Meteorology Keynotes

the troposphere

varies drastically with latitude and with the seasons. In the polar region its between 25 000 - 35 000ft while in the equatorial regions its from 50 000 - 60 000ft

1. through the surface of the earth

2. short wave

this heats the earth which in turn re-radiates the heat at a much longer wave length which is absorbed by the atmoshphere

1. seasonal variations

2. latitude variations

3. diurnal (day/night) variations

4. Different surfaces of the earth, such as rock collects heat more than trees

1. travels through more atmosphere

2. spreads out over larger area and is therefore less intense than at the equator

3. strikes the surface at a more oblique angle

all this results in less heating at high alt

it provides a mechanism for transporting thermal energy to different parts of the globe. water is able to do this because it absorbs significant energy when it is heated and especially when it changes phase

1.98 degrees C per 1000ft

temperature inversion

3 degrees C per 1000ft

1.5 degrees C per 1000ft

15 degrees C

36 090ft

1 inch

greater

the amount of water in the air relative to the max which it can hold at that temp and pressure

if air is cooled at a constant pressure the temp at which condensation begins is known as the dewpoint. The closer the dewpoint temp is to the outside air temp, the more likely it is that clouds will form

less

poorer airplane performance will be

vertical movement of air

horizontal movement of air

when a solid changes phase directly to a gas without going through the liquid phase

when a gas changes directly to a solid without going through the liquid phase

these are line of constant pressure

lines of constant wind velocity

line joining points where the alt at which a specifies pressure occurs is constant

1. coriolis force which causes moving air to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere

2. friction with the surface of the earth. Friction forces are greatest below aprox 3 000 AGL

3. acceleration or centrifugal forces when the air is following a curved path

are felt by moving air as a result of the rotation of the earth about its axis. It depends on:

1. wind speed: the higher the wind speed, the higher the coriolis force

2. latitude: the higher the latitude, the higher the coriolis force. At equator, the coriolis forces are zero. at the poles they are max

1. polar cell

2. hadley cell

3. ferrel cell

sounterwards in the northern winter and vice versa in the northern summer

surface winds are more complex and influenced by the surface over which they are blowing (land, water, mountains, valleys etc)

1. air circulates counter-clowckwise in the northern hemisphere

2. known as troughs, especially when they have an elongated shape

3. surface lows are usually associated with rising (or ascending) air and the arrival of cloudy weather and precip

1. air circulates clockwise

2. if high pressure system is elongated is shape then it is referred to as a ridge of high pressure

3. associated with descending (or subsiding) air, clear weather and gentle wind

stronger

left

1. veer

2. back

3. not connected

a rapid increase in wind speed for a short period of time before returning to the average speed

a rapid increase in wind speed lasting for a minute or longer before returning to the average speed

may also be caused by a line of thunderstorms which often occur along a front in which case they are known as line squalls

when the direction from which the wind blows increases, for example when the wind changes from a southerly from an easterly to a north easterly direction

when the direction from which the wind blows decreases, ex wind changes from an easterly to a north easterly direction

very strong localized downdraft from a thunderstorm

a downburst which is less than 2 NM in horizontal extent and persist for less than 5min

a downburat which is greater than 2NM in horizontal extent and persist for between 5-20min

from

when air containing moisture (gaseous water vapor) is cooled to saturation resulting in the water condensing as liquid droplets or as crystals

1. adiabatic expansion resulting from lifting air

2. advection (horizontal movement) of air over a colder surface

3. evaporative cooling

1. the primary cause of the cooling is adiabatic expansion resulting from lifting of the air. Lifting can occur because of:

a. atmosphere convergence - where air masses clash horizontally and the air is left with no place to go other than up

b. orographic features - where air travels over orograpihc features such as mountains and is forced to rise

c. frontal action - where one air mass undercuts forcing the second air mass to rise or one mass rides over the top of another air mass

d. mechanical turbulence - similar in nature to lifting cause by orographic features

e. convection - where adjacent bodies of air are warmed (or cooled) differently usually by different ground surfaces. The body of air which is warmed more rises while the other body sinks

1. high cloud

2. middle cloud

3. low cloud

4. clouds of vertical development

base above 20,000 ft.

