The warmer the air, the higher the tropopause. The colder the air, the lower the tropopause. Generally over the poles, the tropopause can be between 8 -10 km and over the equator 16 – 18 km

Most of the weather is due to presence of water vapour, and the troposphere has almost all the weather

Presence of water means humidity

Most of the weather is due to presence of water vapour, and the troposphere has almost all the weather

Presence of water means humidity

THE CONSTITUENTS OF THE ATMOSPHERE

Nitrogen 78 % Argon 0.95% Oxygen 21 % Carbon Dioxide 0.05%

Plus traces of:

Neon Nitrous Oxide Helium Nitrogen Dioxide Krypton Carbon Monoxide Xenon Sulphur Dioxide Hydrogen Ammonia Methane Iodine and Ozone Water Vapour

Of all the trace gases, water vapour is by the far the most significant. Without it there would be no weather.

Since temperature decreases with height it goes to follow that the temperature at the tropopause is controlled by its height. The higher it is, the colder the temperature at the tropopause. The lower it is, the warmer the temperature at the tropopause. The temperature at the tropopause can be as high as -40°C over the poles and as low as -80°C over the equator. However, on average the tropopause is at about 11 km where its temperature is -56.5°C.

The warmer the air, the higher the tropopause. The colder the air, the lower the tropopause. Generally over the poles, the tropopause can be between 8 -10 km and over the equator 16 – 18 km.

As per isa fl 200 should have

(20x-2*) plus 15= -25 as temperature

(-2 being lapse rate)*

but actual is -35

which is 10° colder

The temperature at the tropopause can be as high as -40°C over the poles and as low as -80°C over the equator.  As in the diagram the tropics are close to equator, so you can interpolate the answer

Lapse rate is 2°C per 1000 feet of climb

if temperature at fl50 is 0°C and you climd 3000 feet

that is fl80

you will get -6°C

Temperature at Fl 110 is-5°C

We have to calculate the isa deviation

lapse rate = -2°C per 1000 feet

And temp at msl is 15°C

hence temp under isa should be= -22°C  plus 15°= -7°C

isa deviation is = 2°C

now at flight level 5000

as per isa temp should be 5°C

applying the deviation we get 7°C

as per table pressure altitude is 30000 feet

As per isa 30000 should have

(30x-2*) plus 15= —45°c as temperature

(-2 being lapse rate)*

but temp is -30°

hence it is HIGH

as per the table 200 hpa is 38000 feet

at 38000 feet temp as per isa should be

( using 2° lapse rate and 15° msl)

(38x-2)plus 15=-61°c

Within +/-5°C of ISA

DALR HUMIDITY LESS THAN 100%

LAPSE RATE IS 1 PER 100 METRE

SALR HAS 100% HUMIDITY

LAPSE RATE IS O.6 PER 100 METRE

DALR HUMIDITY LESS THAN 100%

LAPSE RATE IS 1 PER 100 METRE

SALR HAS 100% HUMIDITY

LAPSE RATE IS O.6 PER 100 METRE

ELR IN REAL DOESNT HAVE ANY FIXED VALUE

ISA CONDITIONS ARE TAKEN FOR CALCULATIONS

Inversion is also called negative lapse rate

Where the temperature increases with an increase in height, then we have what is called an inversion. We have already seen that at night we can expect an inversion above the surface, but this can occur in many different ways.

IT IS absolutely stable

If upper part has warm air that means temperature is increasing with height

and

If the ELR is less than 0.6°C / 100 m, the air is stable – absolute stability

here we have negative elr

THE ELR CONTROLS STABILITY.

€If the ELR is less than 0.6°C / 100 m, the air is stable – absolute stability.

Stable weather Bad visibility Nil to Light turbulence Stratiform cloud Intermittent to continuous precipitation DZ, -RA, RA, SN

€If the ELR is greater than 1°C/100 m, the air is unstable – absolute instability.

Unstable weather Good visibility (poor in showers) Moderate to severe turbulence Cumuliform cloud Showery precipitation SHRA, SHRA, GR, GS

 If the ELR is between 0.6°C and 1°C/100 m, the air is stable if dry and unstable if satu-rated – conditional instability.

