 65% of the sun’s energy gets past the clouds
 15% is absorbed by the atmosphere, the remaining 50% is
absorbed at the Earth’s surface

Heat and Pressure differences in the atmosphere,
caused by Solar Heating are what causes weather
 Heating and Cooling of the atmosphere also
evaporates/condenses water vapor, causing clouds,
rain, snow, and hail
 Temperature and Pressure Changes also affect air
density, which directly affects LIFT
(remember Module 1?)
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
2
Air Circulation

Rotation and Revolution
The Earth Revolves around the sun once every 365
days (approx.)
 The Earth also Rotates, tilted at an angle of 23.5°
 Revolution and Rotation together cause the seasons, and

different weather patterns at different latitudes
 Tilted towards the sun = long day
 Tilted away from the sun = short day
 Sun tracking along equator = day/night of equal length
– Autumnal Equinox: Equal length Day/Night (Fall - Sept 22/23)
– Vernal Equinox: Equal length Day/Night (Spring - Mar 21/22)
– Summer Solstice: Longest Day (June 21/22)
– Winter Solstice: Shortest Day (Dec 21/22)
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
3
Air Circulation


Coriolis effect: Since the Earth is rotating Counter-Clockwise,
anything travelling from North to South will be deflected WEST of
the intended destination, if the fact that the earth is moving under
them, is not accounted for
Circulation


Uneven heating (e.g. equator and poles) causes pressure
differences, which result in movement of air
Air is heated at the equator,
rises, then heads north or south,
eventually cooling, and then
much of it returns to the equator
 This creates the ‘Trade Winds’,
between 0° and 30° Lat. and an
area of calm (rising) wind
at the equator, called the
‘Doldrums’
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
4
Air Circulation


Other predictable Wind patterns include:
 Prevailing Westerlies, are cooling air moving towards the
poles between 30° and 60° latitude
 Above 60° latitude cooling and descending polar air forms
Polar Easterlies
VERY large Temperature and Pressure differences, high up
(in the Troposphere) cause special high speed winds called
Jet Streams
 These travel in a band around the earth at between 100
and 300 MPH
 There are 4 jet streams, one of
which is over the United States
 Ours is at 30,000 to 35,000 ft, and
travels West to East, dipping South
over the Mid West (but it moves!)
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
5
Air Circulation

Important Terms (Quiz):
 Autumnal
 Coriolis
Equinox
Effect
 Jet Stream
 Radiation
 Revolution (of Earth
around Sun)
 Equal length Day/Night
(Fall - Sept 22/23)
 Vernal
Equinox
 Equal length Day/Night
(Spring - March 21/22)
 Summer
 How long does it
Solstice
 Longest Day (June 21/22)
 Winter
Solstice
 Shortest Day (Dec 21/22)
Dr. R.A. Bartholomew
-
take?
 Rotation
(of Earth)
 What angle is the
earth’s axis tilted at?
Civil Air Patrol, New Jersey Wing
6
Weather Elements

Wind
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‘A body of air in motion’
Wind is defined by its Direction and Speed
 e.g. Easterly (FROM the East) at 20 knots
 1 knot = 1.1 MPH
The Beaufort Scale (0 to 12) defined different wind strengths,
by describing visible effects for different Wind Speeds
Wind can make the air feel colder than it is - this effect is
called Wind Chill
 The wind is removing the warm air from around your body, and
speeding heat loss
 A chart can be used to determine the wind chill
 Flying into wind increases lift, flying with the wind increases
speed, flying cross-wind pushes you off course.
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
7
Weather Elements


Microburst
 A very strong, very fast moving downdraft, often from a
thunderstorm, resulting in extreme turbulence
Temperature



Temperature is the result of Heating, and is measured in degrees
Fahrenheit (°F) or Celsius/Centigrade (°C)
Conversion: F = (1.8xC)+32 C=(F/1.8)-32
 no need to memorize these equations
Water Boils at 212°F and Freezes at 32°F (100 & 0 °C)
Heat is defined as ‘the total Energy of all Molecules (illustrated by
their motion) within a substance’
 Temperature is therefore defined as ‘a measure of molecular motion,
using a man-made scale’
 Heat, and therefore Temperature affects air Pressure and Density,
and is therefore VERY important information for Pilots
 e.g. high temperature = lower density = LESS LIFT

Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
8
Weather Elements

Pressure



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A gas pressing on another, or a surface results in Pressure
Atmospheric Pressure is the effect of air pushing down on
the Earth’s surface
As molecules collide, movement results
Measurement of Atmospheric Pressure:
 Mercury Barometer - Accurate, Reliable and Stable, used by
Scientists
 Aneroid Barometer - Fast and Easy to Read, but not particularly
accurate
 Aneroid Barograph - Provides a permanent record of pressure
changes, using a pen and a revolving drum of paper

