SALR

[r22-male]

anyone help,have my cpl(h) and while studying for it i was told that the SALR in met was 1.8 degrees per 1000 ft. Getting a ppl ground course ready i obtained a cd of met, and they are saying its 1.5 degrees per 1000 ft. can anyone enlighten me. thanks

[CVR]

r22-Male,

I hope i remember this correctly, its been a long time since i sat my Cpl exams,

The SALR (WET AIR) is 1.5 per 1000 ft
The DALR (DRY AIR) is 3.0 per 1000 ft
The ELR Standard ISA is 2.0 per 1000ft or to be precise 1.98 C/1000ft

Hopes this helps

CVR

If I'm wrong i do apologise:ugh:

[robsrich]

That is correct. These figures are used in Australian CPL exams, including IREX.

Not sure about ATPL though.

[helopat]

That is correct. These figures are used in Australian CPL exams, including IREX.
Not sure about ATPL though.

Yep, same in the ATPL met.

HP

[Gordy]

I have to say it--I have NEVER found a need to use these figures once during my aviation career---I'm glad everyone is learning them.........
Has anyone in the rotary world ever had a use for them?

[Ioan]

well i've not actually started my career - but isnt it the base of the rule of thumb that the cloudbase should be about 400 multiplied by the difference between temperature and dew point?

Ive got only vague memories (worrying since I sat met 3 months ago!), but its 400 feet (ie 1000 / 2.5) because the SALR is actually a curve not linear, so 2.5 is a better estimation that 3.

Of course I could be talking rubbish!

[paco]

The SALR can range from 4°C to as high as 9°C per 1000 m, but the average for JAA exam purposes (for lower levels anyway) is 6°C per 1000 m, or 1.8°C per 1000 feet (it's clearly written in the learning objectives).

And Gordy - if you want to make best use of your performance charts in mountains, lapse rates are very useful.

Phil

[Gordy]

The SALR can range from 4°C to as high as 9°C per 1000 m, but the average for JAA exam purposes (for lower levels anyway) is 6°C per 1000 m, or 1.8°C per 1000 feet (it's clearly written in the learning objectives).
And Gordy - if you want to make best use of your performance charts in mountains, lapse rates are very useful.
Phil
I knew I'd take a hit on that comment---like you say, those numbers can vary, therefore, based upon my experience and my kind of operations, learning those numbers have had no practical use for me.
I will admit that they may be useful to some out there, but I am one of those who does not like to learn numbers for the sake of it. I prefer to understand the practical applications of weather.
If for no other reason, than some may learn something, or find it interesting--in terms of mountain flying, especially for fire and other utility work, here is an example of the weather reports I use:
Fire Weather (http://fire.boi.noaa.gov/FIREWX/SFOFWFEKA.html)
What is often not taught to students is that there are many other sources of weather that may be more pertinant to helicopter operations than aviation weather reports. Lets face face it---aviation weather reports are geared towards flying from A to B, rarely will you get a detailed "spot" forecast.

[paco]

I hear you on aviation weather reports - it's got to the stage where I only look at them for legal reasons - of what use is a forecast that says "visibility will be 100 m in hill fog"? or "800 m in showers"? I want to know where the fog is! :)

I used to have a network of friends round the UK that I would ring up - much more efficient!

If I was running a company there again, I would have some of those creative britecams dotted around the country that you can access from the internet. I know there are some surf ones available in the West Country which are quite useful

Phil

[Gordy]

Have to agree with you there---I use webcams all the time---even the road report websites have good cams on them---I can check I5 in California almost from LA to Oregon on webcams.
For all the "new kids on the block"---think outside the box---Avaition weather reports are not always the best.......

[Whirlygig]

I am currently studying the ground school for CPL(H) (not ATPL) with a school in Coventry!

I have their Met file open in front of me just now and, large as life and twice as ugly, it hath writ, SALR = 1.5 deg C per 1,000 ft.

Paco, would there be a difference between the figures that a student would use for CPL exams and ATPL exams?

Cheers

Whirls

[helopat]

I am currently studying the ground school for CPL(H) (not ATPL) with a school in Coventry!

I have their Met file open in front of me just now and, large as life and twice as ugly, it hath writ, SALR = 1.5 deg C per 1,000 ft.

Paco, would there be a difference between the figures that a student would use for CPL exams and ATPL exams?

Cheers

Whirls

Mate,

I think the bottom line is this. Learn the book numbers for DALR and SALR, do (and pass) the test, and you're golden. This stuff is just general knowledge of the world we live (and fly) in...the meteorologists (or weather guessers as I like to call them) are the ones who use this data (DALR, SALR, and ELR) to determine what they THINK will happen today at your aerodrome and they then publish a 'weather guess' or, as some people call them, TAF's. Thats my take on this stuff.

All the best lads,

HP

[HillerBee]

Fully agree with Gordy and Helopat. It's all 'interesting' to know. Just pass the test and put it in the drawer with the other 80% of stuff to forget.

Gordy thanks for the Fire weather link, very interesting.

[Whirlygig]

That's all very well but ... if the JAA exams are based on one rate and the books from which I'm studying have another rate, it could mean getting a question wrong which, in my case, could be the difference between pass and fail!!!! :}

When the questions are all multi-guess, there is no scope for error; if they were written, I would still get some credit for the right method even if the wrong rate were used.

Cheers

Whirls

[HillerBee]

SALR = saturated adiabatic lapse rate 1.5 CºC per 1000 ft.
ELR = environmental lapse rate 2ºC per 1000 ft. (ISA, standard lapse rate)

So SALR doesn't mean Standard Adiabatic Lapse Rate, maybe the confusion lies there.

[Whirlygig]

I don't think anyone's mentioned Standard ALR; but two people have clearly mentioned that 1.8 deg/1,000 ft is used for JAA purposes.

The other thought is whether the 1.8 deg/1,000 ft is derived from "iffy" conversion and rounding factors from the 6 deg/1,000m as quoted by paco.

Obviously, I shall stick with 1.5 deg/1,000 'cos that's what I've learned but, if I get one of those questions wrong, then somebody will get duffed up behind the bike sheds; not sure who yet!!

Cheers

Whirls

[topendtorque]

Hmmmmm - RULE # 1.

Obviously, I shall stick with 1.5 deg/1,000 'cos that's what I've learned but, if I get one of those questions wrong, then somebody will get duffed up behind the bike sheds; not sure who yet!!

Cheers

Whirls

RULE # 2.

I am positive that I remember it being 1.725 recurring over down under here Whirls!

[paco]

Based on the usual standard of JAA questions I would think that the 1.8 degree figure is wrong! :) Certainly I was originally taught that it was 1.5.

Phil

[ukhelipilot22]

I am studying ATPL (H) at BGS and the figure quoted in the manuals is 1.8 deg per 1000ft at sea level in temperate climates.:confused:

[Whirlygig]

Based on the usual standard of JAA questions I would think that the 1.8 degree figure is wrong! :) Certainly I was originally taught that it was 1.5.

Phil
paco - are you just making sure it's not you whom I duff up behind the bike sheds?! :} :p

UKhelipilot22 - perhaps the tactic is to work out two answers to an SALR question; one using 1.5 and the other using 1.8 and see which answer is one of the choices. However, if they're both there - it's 50:50 innit?!

Cheers

Whirls

[paco]

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.

[tomotomp]

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.

[Vertolot]

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 :=

[Vertolot]

Sorry,

Correction, ...the DALR as temperature decreases and/or altitude inreases.

[tu154]

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:

[[email protected]]

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.

[helopat]

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

[r22-male]

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.:{

[Whirlygig]

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!