 The clouds which form in stable air tend to be small in vertical extent and large in hori-zontal extent – layer clouds / stratiform cloud.
 The clouds which form in unstable air tend to be large in vertical extent and small in horizontal extent – heap clouds.

if dry air is disturbed it will return to is original position, in other words the air is stable, however, when saturated air is disturbed it will continue to rise and it is unstable.

The clouds which form in stable air tend to be small in vertical extent and large in hori-zontal extent – layer clouds / stratiform cloud.

The clouds which form in unstable air tend to be large in vertical extent and small in horizontal extent – heap clouds.

LESS VERTICAL EXTENT MORE STABILITY

DALR HUMIDITY LESS THAN 100%

LAPSE RATE IS 1 PER 100 METRE

SALR HAS 100% HUMIDITY

LAPSE RATE IS O.6 PER 100 METRE

If the ELR is less than 0.6°C / 100 m,(6°c /1000m) the air is stable – absolute stability.

Stable weather Bad visibility Nil to Light turbulence Stratiform cloud Intermittent to continuous precipitation DZ, -RA, RA, SN

here the lapse rate is 2°c / 1000m

hence stable

THE ELR CONTROLS STABILITY.

 If the ELR is less than 0.6°C / 100 m, the air is stable – absolute stability.

Stable weather Bad visibility Nil to Light turbulence Stratiform cloud Intermittent to continuous precipitation DZ, -RA, RA, SN

 If the ELR is greater than 1°C/100 m, the air is unstable – absolute instability.

DALR LAPSE RATE IS 1 PER 100 METRE

HENCE ELR

exceeds the saturated adiabatic lapse rate

If the ELR is between 0.6°C and 1°C/100 m, the air is stable if dry and unstable if satu-rated – conditional instability.

Solar radiation heats the ground and then Atmosphere is heated from the ground  that is the reason why temperature reduces with height in troposphere

Negative lapse rate in stratosphere:

Inversion means increase in temperature with height

it occurs due to uv ray absorption by ozone

the transfer of heat or matter by the flow of a fluid, especially horizontally in the atmosphere or the sea

Sun in afternoon In mid latitude is overhead which causes heat which leads to convective activity

Conduction: heat is physically transferred by molecules by contact , ground gets heated by sun rays and air very close to the ground gets heated by conduction,

Convection in this process hot fluid is bodily xfered to the colder part of the fluid more than 70 % earth is covered by water hence convection is important

Since temperature decreases with height it goes to follow that the temperature at the tropopause is controlled by its height. The higher it is, the colder the temperature at the tropopause. The lower it is, the warmer the temperature at the tropopause. The temperature at the tropopause can be as high as -40°C over the poles and as low as -80°C over the equator. However, on average the tropopause is at about 11 km where its temperature is -56.5°C.

Stratosphere layer of the atmosphere is defined as that layer above the troposphere where the temperature  remains constant with an increase in height.

temperature shows a gradual increase with height, especially at the top, where the temperature is zero at 50 km. This is due to the absorption of the sun’s ultra violet radiation by the concentration of ozone at higher levels

DALR HUMIDITY LESS THAN 100%

LAPSE RATE IS 1 PER 100 METRE

SALR HAS 100% HUMIDITY

LAPSE RATE IS O.6 PER 100 METRE

ANY OTHER LASPE RATE IS ELR

DALR HUMIDITY LESS THAN 100%

LAPSE RATE IS 1 PER 100 METRE

SALR HAS 100% HUMIDITY

LAPSE RATE IS O.6 PER 100 METRE

The reason for the SALR variation with temperature The warmer the saturated air, the more moisture is contains and therefore the more condensation occurs when it rises and cools. Therefore, more latent heat is released to the air parcel. As a result, warm saturated air cools at a slower rate than 0.6°C/100m and cold saturated air cools at a faster than 0.6°C/100m. At high altitudes (and latitudes) temperatures are low, little latent heat is released and thus DALR and SALR are nearly the same. Conversely, at low latitudes and altitudes, temperatures are higher and consequently SALR is shallow.