normally contain the word “cirro” or cirrus

cirrus = clouds with a fibrous or streaky appearance

cirrostratus = usually a thin layer

cirrocumulus = small puffy clouds which give the appearance of being flattened

base between 6 500 - 20 000 ft (alto)

altostratus = uniform layered cloud

altocumulus = puffy clouds usually patchy in their coverage

altocumulus castellanus = puffy clouds which grow to a significant height

base below 6 500ft. normally described by their appearance and do not have a preffix

stratus = uniform layered cloud

nimbostratus = a dark layer cloud which usually produces continuous precip, be it rain, sleet, snow, freezing rain

fractostratus = (sometimes called stratus fractus)/ this is a stratus cloud with gaps in the layer which gives the appearance of the layered cloud having been torn apart or fractured

cumulus = puffy clouds often grouped together. If they form a continuous layer then they are referred to as stratocumulus

are cumulus clouds which as their name suggest, grow vertically into towering cumulus or cumulonimbus thunderstorm clouds. the bases of these clouds can be in the lower (below 6 500ft) or middle (6 500 - 20 000ft) level and the tops can extend into the stratosphere in the extreme cases

sky is clear below 10 000ft as interpreted by an autostation

no clouds

clouds cover greater than zero and up to 2/8 of the sky

3/8 - 4/8

5/8 - just less than 8/8

8/8

mist = vis 5/8sm or greater

fog = vis is less than 5/8

height of the base of the lowest broken or overcast layer of cloud

difference between 20-5=15

divide 15/3=5

height of the base of the convective cloud will be 5 000ft AGL

(3 degrees C per 1000ft) calculation for cloud base for TC exam

created when a mountain or hillside is exposed to direct sunlight. The surface warms faster than the valley. The heated slope warms air in contact with it causing it to expand and rise. This draws in more cool air from the valley floor or in a circulation pattern

occurs as a result of a rapid radiation of heat from exposed mountain or hill slopes at night. particularly true of surfaces which are not covered with vegetation. Once the slopes have cooled they cool the air in contact with the slope causing it to increase in density and sink. This process draws in more air from above and displaces warmer air in the valley

sea breezes:

arise during the day because land masses warm up and much more rapidly than adjoining water masses. as land warms, it warms the air in contact causing the air density to drop. the lower density air is more buoyont than the surrounding air and thus rises. As the warmed air rises, its place is taken by the cooler air from over the eater setting up a circulation pattern.

land breezes:

at night land will cool off more rapidly than water. This cools the air in contact with it, increasing its density and causing it to sink. these are known as land breezes and are usually more gentle than sea breezes

occur when air containing a significant amount of moisture blows towards a mountain range and is forced to rise. in the process, the air cools adiabatically first at the dry adiabatic rate (3 per 1000) and if the mountain range is high enough, the moisture will condense reducing the rate of cooling to 1.5 per 1000. In this situation, clouds will form and precip will occur on the windward side, reducing the moisture content of the air. On the leeward side the air will sink and warm adiabatically. Only now the air no longer contains the moisture so all the warming will be at the dry adiabatic lapse rat (3 per 1000). As a result, the air will warm substantially more when it descends than it did when it was forced to rise and cool

when stable air is blowing towards a mountain range it is forced to rise. On the downwind or lee side of the mountains, the descends and bc of the terrain eddies and vortices are formed in the descent. The air compresses as it descends and then springs back. This creates an oscillating flow with its associated up and down drafts and often sever turbulence. If the air contains sufficient moisture, distinctive clouds will form in the regions where the pressure and temp drop providing warning signs. Lenticular clouds will form at the crests of the waves, while rotor clouds will form in the extreme turbulence of the eddies downwind. clouds may be hidden by other clouds

downdrafts, severe or extreme turbulence and the windshear. Downdrafts can reach speeds of up to 5000 ft per min and the most severe are usually found at the same height as the mountain ridge

altimeter may read incorrectly due to the pressure increasing and decreasing as the air oscillates like a spring

forms on clear nights with gentle wind (-5kts). on clear nights the surface of the earth loses heat through radiation into space. as the temp of the surface drops, it cools the air in contact. If the air contains sufficient moisture and the temp drop of the air is enough for the air to reach its dew point then condensation will occur and a cloud will form at ground level.

