SALR
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I thought it was only smoking that went on behind the bike sheds! 
Seriously, the official answer is 1.8 per 1000 feet, and the one I would use in the exam, possibly with a scribbled note as you hand your paper in. As I said it's clearly in the LOs and is obviously what they intend. My comment should have read .... "the answer is wrong, but they still want you to use it."
If I get a chance I will talk to Camelia who I believe still has charge of the CQB - watch this space.....
Phil
Just curious - if helipilot22 is using BGS notes, and "a certain school in coventry" uses BGS notes under licence (and if they're not, they're sure both using Framemaker), isn't there a screw up somewhere? Maybe there is a typo between the licence levels.
Seriously, the official answer is 1.8 per 1000 feet, and the one I would use in the exam, possibly with a scribbled note as you hand your paper in. As I said it's clearly in the LOs and is obviously what they intend. My comment should have read .... "the answer is wrong, but they still want you to use it."
If I get a chance I will talk to Camelia who I believe still has charge of the CQB - watch this space.....
Phil
Just curious - if helipilot22 is using BGS notes, and "a certain school in coventry" uses BGS notes under licence (and if they're not, they're sure both using Framemaker), isn't there a screw up somewhere? Maybe there is a typo between the licence levels.
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Could this ansewer your Q
LAPSE RATES
--------------------------------------------------------------------------------
This innocent section is actually one of the keys to understanding local scale weather changes.
Free Convection: this refers to air parcels that are heated initially throught contact with the surface (also called lapse rate steepening). The pavements of a town will have a very different albedo to the grass of its parks, or the surrounding fields.
Air parcels over the surface with greatest absorbing properties will be 'superheated': developing a higher temperature and lower density than the surrounding air. Density changes because the heat makes the particles move faster and more energetically meaning that there are larger spaces between them as the air mass expands.
The warmer, less dense air rises from the surface like a hot air balloon and rises up through the surrounding air. It will continue to rise as long as it remains warmer than the surrounding air. If the temperatures equalise, the air will diverge horizontally. If it is cooled below the air it will descend: one such area of subsiding air can be found in the 'eye' of a hurricane.
Forced, or mechanical convection is the vertical transfer of energy by currents in the atmosphere in response to obstructions. This takes place along fronts, such as the Polar Front where the 2 converging air masses have different temperatures and densities. It also occurs when there is an orographic barrier. This mixes air with different temperature and density and causes circulations which can lead to the formation of depressions (cyclogenesis)
The troposphere normally cools with height from the surface. This rate of cooling is known as the Environmental Lapse Rate (ELR) which is a variable rate (I often say, like my mortgage, but in fact I have a capped rate...) - an average figure is 6.5ºC per 1000m, but it varies with time, seasons, humidity (water vapour is mainly found close to the ground surface), short term changes in insolation, height etc. This usually relates to a large mass of stationary air and is the air through which other parcels will rise due to free or forced convection.
It is around 1000 times greater than the temperature change occurring horizontally due to changes in latitude, so it is a relatively rapid change in temperature.
Lapse rate steepening, also called super-adiabatic conditions occur on very hot days. The skin of air close to the earth accumulates large amounts of heat, and the temperature drops sharply above the ground. This creates extreme instability, and the development of thunderstorms. The term instability is a key one when considering lapse rates.
It is also worth noting that under certain conditions, the temperature can actually rise when moving up from the ground surface. This is known as a temperature inversion.
As a parcel of air rises up through the surrounding air it expands, as it descends it contracts. Heat is used up as the air expands. Balloons burst on reaching high levels. Descending air parcels warm as they are compressed. No heat enters or leaves the parcel, hence the term 'adiabatic'.
The rate of temperature change for unsaturated 'dry' air is 10ºC per 1000m (a fixed rate) - higher than the average ELR. This is known as the Dry Adiabatic Lapse Rate (DALR)
Rising parcels of air can reach the dew point: the height at which condensation begins to occur - also known as the cloud base. At this point, water vapour condenses and latent heat is liberated.
This rate is known as the SALR (Saturated Adiabatic Lapse Rate), and is variable depending on the amount of water vapour. A typical value for temperatures below 30 degrees Celsius is 5ºC per 1000m, increasing to 7 degrees below freezing point.
Stability occurs when the ELR is less than the DALR. Rising air will cool faster than the surrounding air and soon reach equilibrium. Air parcels will only rise due to forcing in this situation. Fair weather cumulus humilis are the only likely clouds to be created.
When the ELR is lower than both DALR and SALR, absolute stability occurs.
Absolute instability occurs when the ELR is greater than both the DALR and the SALR in the lower and middle troposphere.
Conditional instability occurs when the ELR lies between the DALR and the SALR and is a more common situation.
LAPSE RATES
--------------------------------------------------------------------------------
This innocent section is actually one of the keys to understanding local scale weather changes.
Free Convection: this refers to air parcels that are heated initially throught contact with the surface (also called lapse rate steepening). The pavements of a town will have a very different albedo to the grass of its parks, or the surrounding fields.
Air parcels over the surface with greatest absorbing properties will be 'superheated': developing a higher temperature and lower density than the surrounding air. Density changes because the heat makes the particles move faster and more energetically meaning that there are larger spaces between them as the air mass expands.
The warmer, less dense air rises from the surface like a hot air balloon and rises up through the surrounding air. It will continue to rise as long as it remains warmer than the surrounding air. If the temperatures equalise, the air will diverge horizontally. If it is cooled below the air it will descend: one such area of subsiding air can be found in the 'eye' of a hurricane.