Cirrus clouds are at a higher altitude (17000-45000 ft) hence dalr and salr are closest

Radiation, on a night of clear skies, will also result in a temperature inversion above the surface. This is called a Radiation Inversion.

In a high pressure system, air descends at the centre. As the air descends it will be heated adiabatically (more of this later) and will be warmer than the air at a lower level adjacent to the surface. This is called a Subsidence Inversion. Poor visibility is related to high pressure area

1. Inversion is also called negative lapse rate

Where the temperature increases with an increase in height, then we have what is called an inversion. We have already seen that at night we can expect an inversion above the surface, but this can occur in many different ways.

Temperature inversion, also called thermal inversion, a reversal of the normal behaviour of temperature in the troposphere (the region of the atmosphere nearest Earth’s surface), in which a layer of cool air at the surface is overlain by a layer of warmer air

this is also called nocturnal inversion which leads to

nocturnal radiation: radiation from the surface of the Earth at night, which exceeds the amount of incoming radiation from the atmosphere.

Inversion is also called negative lapse rate

Where the temperature increases with an increase in height, then we have what is called an inversion. We have already seen that at night we can expect an inversion above the surface, but this can occur in many different ways.

iso means equal

thermal means temperature

1. Inversion is also called negative lapse rate

Where the temperature increases with an increase in height, then we have what is called an inversion. We have already seen that at night we can expect an inversion above the surface, but this can occur in many different ways.

wind and cloud cover will cause T max to be reduced and T min to be increased.

WIND: wind will cause turbulent mixing of the warm air at the surface with cold air above, reducing T max.

Time in Paris is 1800 UTC

LOCAL TIME IS 0400 PM

As per diurnal variation of temperature

From 15:00 LMT onwards, the temperature falls continuously until a little after sunrise. The lowest temperature occurs at about sunrise plus 30 minutes. (TMIN)

it is past 1500 let by 1 hr

As per diurnal variation of temperature

From 15:00 LMT onwards, the temperature falls continuously until a little after sunrise. The lowest temperature occurs at about sunrise plus 30 minutes. (TMIN)

isobars are line joining places of the same atmospheric pressure

iso means equal

bar is related to pressure

Qff is the barometric pressure at the surface reduced to MSL using the observed temperature at the surface and it’s corresponding pressure lapse rate only used for charts

A line joining places of the same atmospheric pressure (usually MSL pressure QFF).

Qff is the barometric pressure at the surface reduced to MSL using the observed temperature at the surface and it’s corresponding pressure lapse rate only used for charts

The air in the lower layers of the atmosphere is compressed by the weight of the air above it. Consequently, air is denser, and atmospheric pressure is greater, at the Earth’s surface than at altitude

5500 metre is 18000 feet

closest is 20000 feet

Isohypse (aka height contour)
A line of equal geopotential height. Geopotential assumes the earth is perfectly flat and a perfect sphere. The geopotential height is the distance above the Earth’s surface if it was a perfect and flat sphere. Isohypse are shown on a constant pressure surface

Difference between qfe and qnh is elevation

With height of 8 metre pressure change is 1 hpa

With 200 metre pressure change is 25 hpa

Qfe at locarno is 980 hpa and it is at 200 mtrs amsl

Qnh will be at sea level 1005 hpa ,

Pressure increases as you descend in the atmosphere

Difference between qfe and qnh is elevation

With height of 8 metre pressure change is 1 hpa

With 200 metre pressure change is 25 hpa

qnh at locarno is 1015 hpa ( at msl)

Qfe should bet 200 mtrs ( above msl)

Qfe will be 1015-25 = 990 hpa

As you travel up in atmosphere pressure decreases

Difference between qfe and qnh is elevation

With height of 8 metre pressure change is 1 hpa

With 200 metre pressure change is 25 hpa

qnh at locarno is 1025 hpa ( at msl)

Qfe should bet 200 mtrs ( above msl)

