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Basic Navigation Using Map
and Compass
Basic Navigation Using Map and Compass
Learning Outcome 5:
Be able to recognise weather conditions that affect
land navigation
Hot and Cold Air Masses
UK SUMMER
AUSTRALIA WINTER.
AUSTRALIA SUMMER
UK WINTER.
BECAUSE OF THE RELATIONSHIP OF THE EARTH’S
ORBIT AROUND THE SUN TO THE TIME OF YEAR,
THE ANGLE THAT THE SUN’S RAYS HIT THE EARTH
VARY WITH TIME.
MOISTURE IN THE AIR
ALL AIR CONTAINS MOISTURE.
IT IS ONLY THE AMOUNT THAT VARIES.
HOW THE AIR ARRIVES AT OUR SHORES
AFFECTS THE MOISTURE IN THE AIR.
IF IT HAS TRAVELLED OVER LAND IT IS MOST
LIKELY TO BE DRY. LITTLE MOISTURE.
IF IT HAS TRAVELLED OVER THE SEA IT IS MOST
LIKELY TO BE WET. LOTS OF MOISTURE.
MOISTURE IN THE AIR
THE AMOUNT OF MOISTURE SUSPENDED IN THE AIR
IS DEPENDENT ON THE AIR TEMPERATURE.
THE WARMER THE AIR THE MORE MOISTURE IT WILL
HOLD.
THE MOISTURE CANNOT BE SEEN UNTIL THE AIR
BECOMES SATURATED AND THE MOISTURE COMES
OUT OF SUSPENSION AND FORMS CLOUDS.
THE SATURATION POINT IS KNOWN AS THE ‘DEW POINT’.
THE TYPE OF CLOUD FORMED IS DEPENDENT ON THE
RATE OF TEMPERATURE CHANGE AND THE STRENGTH
OF THE WIND.
Main Air Masses
Width of the arrows indicates the
frequency of occurrence
Main Air Masses
ARCTIC MARITIME – VERY COLD AND WET/SNOW
POLAR MARITIME – COLD AND WET/SNOW
RETURNING POLAR MARITIME – COOL AND WET
TROPICAL MARITIME – WARM AND WET (GULF STREAM)
TROPICAL CONTINENTAL - HOT AND DRY
POLAR CONTINENTAL – COLD AND DRY IN WINTER
WARM AND DRY IN SUMMER
ICAO STANDARD ATMOSPHERE
• BASED ON SEA LEVEL
ACCEPTED AROUND THE WORLD
PRESSURE
1013.25 Mb
TEMPERATURE
15º C
LAPSE RATE OF -1.98ºC/1000Ft
Weather Map
WIND CIRCULATES
ANTI-CLOCKWISE
AROUND A ‘LOW’.
AND CLOCKWISE
AROUND A ‘HIGH’.
Fronts and Frontal Depressions
Numbers refer to pressure in millibars
Weather Map – Westerly Winds
Depression Chart
Depression
Fronts and Frontal Depressions
Section through a frontal system
Cold front is steeper than the warm front
High and Low Pressure
High and Low Pressure
Upper Winds
Weather map showing
isobars for both upper
and lower winds.
Lower winds affect
the weather we get.
Upper winds affect
the speed the weather
system moves.
SURFCE PRESSURE CHART – NORTH ATLANTIC & EUROPE
Names For Clouds
The names for clouds are usually combinations of the
following prefixes or suffixes:
Stratus/strato = flat/layered and smooth
Cumulus/cumulo = heaped up/puffy, like cauliflower
Cirrus/cirro = High up/wispy
Alto = Medium level
Nimbus/Nimbo = Rain-bearing cloud
CLOUD LEVELS
HIGH CLOUDS
BASE USUALLY 20,000ft OR
ABOVE OVER UK.
TYPES – CIRRUS
CIRROCUMULUS
CIROSTRATUS
MEDIUM CLOUDS
BASE USUALLY BETWEEN
6,500ft AND 20,000ft OVER UK.
TYPES – ALTO CUMULUS
ALTO STRATUS
NIMBOSTRATUS
BASE USUALLY BELOW
6,500ft OVER UK.
LOW CLOUDS
TYPES – STRATO CUMULUS
STRATUS
CUMULUS
CUMULONIMBUS
Approaching Rain
Warm Front
Cold Front
Occluded Front
Depression Cross Section
Cloud Type
Depression Cross Section
Air movement
TYPES OF CLOUD
TYPES OF CLOUD
TYPES OF CLOUD
TYPES OF CLOUD
TYPES OF CLOUD
CUMULONIMBUS CLOUD
TYPICAL ANVIL HEAD TO THE CLOUD
AS THE RISING AIR COMES TO A STOP
AND THE UPPER WINDS PULL THE
TOP CLOUD OFF THE COLUMN.
Local Warming
Pockets of Air
Thermals above
Air rising over mountains
Rising Air Dewpoint
Cloudy foothills
Funnels and Eddies
Banner Clouds
Temperature Inversion
stratus
cumulonimbus
cumulus
stratocumulus
Matches pressure chart
TYPES OF CLOUD
TYPES OF CLOUD