Meteorology Flashcards
troposphere
hight of the troposphere is 25,000 to 35,000 ft. in the polar regions, and 50,000 to 60,000 ft in the equatorial regions.
most of flying done in this region
all weather found in this region, due to all the moisture being in it.
tropopause
the top of the troposphere.
found at 25,000 - 30,000 ft in the polar region, and
55,000 - 65,000 ft in the equator region
decrease in temperature stops at the tropopause
SALR
(standard lapse rate) (standard atmosphere)
-2ºC/1000ft
DLAR
dry adiabatic lapse rate
-3ºC/1000ft
MALR
saturated adiabatic lapse rate (moist adiabatic lapse rate)
-1.5ºC/1000ft
A Stable Atmosphere
when environmental lapse rate (ELR) is shallow or even negative.
when lapse rate is negative it is an inversion.
the atmosphere is stable because any air which rises will cool adiabbatically and in doing so will cool more rapidly than the surrounding air which cools at the environmental lapse rate. because rising air cools faster than its surroundings, it will sink back after rising. this is a stable situation
An Unstable Atmosphere
when environmental lapse rate (ELR) is steeper than both the dry (DLAR) and wet (MALR) lapse rates.
any air which is forces to rise and cools adiabatically will end up being warmer than the surrounding atmosphere. as a consequence, it will then be lighter than the surrounding air which will then cause it to rise further and in doing so increase the temperature difference between itself and the surrounding air, and so on.
A Conditionally Unstable Atmosphere
when the environmental lapse rate (ELR) is somewhere between the dry and adiabatic lapse rates
Environmental Lapse Rate
the rate at which the temperature decreases with altitude.
primary causes of weather
uneaven heating of the surface of the earth
season variations
latitude variations
diurnal (day/night) variations
different surfaces of the earth absorbing heat differently, i.e. water land
ISA
international standard atmosphere
temperature at sea level is 15ºC
ELR is 2ºC/1000ft
pressure at sea level is 29.92 or 1013 hpa (millibars) or 14,69 psi
atmosperic pressure drops by approximately 1” of mercury for every 1000ft
hight of the tropopause is 36,090 ft
convection
vertical movement of air
advection
the horizontal movement of air
sublimation
when a solid changes phase directly to a gas
deposition
when a gas changes directly to a solid
coriolis force
force which causes the moving air to be deflected to the right (clockwise) in the norther hemisphere and to the left (counterclockwise) in the southern hemisphere
low pressure system
air circulates counter clockwise around a low pressure area in the northern hemisphere
forms a trough when they have an elongated shape
lows are usually associated with rising air, and the arrival of cloudy weather and precipitation
high pressure systems
air circulates clockwise around a high press system in the northern hemisphere
when it is elongated it formed a ridge
highs are normally associated with defending air, and clear weather with a gentle wind
gust
a rapid increaes in a wind speed for a short period of time before retuning to the average speed
squall
a rapid increase in wind speed lasting for a minute or longer
squalls may also be caused by a line of thunderstorms which often occur along a front, in which case they are known as line squals
veering
when the direction from which the wind blows increases, for example, when the wind changes from a southernly to a south-westerly direction
downburst
a very strong localized downdraft from a thunderstorm
high clouds
has “cirro” in the name
above 20,000 ft
cirrus: clouds with a streaky fibrous appearance
cirrostratus: a thin layer
cirrocumlus: a small puffy clouds which give the appearance of being flattened
middle cloud
has “alto” in the name
between 6,500 - 20,000 ft.
altostratus: uniform layer of cloud
altocumulus: puffy clouds usually patchy
altocumulus castellanus: puffy clouds which grow to a significant height
low clouds
no prefix in name
with a base below 6,500 ft
stratus: uniform layer of cloud
nimbostratus: a dark layer cloud which usually produces continuous precipitation, be it rain sleet snow or freezing rain
fractostratus: this is strays cloud with gaps in the layer which gives the appearance of the layered cloud having been torn apart or fractured
Cumulus: puffy cods often grouped together.
clouds of vertical development
cumulus clouds which grow vertically into towering cumulus or cumulonimbus (thunder) clouds.
how to calculate cloud base
take the difference between the temperature and due point spread and divide by 3.
eg
temp:20º dew point: 5º
spread is therefore 15º
divide 15 by 3º
get 5.
therefore, cloud base is at 5000 ft, due to 3º/thousand ft over the temp dew spread.
sea breeze
wind coming from the water, due to the land heating during the day
land breeze
wind coming from the land, due to the land cooling, and the water acting as a heat sink, retaining heat better
chinook
when air containing significant amount of moisture blows toward a mountain range and is forced to rise. in the process, the air cools adiabatically. eventually the moisture will condense given the right circumstances. the air then blows down the other side of the mountain, however it now no longer contains the moisture. as it blows down the other side of the mountain, it warms adiabatically, and due to the fact that it is now dry, will be significantly warmer then when it originally warmed up.
mountain waves
lentuclar clouds
sever turbulence and wind shear
downdrafts
altimeter to read incorrectly
radiation fog
usually forms on clear nights when there is a gentle wind blowing. the cooling surface cools the air, and as the dew point is reached, visible moisture occurs.
advection fog
occurs when air flows from a location where the surface is relatively warm to now which is relatively cool.
frontal fog
associated with a front, warm or cold.
arctic sea smoke
forms through a process of evaporation and re-condensation. when cold air flows over a relatively warmer water, the water warms the layer of air closest to the water and evaporation. like coffee steam.