Qfe will be 1025-25 = 1000 hpa

As you travel up in atmosphere pressure decreases

DENSITY IS DIRECTLY PROPORTIONAL TO PRESSURE

pressure is constant in this case

DENSITY IS INVERSELY PROPORTIONAL TO TEMPERATURE
Hence

temperature decreases density increases

Density altitude is pressure altitude corrected for nonstandard temperature

if temperature is standard 

density altitude is equal to pressure altitude

Refer the chart

500 hpa is 18000 pressure altitude

700 hpa is 10000 feet

Refer the chart

850 hpa is 5000 pressure altitude or fl50

as per table pressure altitude is 30000 feet

As per isa 30000 should have

(30x-2*) plus 15= —45°c as temperature

(-2 being lapse rate)*

but temp is 15 ° warmer

hence it -45 15

-30° Celsius 

Lapse rate in isa -2°C per 1000 feet of climb

And temperature is 15 ° C at msl

climbing 10000 feet we reduce -2°C every 1000 feet

hence temperature lost is -20°C

now add this to 15° C( temperature at msl)

result is -5°C

add 10°c.

We get 5°c

Freezing point is when temperature is 0°

if at FL 120 temperature is -2° then as per lapse rate

if we go 1000 feet below temp will increase by 2°

and at FL110 temp will be 0°

The ICAO ISA is defined as follows:-

a MSL temperature of 15°C¾ ¾

a MSL pressure of 1013.25 hPa¾ ¾

a MSL density of 1225 g/m¾ ¾ 3

a lapse rate of 0.65°C/100m (1.98° C /1000 ft) up to 11 km (36,090 ft)

a constant temperature of -56.5°C from 11 km (36,090ft) to 20 km (65,617 ft)¾ ¾

an increase of temperature 0.1°C/100m (0.3°C /1000 ft), from 20 km (65,617ft) to 32 km ¾ ¾ (104,987 ft)

The ICAO ISA is defined as follows:-

a MSL temperature of 15°C

a MSL pressure of 1013.25 hPa

a MSL density of 1225 g/m¾

a lapse rate of 0.65°C/100m (1.98° C /1000 ft) up to 11 km (36,090 ft)

a constant temperature of -56.5°C from 11 km (36,090ft) to 20 km (65,617 ft)¾ ¾

an increase of temperature 0.1°C/100m (0.3°C /1000 ft), from 20 km (65,617ft) to 32 km ¾ ¾ (104,987 ft)

since 250 hpa is halfway between 300 hpa and 200 hpa , altitude should be selected between 30000 and 38000

apse rate in isa -2°C per 1000 feet of climb

And temperature is 15 ° C at msl

climbing 10000 feet we reduce -2°C every 1000 feet

hence temperature lost is -20°C

now add this to 15° C( temperature at msl)

result is -5°C

add 10°c.

We get 5°c

The ICAO ISA is defined as follows:-

a MSL temperature of 15°C

a MSL pressure of 1013.25 hPa

a MSL density of 1225 g/m¾

a lapse rate of 0.65°C/100m (1.98° C /1000 ft) up to 11 km (36,090 ft)

a constant temperature of -56.5°C from 11 km (36,090ft) to 20 km (65,617 ft)¾ ¾

an increase of temperature 0.1°C/100m (0.3°C /1000 ft), from 20 km (65,617ft) to 32 km ¾ ¾ (104,987 ft)

Here we must apply two corrections. A barometric difference and a temperature difference. The baro comes first.

FL100 is a pressure altitude of 10 000 feet with the Kohlsman window (subscale) in the altimeter set to 1013.25 hPa (29.92″) in a standard atmosphere. If the pressure datum (QNH) for mean sea level is lower than ISA then our true altitude is LESS than indicated. (High to low, look out below.)

Here since the QNH is less than standard, by about 30 hPa, we are 810 feet lower than the altimeter says. If we were to remain in level flight and put into the Kohlsman window, the altitude indicated would be 9190 feet. Presuming no other ISA deviations, of course.

However we do have a temperature deviation. It is 15°C colder than ISA.