forms usually a few hours before dawn cause thats when the radiation cooling of the surface has been sufficient to cause condensation. a little wind is necessary to mix the air up as it flows over the surface so as to enable to surface to cool a layer of air for some thickness. if no wind only dew, no cloud. too much wind then there will be insufficient temp drop for the DP to be reached and for condensation to occur

Type of fog formed when warm, moist air moves over a cold surface, causing the air to cool and condense into fog.

ex. air flows from where it is located over a warm water current to a cool one, or where air flows from over a warm land mass to over a colder one

may form when the wind is blowing at greater speeds , up to 15kts depending on the temp difference between the air and the cool surface and the moisture content of the air

Type of fog that occurs when a warm front moves over a colder surface, causing condensation. It reduces visibility and forms a low-lying cloud near the ground. rain falling from the warm air mass into the cold air mass evaporates. the process of evaporation will cool the cold air further. this cooling in combo with the evaporation saturates the cold air which causes some re-condensation to occur into small suspended droplets forming a cloud. if it occurs at the surface then fog will form

forms through a process of evaporation and re-condensation. when cold air flows over relatively warm water, the water warms the layers of air closest to it and evaporation of the water occurs. The warmed air rises and then cools as it mixes with the colder air above and condensation occurs. As the warmed air rises further and mixes with more cold, dry air, the relative humidity drops and the moisture re-evaporates

forms when air which is forced to rise cools adiabatically. If the upslope and moisture content is sufficient then the dewpoint will be reached and condensation will occur

a body of air with horizontally uniform temperature, humidity, pressure and tropopause height

categorized by nature of the surface over which they were formed

1. continental arctic -cA

2. maritime arctic - mA

3. maritime polar - mP

4. Maritime tropical - mT

1. generally dry, very cold and stable with the tropopause at low alt

2. moist, cold, unstable in the lower layers with the tropopause at low alt

3. moist, unstable throughout with the tropopause somewhat higher

4. generally moist, hot, very unstable with a high tropopause

boundary zone between 2 air masses where a large change of temp occurs within a relatively short distance

the name is derived from the colder air mass involved in the front, while the type of front is derived from the advancing airmass.

ex. if a maritime polar and a maritime tropical airmass were to meet, with the warmer airmass (mT) advancing, then the front formed would be a mP warm front

the stability of the air in the warm sector

stratiform

cumuloform

very few clouds

wider

gradual

dependent on moisture content of the warm air mass and the slope of the frontal surface. which in turn depends speed of the front and the relative temperature of the air masses

195 NM

when a cold front catches up with a warm front, this happens bc the wind speed behind a cold front increases more than anywhere else in deepening low pressure system

warm front occlusion (less common)

it undercuts the warm air and forces it aloft forming a trough of warm air aloft, known as (trowal)

1. source of lifting agent or trigger

2. an adequate supply of moisture (to fuel the growth)

3. instability reaching the upper parts of the tropospher

1. developing or cumulus stage

2. mature stage

3. dissipating stage

primarily composed of updrafts (can reach speeds of 2 500 - 3 000ft per min:

-as the air rises and the temp drop, condensation occurs and small drops become large raindrops

above the freezing level, ice will begin to form

once the raindrops reach a size where the updrafts are not capable of supporting them, they start to fall dragging some of the air with them

begins when rain first reaches the surface:

cloud contains both up and downdrafts: updrafts can reach speeds up to 6000ft per min/ downdrafts up to 2500ft per min

-lightning and turbulence

-as the rain falls, evaporation will slow the compression heating

-updrafts can cause tops of clouds to reach 5000-6000ft into the stratosphere

-when downdraft first hits the surface it will spread out creating a gust front sometimes known as a plow wind

-entire area of the cloud becomes an area of downdraft which removes the source of the turbulence, hail, and lightning

based on the trigger which starts them growing

1. air mass: form within a warm, moist airmass which is not associated with a front. are generally isolated and scattered over a wide area

2. frontal: the initial source of lifting is cold air undercutting warm air at a cold front or warm air riding up over cold air at a warm front

1. form within a warm, moist airmass which is not associated with a front. are generally isolated and scattered over a wide area

2. orographic: where the initial source of lifting is provided by an orographic feature such as a mountain range

3. Convective: The initial source of lifting is convective heating associated with uneven heating of the surface of the earth

4. Nocturnal: form at night and where the initial source of lifting is convective heating of air by a warm body of water, land breeze action or cooling or a moist layer of air aloft at night