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## Meteorology KDRs

• Kenny Powers
• Topic Author

### Kenny Powers created the topic: Meteorology KDRs

Hi guys,

I finished my final CPL(H) subject last week, with a pass in Met. It was my weakest subject and unfortunately I came away with a few KDRs as a result. I'd appreciate it if you could help me answer a few that I can't find in Bob's book. I have put an asterix next to the answer I selected. I have tried to recall the questions and available answers as best I can, but obviously KDRs are designed so you're only provided with the syllabus items.

If the Environmental Lapse Rate increases with height, the atmosphere is said to be:

Unstable*;
Stable;
Conditionally stable;
Conditionally unstable.

The conditions a pilot would encounter flying above a small cumulus cloud:

Bumpy*;
Severe turbulence;
Calm;
Updraughts.

The following question relates to inversions and their effect on flight conditions:

A pilot is on approach to an airfield and has been flying into a strong headwind. He then enters an inversion layer, what effect does this have:

Reduced risk of carburettor icing*;
Increase in airspeed;

I can't remember the other answers unfortunately.

Thanks for your help, and thanks for providing us aspiring pilots with excellent material to get us through the theory aspect of our commercial licences.

• Posts: 1169

### Richard replied the topic: Meteorology KDRs

Hi Kenny,

Question 1:
If the ELR increases with height then the environment is cooling more rapidly as you go up in the atmosphere. Without knowing what the actual lapse rates were it is a hard call on this one. However, if SALR < ELR < DALR then you will have conditional instability (or conditional stability). According to the BOM's Manual of Meteorology the terms are interchangeable. That means answers (c) and (d) are identical.
If you have an increasing ELR, I doubt you would have a stable atmosphere so (a) would appear the best choice for the question stem you have given.

Question 2:
The turbulence comes from moving through bodies of air of different velocities. For example simple thermal activity gives rise to turbulence as different surfaces produce different rates of heating and therefore thermals of different vertical intensity. Within one of those updraughts the flying conditions may well be fairly smooth.
A cumulus cloud contains updraughts and as the air rises and cools adiabatically, the typical cauliflower-like, cumiliform cloud forms. The cumulus cloud tops are the upper edge of the rising air so generally, above the cumiliform clouds, the flying conditions will actually be quite smooth. Interestingly, between bodies of cumiliform clouds, there will usually be widespread areas of downdraughts as air sinks to replace the air rising below and within the cumulus type clouds.

Question 3:
If there is an inversion layer near the ground, there will be little wind happening within the inversion. If there was, the inversion would deepen and weaken until it eventually disappeared altogether. If the pilot moved from a body of air moving rapidly opposite to her direction of motion (i.e. the "strong headwind") into a body of air with little movement, the aircraft is effectively suffering a drop of headwind. Therefore you would expect a drop in airspeed and a loss of lift. There would also probably be some chop as the aircraft transitioned into the inversion layer as the higher speed air above whipped the upper surface of the inversion creating turbulent eddies and a region of horizontal shear.

Good luck with your career and thanks for some interesting questions!

Cheers,

Rich

• Kenny Powers
• Topic Author

### Kenny Powers replied the topic: Meteorology KDRs

If you have an increasing ELR, I doubt you would have a stable atmosphere so (a) would appear the best choice for the question stem you have given.

I would have thought so too (as that was the answer I selected), however I ended up with a KDR for atmospheric stability and from memory that was the only question I had on it.

Have a great christmas, I'm looking forward to lots of flying in the new year.

• Posts: 1169

### Richard replied the topic: Meteorology KDRs

Happy New Year Kenny,

After doing some more thinking about your second question, I have changed my answer there. I reckon the conditions will actually be calm above the cumiliform cloud.

Cheers,

Rich

• Klaaysen

### Klaaysen replied the topic: Meteorology KDRs

Hey guys,
It sounds like a radiation inversion.
I have a feeling the answer to question 1 is a 'stable' atmosphere (somewhat).
Reason being a rising parcel of air will struggle to remain warmer that the environment due to the increasing temperature with height.
At ground level it may well be warmer and begin rising, but eventually (and relatively quickly) the rising air and environment air will become the same temp, and the rising parcel will cease to do so.
Are there any other instances when temperature increases with height other than a radiation inversion?