The temperature correction was

True Altitude = Indicated Altitude plus(ISA Deviation × 4/1000 × Indicated Altitude)

(4x -15×10 )= -600 feet

Add it to 9190

which puts us at about 8590 feet (although the altimeter tells us 10 thousand).

here we must apply two corrections. A barometric difference and a temperature difference.

if you want to apply both corrections either use this formulae

TA = IA (4 x IA/1000 x ISA Dev) (27 x (QNH – Subscale))

or

Apply pressure correction

pressure correction

1013-1003=13hpa

Which is =390 feet

As the altimeter should be set to 1013 but is set to 1003

Aircraft is flying 390 feet above , which is

15390

then temp correction

TRUE ALTITUDE = ALTITUDE ON QNH (ISA DEVIATION x 4 x PRESSURE ALTITUDE ÷ 1000)

Assume Alt on QNH = x

Isa deviation = – 15

15390 =[x ( -15x4x12000)/1000 ]

=16110

Ac is flying into high pressure

When flying from

Low to high altimeter will under-read

but True altitude is same

The true altitude of this surface will depend on the density of the air below flying from marseille  where the qnh is lower to Palma where the qnh is higher you would normally expect your true altitude to increase since true altitude remains constant it must be colder in Palma

in this case find indicated altitude

True Altitude = Indicated Altitude plus(ISA Deviation × 4/1000 × Indicated Altitude)

Remember this. For every 1°C deviation from ISA your altimeter is wrong by 4ft for every 1000ft you have.
In this case you have 15°C ISA Deviation. So 15 x 4 gives you 60ft error per every 1000ft. You are at 15000ft so 60 x 15 gives you a toal error of 900ft.
Its “warm” in the question, and when it’s warm TRUE ALTITUDE is more than INDICATED ALTITUDE.
So, to have a true altitude of 15000ft the indicated altitude must be 1410

true altitude increases in warmer atmosphere

Since both the places have same pressure it is obvious that we are flying to a warmer place

true altitude increases in warmer atmosphere

Since both the places have same pressure it is obvious that we are flying to a warmer place

true altitude increases in warmer atmosphere

rue Altitude = Indicated Altitude plus (ISA Deviation × 4/1000 × Indicated Altitude)

with all the info given we can find out the isa deviation of temperature but not the temperature

true altitude = indicated altitude

if there is no isa deviation

To know the temperature of the air you need to know two things, the indicated altitude on QNH and the true altitude. You know this because if it’s warmer than ISA

then TRUE > INDICATED

and if it’s colder than ISA

then TRUE < INDICATED.

In the question then, whilst you have the true altitude they have not given you the indicated on QNH. They have given you a flight level which you can use to work out the indicated on QNH. So, get off the flight level 1013 and onto 1003.

You now see that the INDICATED on QNH is 9730 FT. Notice that this is less than the TRUE altitude of 10,000ft. Therefore the TRUE altitude is more than the INDICATED altitude.

Looking back to the second paragraph this can only happen if the air is warmer!

As a thumb rule

if it’s warmer than ISA

then TRUE > INDICATED

and if it’s colder than ISA

then TRUE < INDICATED.

altimeter shows indicated altitude

hence lower altitude than summit

True Altitude = indicated  Altitude plus(ISA Deviation × 4/1000 × Indicated Altitude)

I.a = 20000

isa deviation = -15

ISA Deviation × 4/1000 × Indicated Altitude=  -15×0.004×20000 =-1200

True Altitude = indicated  Altitude plus(ISA Deviation × 4/1000 × Indicated Altitude)

=20000-1200= 18800

2nd

apply barometric correction

FL200 is a pressure altitude of 20000 feet with the Kohlsman window (subscale) in the altimeter set to 1013.25 hPa (29.92″) in a standard atmosphere. If the pressure datum (QNH) for mean sea level is higher than ISA then our true altitude is High than indicated.

