Met exam
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When air rises, its pressure falls and causes it to cool. The rate at which temperature of air falls as altitude increases is called the lapse rate.
The dew point is a measure of how much water vapour (invisible moisture) is in the air. When the actual temperature is equal to the due point, the air can hold no more water vapour and it is said to be 'saturated.'
Air whose temperature is above the dew point cools at 3 deg C for every 1000 feet increase in altitude -- the DALR dry adiabatic lapse rate. When air continues to cool to temperatures below the dew point, it cannot hold so much water vapour. So some of the water vapour condenses into tiny visible droplets and you have cloud.
The process of condensation gives out heat, so when saturated air rises it cools (like unsaturated air), and excess water vapour condenses out as cloud, but the effect of the heat given out is to reduce the rate at which the temperature falls. Saturated air cools at 1.5 deg C per 1000 feet increase in altitude -- the SALR saturated adiabatic lapse rate.
Coming to the question:
The temperature on the ground is 20.5 deg C. Air from the ground rises and (the temperature being above the dew point) cools at 3 deg C per thousand feet. The air temperature reaches the dew point 1500 feet; water condenses out and cloud forms.
So the calulation is:
20.5 - 16 = 4.5
4.5/3 = 1.5 thousand feet
ie 1500 feet.
The actual variation in temperature with altitude is not exactly as described above due to variations in the atmosphere and to other warming and cooling effects (other than expansion of the air as altitude increases), hence the actual lapse rate between two levels will be different. To complicate things further, the lapse rate in the standard atmosphere of about 2 deg C per thousand feet is also rarely found in the real atmosphere.
Pretty much everybody has trouble with this at first, so don't be disheartened.
AA.
The dew point is a measure of how much water vapour (invisible moisture) is in the air. When the actual temperature is equal to the due point, the air can hold no more water vapour and it is said to be 'saturated.'
Air whose temperature is above the dew point cools at 3 deg C for every 1000 feet increase in altitude -- the DALR dry adiabatic lapse rate. When air continues to cool to temperatures below the dew point, it cannot hold so much water vapour. So some of the water vapour condenses into tiny visible droplets and you have cloud.
The process of condensation gives out heat, so when saturated air rises it cools (like unsaturated air), and excess water vapour condenses out as cloud, but the effect of the heat given out is to reduce the rate at which the temperature falls. Saturated air cools at 1.5 deg C per 1000 feet increase in altitude -- the SALR saturated adiabatic lapse rate.
Coming to the question:
The temperature on the ground is 20.5 deg C. Air from the ground rises and (the temperature being above the dew point) cools at 3 deg C per thousand feet. The air temperature reaches the dew point 1500 feet; water condenses out and cloud forms.
So the calulation is:
20.5 - 16 = 4.5
4.5/3 = 1.5 thousand feet
ie 1500 feet.
The actual variation in temperature with altitude is not exactly as described above due to variations in the atmosphere and to other warming and cooling effects (other than expansion of the air as altitude increases), hence the actual lapse rate between two levels will be different. To complicate things further, the lapse rate in the standard atmosphere of about 2 deg C per thousand feet is also rarely found in the real atmosphere.
Pretty much everybody has trouble with this at first, so don't be disheartened.
AA.
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.. so to summerise... if a cloud has not formed use DALR of
3 deg/1000' as it is clear (dry) air under the cloudbase....
Cloubase calculations use DALR which is all you are likely to require at PPL level.
SALR and DALR are used to calculate cloud bases either side of a mountain ridge.. the Fohn effect.
In this case air uplifted by terrain cools at DALR until the dewpoint is reached ( cloudbase on the windward side) and thereafter cools at the SALR until the summit is reached.
Precipitation is assumed to have taken place, and the air on the leeward side has a higher dewpoint, which in turn gives a higher cloudbase as the air descends the lee slope cooling at the SALR.
This use to be a CAA favourite .. but that was a long tine ago !
3 deg/1000' as it is clear (dry) air under the cloudbase....
Cloubase calculations use DALR which is all you are likely to require at PPL level.
SALR and DALR are used to calculate cloud bases either side of a mountain ridge.. the Fohn effect.
In this case air uplifted by terrain cools at DALR until the dewpoint is reached ( cloudbase on the windward side) and thereafter cools at the SALR until the summit is reached.
Precipitation is assumed to have taken place, and the air on the leeward side has a higher dewpoint, which in turn gives a higher cloudbase as the air descends the lee slope cooling at the SALR.
This use to be a CAA favourite .. but that was a long tine ago !
Last edited by Teddy Robinson; 7th Jul 2004 at 23:37.
To get back to the original post, I've used AirQuiz and, in my opinion, it's the dog's danglies and well worth every penny.
I've done more Met courses than I can remember and passed more Met exams than any human being should be subjected to, but it's one of those subjects that I have to learn every time, nothing stays in my head longer than about an hour when it comes to Met.
Good luck, you'll get there.
I've done more Met courses than I can remember and passed more Met exams than any human being should be subjected to, but it's one of those subjects that I have to learn every time, nothing stays in my head longer than about an hour when it comes to Met.
Good luck, you'll get there.
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I think references to the Fohn effect are confusing the issue even more - it is an ATPL subject.
FWIW, the Thom method of calculating cloudbases is incompatible with the exam as it excludes the SALR. The PPL confuser provides the exam compatible calculation...both of which are slightly different from the ATPL!!
The 90+% exam method is to read Thom, then go through the section in the PPL Confuser thrice.