upslope fog
forms when air which is forced to rise cools adiabatically. if the upslope and moisture content is sufficient then the dew point will be reached and condensation will occur.
air masses
body of air with substantially the same properties of temperature humidity stability and tropopause height.
continental arctic: dry very cold and stable
maritime arctic: moist cold and unstable
maritime polar: moist unstable
maritime tropical: hoist hot very unstable
fronts
a boundary zone between two air masses where a large change of temperature occurs within a relatively short distance. the name of a front is derived from the name of the colder air mass
nautical miles to feet
1 nautical mile = 6,000 ft
how to estimate the position of a frontal surface
take altitude, convert to miles
take frontal slope ratio
multiply by converted altitude.
occlusion
occurs when a cold front catches up with a warm front. this forces the warm air aloft, forming a trough of warm air aloft, known as a trowel.
thunderstorms
form from convective clouds (however, not all convective clouds form thunderstorms)
requiers lifting agent
turbulence extreem
hail
icing
low visibly
low ceiling
lightning
downdrafts
microbursts
passing through a cold front
winds will usually veer and increase
temperature will start warn, and then drop suddenly.
dew point will usually fall
presure will decrease steadily, then will level off, and then increase steadily.
back
the direction from which the wind blows decreases, for example, the wind changes from an easterly to a north easterly direction.
convection
distribution of heat due to daytime heating of the surface of the earth
compression
heating by compression
stable air descends into areas of higher pressure at lower altitudes
frontal lift
warm less dense air rises over a cold front
orographic lift
air is forced aloft over mountains by strong winds
convergence
lifting caused by air drawn into the centre of a low
adiabatic cooling by expansion
as air expands it will cool
air rising into lower pressure will expand and cool, and often condense into a cloud
adiabatic heating by compression
as air sinks it will enter an area of higher pressure and the air is compressed and heated
stability
biggest determinant as to whether an airmass is stable or unstable is governed by lapse rate.
high lapse rate = unstable
low lapse rate = stable
stable air resists convection while unstable air promotes it.
divergence
high pressure pushes air down, and it diverted in every direction once it hits the ground.
under reading
altimiter will read lower than your actual altitude (you are higher than indicated). will occur in warmer air, lower pressure air.
from high to low, look out below
from hot to cold, don’t be bold
over reading
altimeter will read higher than your actual altitude (you are lower than indicated). will occur in colder higher pressure air
from high to low, look out below
from hot to cold, don’t be bold
pressure altitude
the altitude read when set to 29.92 hg
density altiude
pressure altitude adjusted for non-standard temperature.
used to calculate aircraft performance.
true altitude
the indicated altitude corrected for non-standard temperature between the surface and the altitude at which you are flying
dominent airmass in canada
winter cA or continental arctic
summer mA maritime arctic
arctic airmass
most north
polar airmass
just below arctic, vancouver
surface analysis charts
issued 4 times a day 0000z 0600z 1200z 1800z
FG
fog
PR
partial
MI
shallow
BC
patches
DR
drifting
BL
blowing
SN
snow
DU
dust
SA
sand
SH
shower
RA
rain
PL
ice pellets
GR
hail
GS
snow pellets
FR
freezing
DZ
drizzle
BR
mist
FU
smoke
HZ
haze
VA
volcanic ash
TS
thunder storm
SS
sand storm
DS
dust storm
VC
in the vicinity
SQ
squalls
+FC
tornado or waterspout
NS
nimbostratus
ST
stratus
SC
stratocumulus
SF
stratus fractus
CU
cumulus
CUFRA
cumulus fractus
AS
altostratus
AC
altocumulus
ACC
altocumulus castellanus
CI
cirrus
CS
cirrostratus
CC
cirrocumulus
TCU
towering cumulus
CB
cumulonimbus
GFA
6 charts issued 4 times per day forecasting up to 24,000 ft
amended by AIRMET AND SIGMET
2 charts valid at the start of the forecast period
2 charts valid 6 hours into the forecast period
2 charts valid 12 hours into the forecast period
issue times: 2330, valid at 0000 0530, valid at 0600 1130, valid at 1200 1730, valid at 1800
upper level wind chart winds above 100 knots
subtract 50 from the wind direction and add 100 knots to the speed.
in order to display three digit speeds, direction will be +50, in order to signify that 100 needs to be added to the speed.
icing
can resuce lift by 30%. decreased take off and climb performance reduced stalling angle of attack increased take off and landing speed increased weight reduced controllability airframe vibration
frost
usually forms overnight from an aircraft parked outside overnight. frozen water vapour accumulates on the airframe
clear or glazed ice
transparent
associated with the slow freezing of large supercooled water droplets on an airframe.
typically encountered in cumulus type clouds in temperatures from 0º to -10º
rime ice
rough milky appearance
associated with rapid freezing of small supercooled water droplets on an airframe
typically encounter in layer stratus type clouds in the temperature of -10º to -20º
clean aircraft concept
frost ice or snow myst be removed from critical surfaces of an aircraft prior to flight
if your landing with ice
increase approach speed to 20-25%
avoid extending flaps
fly a stabilized approach
do not make abrupt control inputs
delay extending the landing gear until the runway is assured
be aware of the increased landing distance requirement
worst conditions for picking up ice
thin wings
high speed
throughout a cloud with large droplets
high liquid water content
high efficiently of ice pick up is bad
▲▲▲ solid line with blue triangles
cold front
◗◗ solid line with red semicircles
warm front