Here since the QNH is more  than standard, by about 20 hPa, we are 540 feet higher than the altimeter says

Add 18800 plus 540

True Altitude = indicated  Altitude plus(ISA Deviation × 4/1000 × Indicated Altitude)

I.a = 16000

isa deviation = -10

ISA Deviation × 4/1000 × Indicated Altitude=  -10×0.004×16000 =-640

True Altitude = indicated  Altitude plus(ISA Deviation × 4/1000 × Indicated Altitude)

=16000-640= 15360

2nd

apply barometric correction

FL160 is a pressure altitude of 16000 feet with the Kohlsman window (subscale) in the altimeter set to 1013.25 hPa (29.92″) in a standard atmosphere. If the pressure datum (QNH) for mean sea level is lower than ISA then our true altitude is lower than indicated.

Here since the QNH is less  than standard, by about 10 hPa, we are 270 feet lower than the altimeter says

 15360 – 270=15090

Altimeter error = 4 ft per 1°C deviation from ISA for every 1,000 ft
(i.e. 0.004 ft per 1°C deviation from ISA for every 1 ft)

The airmass is 10 deg warmer than ISA so 4 x 10 = 40

The error is 40 feet per thousand feet and for 12000 feet the error will be 40 x 12 = 480 feet.

Now its a matter of adding or subtracting 480 feet from 12000 feet.

Since the airmass is warmer than ISA the true altitude will be greater than indicated altitude.

So if we plan to fly at the minimum (true) altitude of 12000 feet to clear the mountains the altimeter will show (indicate) less than true i.e. 12000 – 480 = 11,520 feet.

As a thumb rule

if it’s warmer than ISA

then TRUE > INDICATED

and if it’s colder than ISA

then TRUE < INDICATED

true altitude = indicated altitude

if there is no isa deviation

In N hemisphere

Starboard drift= flying into low pressure

Port drift= flying into high pressure

In S hemisphere

Starboard drift= flying into high pressure

Port drift= flying into  low pressure

flying from east to west

winds from north

port drift

in N hemisphere

port drift means flying Into high pressure

high pressure gives you gain in altitude

In N hemisphere

Starboard drift= flying into low pressure

Port drift= flying into high pressure

In S hemisphere

Starboard drift= flying into high pressure

Port drift= flying into  low pressure

Ac gets starboard drift due to winds from left

Starboard drift= flying into low pressure

When flying from

high to low altimeter will overread

Hence it is overreading the altitude in actual it has decreased

In simple words

qfe is pressure at the airfield

qnh is pressure at the sea level right below the airport

setting QFE will give the height of the aircraft from the airfield

setting QNH will give  height of the aircraft from the sea level( elevation)

if the airfield is below the sea level atmosphere will exert more pressure on the air field than sea level

1013 is isa standard pressure

in reality qnh is not fixed

if qnh set , it gives the elevation of a place

in this case it should be 1715 ft if the actual qnh is set

current elevation shown on the aircraft is 1310

difference in actual elevation and indicated elevation is

1715-1310=405

if 1 hpa reduces every 27 feet up

1 hpa increases every 27 feet down

405 feet = 15 hpa

and going down from 1013 it is 1028

the aircraft with setting 1013 pressure reading indicates altitude more than aircraft

with setting 1009 as the one with setting 1009 measures elevation from pressure level 1009 ,

hence reading will decrease

differnce in pressure

1013-993= 20

1hpa = 27 feet

20hpa=540 feet

with pressure setting 1013 altimetre measures elevation from a pressure level below 993

hence setting 993 will give lesser altitude

1200-540=660 feet

Forget about the part in which aircraft is at aerodrome with 1023 setting

at pressure altitude

altitude Measured from 1013 (SPS)setting

will be less than altitude measured at 1023 setting

elevation(1411) = difference between QFE and QNH =QNH-QFE

ELEVATION=1411 FEET

QNH=994 HPA

IN HPA ELEVATION=1411/27HPA=52 HPA

52HPA= 994HPA – QFE

QFE=994 HPA -52 HPA= 942 HPA

QNH IS HIGHER THAN QFE IF ABOVE MEAN SEA LEVEL

Baro meter reads 8000 feet (fl80) if set on 1013

if set on qnh = 1000 hpa it will read less than 8000 by 13 hpa

1 hpa = 27 feet

13 hpa =351 feet

800-351= 7649 feet

with qnh  1023 hpa elevation should show 290 feet

if we set the reading at 1013 it would show 10 hpa less than 1023 hpa

1 hpa = 27 feet

so

10 hpa  = 270 feet

difference is 20 feet

the difference in qnh and qfe is elevation

if we are at sea level qfe and qnh could be equal

QNH can be lower as well as higher than 1013.25 hPa

1013 is considered to be mean sea level pressure in isa condition (hypothetical)