FWIW, the Thom method of calculating cloudbases is incompatible with the exam as it excludes the SALR. The PPL confuser provides the exam compatible calculation...both of which are slightly different from the ATPL!!
The 90+% exam method is to read Thom, then go through the section in the PPL Confuser thrice.
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Hi PBD,
I think that, to take and pass exams, you have to be a bit ruthless with yourself. It can be a slog, especially if you have many other things to do in your everyday life, as I do, and all the more so if those other things are not associated with flying.
My method is:
Read the Trevor Thom Book. Do every test question it sets for every chapter, or part-chapter, and write your answers in a book. The ones you get wrong, you correct your answer, go back, read the relevant para/s and understand why the answer was wrong.
When you have got to the end of the book, go back and read it again, but you can skim through it because you will remember much. Do the questions again - yes, again! Write the answers down, so that it’s a real test for you.
Make a short-list of the questions you got wrong the second time, and test yourself again on all of those wrong ones. When you have all of the Thom questions right, get someone to select any question from the book, and answer as in a conversation. Then move on to the Confuser.
Compile your own exam from the Confuser - in Met there are 109 questions, and like questions are grouped with like, and you need to separate them. 109/20 means select the questions 5 numbers apart, ie, the first exam is Q1, Q6, Q11, Q16 etc. Your next exam is Q2, Q7, Q12, Q17, and so on.
Those questions you have wrong in each of your own exams, read the Confuser answer - not always exactly the same as the Thom books, as has been said by others here (and, yes, I remember that question, the answer was nowhere to be found in the Thom, only in the Confuser!). When you have done all of the exams, do them again. Your pass mark will be going up. Then, make a list of all of the questions you got wrong. That is your last test. When you can answer all of the Confuser questions and get all of them right, that is the time to go and take the real Met exam. Not before.
You will by then have a pretty thorough knowledge and understanding of the subject, and will have the confidence of having sat your own exams and done well in them.
And, all through the studies, pull off the 214’s and 215’s, and the TAFs and the METARs, every day from the MET, and study them. It becomes fascinating.
I find I have to work at these exams. It can be hard work. But, I enjoy it, and I like to learn; and I love to fly.
Met is tough, but it will all fall into place. Don’t let it discourage you!
TP
I think that, to take and pass exams, you have to be a bit ruthless with yourself. It can be a slog, especially if you have many other things to do in your everyday life, as I do, and all the more so if those other things are not associated with flying.
My method is:
Read the Trevor Thom Book. Do every test question it sets for every chapter, or part-chapter, and write your answers in a book. The ones you get wrong, you correct your answer, go back, read the relevant para/s and understand why the answer was wrong.
When you have got to the end of the book, go back and read it again, but you can skim through it because you will remember much. Do the questions again - yes, again! Write the answers down, so that it’s a real test for you.
Make a short-list of the questions you got wrong the second time, and test yourself again on all of those wrong ones. When you have all of the Thom questions right, get someone to select any question from the book, and answer as in a conversation. Then move on to the Confuser.
Compile your own exam from the Confuser - in Met there are 109 questions, and like questions are grouped with like, and you need to separate them. 109/20 means select the questions 5 numbers apart, ie, the first exam is Q1, Q6, Q11, Q16 etc. Your next exam is Q2, Q7, Q12, Q17, and so on.
Those questions you have wrong in each of your own exams, read the Confuser answer - not always exactly the same as the Thom books, as has been said by others here (and, yes, I remember that question, the answer was nowhere to be found in the Thom, only in the Confuser!). When you have done all of the exams, do them again. Your pass mark will be going up. Then, make a list of all of the questions you got wrong. That is your last test. When you can answer all of the Confuser questions and get all of them right, that is the time to go and take the real Met exam. Not before.
You will by then have a pretty thorough knowledge and understanding of the subject, and will have the confidence of having sat your own exams and done well in them.
And, all through the studies, pull off the 214’s and 215’s, and the TAFs and the METARs, every day from the MET, and study them. It becomes fascinating.
I find I have to work at these exams. It can be hard work. But, I enjoy it, and I like to learn; and I love to fly.
Met is tough, but it will all fall into place. Don’t let it discourage you!
TP
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bnarna
I certainly can't help directly but I can say that discussing issues here has definitely helped so ask away and someone is sure to be able to help. As far as the technical is concerned I may be able to help but not the Met!!!
I fortunately work for a well known ATC provider and there are losts of PPL holders and instructors who I have got a lot of help from in Met. I am now at the point where I am consistently getting 80% to 85% and even a few times 90% and once 95% using example papers created from the PPL confuser, the Oxford training CD-ROMs and airquiz.com. So.....I am just about ready to have my first crack at this!!!!
I certainly can't help directly but I can say that discussing issues here has definitely helped so ask away and someone is sure to be able to help. As far as the technical is concerned I may be able to help but not the Met!!!
I fortunately work for a well known ATC provider and there are losts of PPL holders and instructors who I have got a lot of help from in Met. I am now at the point where I am consistently getting 80% to 85% and even a few times 90% and once 95% using example papers created from the PPL confuser, the Oxford training CD-ROMs and airquiz.com. So.....I am just about ready to have my first crack at this!!!!
Thread Starter
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Well....I took my met exam on Saturday and passed with 85%
For me that is a huge milestone passed!!!
Now I can concentrate on the other subjects which I have a much better grounding knowledge in.
Thanks for all your help!
For me that is a huge milestone passed!!!
Now I can concentrate on the other subjects which I have a much better grounding knowledge in.
Thanks for all your help!