Forced, or mechanical convection is the vertical transfer of energy by currents in the atmosphere in response to obstructions. This takes place along fronts, such as the Polar Front where the 2 converging air masses have different temperatures and densities. It also occurs when there is an orographic barrier. This mixes air with different temperature and density and causes circulations which can lead to the formation of depressions (cyclogenesis)
The troposphere normally cools with height from the surface. This rate of cooling is known as the Environmental Lapse Rate (ELR) which is a variable rate (I often say, like my mortgage, but in fact I have a capped rate...) - an average figure is 6.5ºC per 1000m, but it varies with time, seasons, humidity (water vapour is mainly found close to the ground surface), short term changes in insolation, height etc. This usually relates to a large mass of stationary air and is the air through which other parcels will rise due to free or forced convection.
It is around 1000 times greater than the temperature change occurring horizontally due to changes in latitude, so it is a relatively rapid change in temperature.
Lapse rate steepening, also called super-adiabatic conditions occur on very hot days. The skin of air close to the earth accumulates large amounts of heat, and the temperature drops sharply above the ground. This creates extreme instability, and the development of thunderstorms. The term instability is a key one when considering lapse rates.
It is also worth noting that under certain conditions, the temperature can actually rise when moving up from the ground surface. This is known as a temperature inversion.
As a parcel of air rises up through the surrounding air it expands, as it descends it contracts. Heat is used up as the air expands. Balloons burst on reaching high levels. Descending air parcels warm as they are compressed. No heat enters or leaves the parcel, hence the term 'adiabatic'.
The rate of temperature change for unsaturated 'dry' air is 10ºC per 1000m (a fixed rate) - higher than the average ELR. This is known as the Dry Adiabatic Lapse Rate (DALR)
Rising parcels of air can reach the dew point: the height at which condensation begins to occur - also known as the cloud base. At this point, water vapour condenses and latent heat is liberated.
This rate is known as the SALR (Saturated Adiabatic Lapse Rate), and is variable depending on the amount of water vapour. A typical value for temperatures below 30 degrees Celsius is 5ºC per 1000m, increasing to 7 degrees below freezing point.
Stability occurs when the ELR is less than the DALR. Rising air will cool faster than the surrounding air and soon reach equilibrium. Air parcels will only rise due to forcing in this situation. Fair weather cumulus humilis are the only likely clouds to be created.
When the ELR is lower than both DALR and SALR, absolute stability occurs.
Absolute instability occurs when the ELR is greater than both the DALR and the SALR in the lower and middle troposphere.
Conditional instability occurs when the ELR lies between the DALR and the SALR and is a more common situation.
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Hi,
The Saturated Adiabatic Lapse Rate (SALR) is the lapse rate for rising air which is saturated (RH 100%). It has an average value in temperate latitudes near the ground of 1.8 C/1000 ft or 6 C/1000m.
SALR is not constant, varying with temperature and approaching DALR as temperature decreases and/or increases.
All according to Oxford Meteorology (revised edition) p.9-1
The Saturated Adiabatic Lapse Rate (SALR) is the lapse rate for rising air which is saturated (RH 100%). It has an average value in temperate latitudes near the ground of 1.8 C/1000 ft or 6 C/1000m.
SALR is not constant, varying with temperature and approaching DALR as temperature decreases and/or increases.
All according to Oxford Meteorology (revised edition) p.9-1
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Happily everyone's right (probably). PPL coursebooks refer to the figure as 1.5 Deg C per 1000 ft, for the ATPL writtens (and I would have presumed the CPLs) it's referred to as 1.8 deg. Still doesn't explain why WBs notes say 1.5 though. Maybe it is 1.5 for the CPL?
FI course coming up and reviewing the PPL material again. :Insert suitable smiley:
FI course coming up and reviewing the PPL material again. :Insert suitable smiley:
It could be because using degrees per 1000m is appropriate to SI units whereas degrees per 1000 ft is not. I suspect that the old school of imperial measurements left it at 1.5 as it was easy to remember yet the new school JAA etc have complied with SI units but converted it to deg/1000' for ICAO commonality.
Out of interest the SALR curves are usually seen on a tephigram and the SALR rises with altitude as less moisture is avaliable to condense and release latent heat so the parcel of air behaves more like a dry gas.
Out of interest the SALR curves are usually seen on a tephigram and the SALR rises with altitude as less moisture is avaliable to condense and release latent heat so the parcel of air behaves more like a dry gas.
Thats it...it just popped for me...the fact that some met books refer to the lapse rates in degrees C per 1000 FEET and others refer to the rates in degrees C per 1000METRES...in Australia, the Trevor Thom met bood uses SALR 1.5degC/1000ft...the the australian met manual they use the degrees/meter figures (don't have the manual handy at the moment.
HP
HP
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thanks to everyone that replied,there is still some conflict about the salr rate i was told and studied it to be 1.8 now the cd for ppl is saying 1.5 degree.so which one to use for there ppl exam is still a mystery.
Hovering AND talking
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I think tu154 hit the nail on the head! PPLs and CPLs are not bright enough (that's me included BTW!) to be able to cope with a "difficult" number like 1.8 and therefore we are only allowed to deal with 1.5 deg/1,000 ft.
When we grow up into ATPLs, then we can use the slighter higher number
Alternatively, maybe global warming has changed the rate and some books are a little out of date!
Cheers
Whirls
PS - the last bit is NOT to be taken seriously!
When we grow up into ATPLs, then we can use the slighter higher number
Alternatively, maybe global warming has changed the rate and some books are a little out of date!
Cheers
Whirls
PS - the last bit is NOT to be taken seriously!