altitude in cold atmosphere reads lower than the actual level

QFE = 995 hPa, elevation = 1600 FT (488m)

the difference qnh and qfe is elevation

1600 ft in hpa = 1600/27 =60 hpa

qnh = 1055

the difference qnh and qfe is elevation

in this case difference is 20 hpa

if 1 hpa = 8 meter

20 hpa = 160 metre

True altitude in High pressure or warm atmosphere is always more than cold/low ,

in this case it is warm atmosphere

select the option with more than 6000 feet thickness

as between fl 60 and fl120

thickness should be 6000 feet ideally , but with temp higher than standard would make it more thicker

True altitude in High pressure or warm atmosphere is always more than cold/low ,

“watch out below when you are low”

lowest value of qnh would assure the lowest level to descend to

highest -ve temp deviation ensures the same ,

anything above this would be safer hence these give the

lowest usable flight level

True altitude in High pressure or warm atmosphere is always more than cold/low ,

hence qnh more than 1013 and temp more than isa

“watch out below when you are low”

temp is colder than isa hence spacing is less than 1000 feet for sure

True altitude in High pressure or warm atmosphere is always more than cold/low ,

hence qnh more than 1013 and temp more than isa

“watch out below when you are low”

minimum safe altitude is a generic expression used to describe the minimum altitude that is needed to avoid obstacles or terrain

True altitude in High pressure or warm atmosphere is always more than cold/low ,

hence qnh more than 1013 and temp more than isa

“watch out below when you are low”

25 NAUTICAL MILE = 45 km

HENCE 45 KM/HR

WE HAVE TO CONVERT 90 KM/HR TO NAUTICAL MILES /HOUR

SO JUST CONVERT KILOMETER TO NAUTICAL MILE

1 KM = 0.539957 NM

90 KM = 49 NM

ANSWER IS 49 KNOTS

40 KNOTS =74 KM/HR

74 KM =74000 METRE

1 HOUR= 3600SECONDS

ANSWER =74000/3600= 20 M/S

Wind speed is usually given in knots, but some countries give the speed in metres per second and the Met.

Wind direction is always given as the direction from which the wind is blowing. It is normally given in degrees true, but wind direction given to a pilot by ATC or in an ATIS will be given in degrees magnetic.

In N hemisphere

Starboard drift= flying into low pressure

Port drift= flying into high pressure

In S hemisphere

Starboard drift= flying into high pressure

Port drift= flying into  low pressure

Ac gets starboard drift due to winds from left

Starboard drift= flying into low pressure

When flying from

high to low altimeter will overread

Hence it is overreading the altitude in actual it has decreased

Buys Ballot’s Law states that: If an observer stands with his back to the wind, the lower pressure is on his left in the northern hemisphere, and on his right in the southern hemisphere.

A corollary of this law is that if an aircraft is experiencing starboard drift in the northern hemisphere the aircraft is heading towards low pressure. This is illustrated below.

Gradient Wind In A Depression If air is moving steadily around a depression, then the centrifugal force opposes the PGF and therefore reduces the wind speed. You can see this on the left hand side of the image shown below.

The gradient wind speed around a depression is less than the geostrophic wind for the same isobar interval. Hence if the Geostrophic Wind Scale (GWS) is used, it will overread.

Gradient Wind In A High

Looking to the right of the diagram, if air is moving steadily around a high, then the centrifugal force acts with the Pressure Gradient Force (PGF), increasing the velocity of the wind.

The gradient wind speed around an anticyclone is greater than the geostrophic wind for the same isobar interval. Hence if the Geostrophic Wind Scale (GWS) is used, it will underread.

Wind flow is clockwise around a low in the S. hemisphere.

Flying away from the L means the wind must be from the left for it to also be flowing clockwise around the low.

