Download Air masses - Andreas Lammering

Weather
Atmosphere
ICAO standardatmosphere
78% nitrogen, 21%oxygen, 1%other gas → remains
constant up to 70,000 ft
half of the mass is under 5,5km (500hPa)
Tropopause 8km, -45°C – 11km, 56,5°C – 16km, -75°C
Pic
Topopause
Higher over equator than poles
equator – 16 km / -75°
poles – 8 km / -40°
60N in winter → 29.000ft
40N in summer → 47.000ft
Charts
Lapse rates
Dry adiabatic lapse Rate: 1°C /100m
saturated adiabatic lapse Rate: 0.6°C/100m
Surface weather chart
Isobaren, spaceing 5 hPa
Upper airchart
Isohypsen, given height in decameter
850 hPa 1.5 km FL050
700 hPa 3 km
FL100
500 hPa 5.5 km FL180
Air masses
300 hPa 9 km
FL300
250 hPa
FL330
200 hPa 12 km
FL390
100 hPa 16 km
FL520
SWC
Significant weather chart
update 0:00,6:00, 12:00, 18:00
Definition
Airmass: an airmass with no horizontal difference in
Temperature
Lapse rate
Loss of temperature with height, negative numbers air
gains temperature
ISA Standard lapse rate 0.65° / 100m
Dry adiabatic lapse rate: 1°/100m
Saturated adiabatic lapse rate: 0.6°/100m
Fronts
Classification of
airmasses
Equatorial air masses
20° N to 20°S most unstable / high humidity
Tropical air masses
20°N to 30° N/S
Polar air masses
40° to 60° N/S in summer until 90°N/S
Arctic air masses
60° to 90° N/S
only in winter times, hight difference to Polar air mass 10°
to 15°C
cold air mass → colder than surface/surrounding air mass
warm air mass → warmer than surface/ surrounding air
mass
Humidity
maritime air masses - wet
continental air masses - dry
airmasses only mix in an thin layer (frontal layer)
Front: transition zone where the frontal layer hit the
surface
Polar front
Border between polar and subtropical
Position:
summer Newfoundland – North Scotland
winter: mediterranean aera
Westerlies / westerly weather
Weather very changeable
new cold front every 1-2 day
Warm front
Slides over cold air,
average gradient 1/150
front 800 – 1,500km
Clouds: CI-CS-AS-NS
Transition zone
Thickness: 50-100 km
Cold front
Pushing against the warm air
average gradient 1/80
front 400- 800 km
movement roundabout 50% faster than a warm front
Clouds: stable air: ST-NS-AS / unstable:ST-CB
Frontal waves
Bending of a stationary front.
Westerly Situation:
mid-latitudes every 1-2 days a new Front
Warm sector
Air mass between an cold and a warm front
Secondary depression
Tends to move around the primary
Cold occlusion
Cold front catch warm front.
Warm air mass push up (upper warmfront)
Wind
Warm occlusion
Especially in winter
Friction layer
2,000 ft to 6,000ft
surface friction cause a slow down
corioles force decrease → air flows out of a hight and in a
low.
deviation from normal gradient wind:
over land
30° and a decrease in speed by 50%
increasing height → veers (turns right) +
decreasing height → backs (turns left) over sea:
10° and decrease in speed only 30%
Jet streams
Occur on the front of main airmasses
nearly always west-winds
length, width and vertical extend of a midlatitude jetstream
1000NM; 150NM ; 18,000ft
arctic JS (only winter)
20,000ft
60-80°
80kt
Polar front JS N/S
30,000ft
40°-70°wi
50°-80°su
200kt
slower
subtropical JS N/S
40,000ft
20-35°wi
35-45°su
100kt
equatorial JS (july,
Eastwind)
50,000ft
Ca. 10°N
60-100kt
polar night JS (only
winter,stratosphere)
Geostrophic
Straight isobares
Deflection of wind by coriolis force
Pressure gradient = Coriolis
Gradient
curved isobares
Influenced by centrifugal force
low pressure = zentrifugal against pressure force → low
wind speed
Hight pressure = zentrifugal same direction like pressure
force → high wind speed
Windshear
Vertical windshear: if speed change with altitude (but not
direction ? )
horizontal windshear
Cloud base
Dew point diff. X 400 = cloud base in feet
Dew point diff. X 125 = cloud base in meters
Types
Stratus → lifting process, small water drops
alto-stratus: water and ice crystals
Cumulus → convection,
moderate to huge water drops
Clouds
Visibility
Fog < 1km
cumulus Cloud > 20 < 150m
stratocumulus >40<200m
altocumulus / altostratus >80m<300m
cirrus >1000m
RVR:
Coverage
Few
Scattered
Broken
overcast
1-2/8
3-4/8
5-7/8
7-8/8
Ceiling
Special
FOG
Visibility < 1000m
radiation fog:
clam, clear night. Occurs mainly short after Sunrise
advection fog
airmass moving cold surface or
cold airmass over warm water (steam fog, arctic fog)
MIFG: layer of 5 ft
advection fog: warm air mass moves over cold surface
orographic fog: air is forced to rise
steam fog: cold air moves over warm water
Precipitation
Microburst
Coalescence process
Forming of precipitation without foceil. Drops collide and
form lager drops which fall out. → only light precipitation
(Drizzel)
Bergeron-Findeisen
(mid latitudes)
Forming of precipitation in mixed clouds. Snowflakes form
an grow. Then falling through the cloud melt and hit the
Ground. Requiered: one part of the cloud have to be <0°C
Freezing rain
Only form in temperature inversions
Hail
small hail
Only in Thunderstorm 5 – 50 mm
normal convective clouds 5mm
Snow pellets
Snow stars onto which super cooled water droplets have
frozen. White opaque pellet
Ice pellets
Less than 5 mm, frozen freezing Rain
Grail
Lage hail, only from CB
Time
1-5 Minutes
diameter max 4km
Weather
hazardous
Weather Reports
Tornado
Moving speed: 20-40kt
diameter: 100-140 meter
Tropical revolving strom
Greatest amount: North-west pazific (Japan, Taiwan,
korean, China Coastline)
METAR
Actual AD Report.
Wind velocity average 10 min before report
Terms:
CAVOK: 9999, NSC (under 5000ft), NSW
VV / Vertical Visibility only reported if ceiling is not
TREND
Additional to METAR vaild for max. 2h
landing forecast
SIGMET
Climatology
AIRMET
Changes for special airways
TAF
Terminal area forecast:
Forecast normal: given in the TAF (Standard 9h)
SPECI
Aviations special weather report
AD WRNG
Aerodrome warning
Advers weather conditions for A/C on Ground and
handling staff eg
Mediteran
Rain < 700mm