Atmospheric Pressure affects air density, and differences
causes bodies of air to move, thus creating wind.
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
9
Moisture and Clouds

Moisture
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Moisture is Water in Solid (Ice), Liquid (Water), or Gaseous
(Vapor) form
The air can only hold a limited amount of water vapor, when is
contains the maximum amount, it is Saturated
Saturation depends on temperature, the temperature at which
the air WILL become saturated is called the Dew Point
Add more moisture, or decrease the temperature BELOW the
Dew Point, and Condensation (conversion to liquid) occurs
 Clouds and Fog are both forms of Condensation
Humidity describes the amount of moisture in the air
 The normal measure is Relative Humidity, which is the % of
saturation which has been reached, e.g. 70%
 Fog - mass of water droplets in suspension (Ground Level Cloud)

Occurs when Temp & Dew Point are within 5° and wind is low
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
10
Moisture and Clouds
 Clouds


Like Fog, Clouds are a mass of water droplets in suspension,
but they can also contain ice crystals, or water / ice mixed
There are 3 basic Cloud Forms:
 Cumulus - White, Billowy, Puffy (Cotton Balls), Low Level
– Normally seen in good weather, but also associated with turbulence

 Stratus - Thin, Sheet like, Grey, Low Level
 Cirrus - White, Thin, Wispy, High Level
Precipitation

When the temperature fall too far below the Dew Point, and the
Cloud can no-longer hold the moisture in suspension,
Precipitation Results
 Either Rain, Snow or Ice (hail) depending on temperature
 Precipitation is measured with a Rain Gauge
 Precipitation reduces Visibility, and makes runways slippery
 Ice increases Aircraft weight, and can block inlets
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
11
Weather Systems and Changes

Air Masses - A HUGE mass of air
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Normally at least 1000 miles across
Essentially the same Temperature and Moisture
characteristics throughout
Air masses are classified by where they came from, i.e. their
Source Region
The 6 Source Regions are:
 cA - continental Arctic
 cP - continental Polar
 cT - continental Tropical
 mT - maritime Tropical
 mP - maritime Polar
 mE - maritime Equatorial
Maritime masses are wetter
Farther away from the equator = a colder mass
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
12
Weather Systems and Changes

Fronts - the boundary between 2 air masses:

WARM Fronts ride up over Cold Air
 Normally COLD Fronts are heavy and low,
and push Warm Fronts up, and away
 When similar air masses meet, there may not be
enough difference to cause movement, and a
STATIONARY Front occurs
 An OCCLUDED Front (3 air masses) the Warm
air is still pushed up, but relatively cool air is
pushed up also by colder air
 Cold Occluded - Old Cool Air pushed up,
basically like a Cold Air snowplough, pushing
everything Upwards
 Warm Occluded - New
Cool Air pushed up
behind Warm Air, by
local colder air
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
13

Weather Systems and Changes
Severe Weather


Cumulonimbus clouds are a sign of Severe Weather, which
could be a Thunderstorm, Tornado or Hurricane
Thunderstorms
 Heavy Winds, Strong Rain, Sometimes Hail
 Lightning - Electric Discharge, which can heat the air to 60,000°F!
– About 200 are killed and 600 injured by lightning in the US annually!
– 3 stages: Building (Updrafts), Mature (Up/Down air cycles),
Dissipating (Downdrafts)
 Do’s and Don’ts:
–
–
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–
–
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–
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Don’t use electric appliances, telephones, or take a shower
DO Stay away from Windows and Doors
If Outdoors, DO go Inside
If in a car, DO stay there
If in a boat, DO get ashore
DO Move away from Water and Metal objects
Don’t stand in open space, or under a tree
DO Stay Low, and Don’t huddle in a group
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
14
Weather Systems and Changes

Tornadoes
 Fujita Wind Damage Scale - F0 to F5, with wind speed range and
expected scale of damage for each
– F5 is over 261 MPH, with ‘Incredible’ Damage resulting
– Do’s and Don’ts:
» DO Get to a Basement (or lie down in low ground)
» DO, If above ground, move at 90° to the Tornado
» DO, if indoors, stay away from windows, got to the interior, or
into a closet or bathroom

Hurricanes
 Saffir-Simpson Hurricane Damage Potential Scale Cat 1 (75-95 MPH), to Cat 5 (155+ MPH!), with Pressure Range,
Wind Speeds, and Storm Surge (Sea Level increase)
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Do’s and Don’ts:
same as Thunderstorms & Tornadoes, since they can produce BOTH
Worse, they can be HUGE, and can continue for more than a week!
But, Hurricanes have a ‘Eye’ at the center which is calm
Dr. R.A. Bartholomew
-
Civil Air Patrol, New Jersey Wing
15