Wind flow at Low altitude vs high altitude changes as a result of surface friction preventing flow being truly parallel to the isobars.

The pressure system mentioned is a Low so air will tend flow into the Low, in addition to clockwise around this S. hemisphere Low.

You’re flying away from the low at low altitude (therefore friction effects), the wind has a tendency to flow into the low so there will also be a slight headwind component.

Coriolis Force, (CF), is the force caused by the rotation of the earth.

It acts 90° to the wind direction causing air to turn to the right in the northern hemi-sphere and to the left in the Southern hemisphere. CF is maximum at the poles and minimum at the equator.

Wind is caused by air flowing from high pressure to low pressure. The Earth’s rotation prevents that flow from being direct, but deflects it side to side(right in the Northern Hemisphere and left in the Southern), so wind flows around the high and low pressure areas

In N hemisphere

Starboard drift= flying into low pressure

Port drift= flying into high pressure

In S hemisphere

Starboard drift= flying into high pressure

Port drift= flying into  low pressure

flying from east to west

winds from north

port drift

in N hemisphere

port drift means flying Into high pressure

high pressure gives you gain in altitude

The gradient wind occurs when the isobars are curved.

The Geostrophic Wind blows parallel to straight isobars.

Isohypse (aka height contour)
A line of equal geopotential height. Geopotential assumes the earth is perfectly flat and a perfect sphere. The geopotential height is the distance above the Earth’s surface if it was a perfect and flat sphere. Isohypse are shown on a constant pressure surface

The gradient wind occurs when the isobars are curved.

The Geostrophic Wind blows parallel to straight isobars.

Isohypse (aka height contour)
A line of equal geopotential height. Geopotential assumes the earth is perfectly flat and a perfect sphere. The geopotential height is the distance above the Earth’s surface if it was a perfect and flat sphere. Isohypse are shown on a constant pressure surface

Gradient Wind In A High

Looking to the right of the diagram, if air is moving steadily around a high, then the centrifugal force acts with the Pressure Gradient Force (PGF), increasing the velocity of the wind.

The gradient wind speed around an anticyclone is greater than the geostrophic wind for the same isobar interval. Hence if the Geostrophic Wind Scale (GWS) is used, it will underread.

the Geostrophic Wind Speed will increase as latitude reduces.

The higher the air density, the slower the geostrophic wind.

Geostrophic winds always move parallel to these isobars. The paths of geostrophic winds are referred to as geostrophic flow. The first major cause of geostrophic winds is the pressure gradient force, and the second is the Coriolis effect. This effect is the result of the rotation of the earth

the geostrophic wind speed is directly proportional to the horizontal pressure gradient–a doubling of the gradient results in a doubling of the wind speed

true altitude and indicated altitude remains same hence no cross wind

buy ballots law multipled by zero

As air rises, the air surrounding the low pressure area will be drawn inwards in an attempt to fill the low, and return the air pressure to equilibrium.  However, the inward-moving air will experience friction as it moves over the Earth’s surface, slowing it down.  Consequently, more air leaves the divergence area in the upper atmosphere than can be replaced at the surface.  Therefore, low pressure above the warm surface is maintained, and air pressure may continue to fall over time as this process evolves.

subtropical high, one of several regions of semipermanent high atmospheric pressure located over the oceans between 20° and 40° of latitude in both the Northern and Southern hemispheres of the Earth

Altocumulus lenticularis, also known as lenticular cloud, is found downwind of mountainous or hilly areas, and is indicative of the presence of mountain wave activity. Because of its position downwind of high ground, moderate or even severe turbulence may be found beneath altocumulus lenticularis. However, the air in the lenticular clouds, themselves, is always smooth.

Due to friction the surface wind is slower than the geostrophic (freestream) wind.

In NH the surface wind Backs.

In SH the surface wind Veers.

Due to friction the surface wind is slower than the geostrophic (freestream) wind.

In NH the surface wind Backs.

In SH the surface wind Veers.

In northern hemisphere at 2500 feet winds are southerly( from south).

as we know in northern hemisphere winds at ground will back , or turn anticlockwise hence they will become south easterly