I believe this is not correct. Pitch and AoA are only distantly related.
They are not directly related, in general; and I didn't say they were. But they are directly related in a specific condition. If 1. pitch is the angle of the plane in relation to the horizon, with pitch == 0 when the plane is horizontal and 2. AOA is the difference between the axis of the plane and the angle of its current vector, then pitch will equal AOA at the point where the plane's vector of travel matches the horizon, e.g the plane is flying exactly level without gaining or losing altitude and the plane is not banking. When the plane's vector is perfectly horizontal, and the plane is not banking, pitch and AOA are directly related if not exactly the same thing.
Even if you take an up/down wind into account, this is still true. If there's a downward wind, the plane will need to fly at a higher pitch angle in order to maintain level flight. Nose up. The vector of the plane is still level, the nose is higher, thus the AOA is also increased. They are affected in exactly the same way, as long as the plane is flying exactly horizontal/level. You can do the same thought exercise with a head or tail wind. With increasing tail wind, if you keep the true velocity of the plane constant, it's like slowing the plane. And you will need a higher AOA/pitch to keep the plane flying perfectly level. Vice versa with a head wind.
Obviously, while descending/landing the plane's AOA will be greater than the pitch. And while climbing, the pitch will be greater than the AOA. This is because the angle of the plane's vector is no longer matching the horizon. The one reading is relative to horizon, the other is relative to current vector.
The movement of the airfoil through the air creates an apparent movement of such air and so the AOA varies with speed through air.
I'm sorry, this sentence has no meaning to me.
the AOA varies with speed through air.
This part has a meaning to me, and I believe it is wrong. The AOA where a plane will stall changes with speed and altitude, but the actual AOA does not. It is still the angle between the plane's nose-tail axis and the plane's vector and nothing here changes with speed. The AOA that a plane will utilize in order to maintain level flight will change with speed (because the wings will generate more lift, they won't need as high an AOA or pitch). Provided the pilot wants to keep the vector exactly level, the AOA utilized will decrease as the plane increases in speed. But it will decrease in the exact same way that the pitch does, because as long as the vector of the plane is exactly horizontal, the AOA and pitch will be exactly the same (plus or minus any offset depending on how you are defining the reference point or zero point for either one, which is basically just an arbitrary decision, one of which an engineer handles a hundred a day; this can also be looked at as a calibration difference).
Also the wing does not have to be parallel to the fuselage.
This is irrelevant to an engineer. Whether you define the AOA as the difference in angle between the plane's vector and its fuselage... or between the plane's vector and its wing angle, it really doesn't matter. You could define the AOA for a given plane to be the angle between its vector and some arbitrary line painted on the side of the plane, even, and it wouldn't matter. Each individual plane has it's own AOA limits, anyway, which is why in many planes the actual angle isn't even displayed, and AOA is just given as a corrected number between 0 and 1. And in any case, if expressed as the actual angle, you could use a fixed offset to convert one to the other, fuselage vs wing (in case they differ by a few degrees).
It is the same in sailing (with which I am more familiar with). Imagine the boat starting out motionless in the water with the wind right across at 90º with a true wind speed of 10. Then the boat starts gaining speed and the apparent wind starts changing (apparent) direction towards the bow. Now the boat is moving at a speed of 10 with a true wind 0f 10 at 90º but the apparent wind is 14 at 45º.
See previous reply about wind angle. On second thought, you're right. The AOA as measured by a 737 sensor will increase some in a downwards winds or draft compared to pitch, even when the vector is level. This might be significant if flying through a hurricane or other localized, sudden weather phenomenon with significant vertical wind speed.
The AOA isn't some magic bean thing measured at the wing. In the case of a 737 it's just a vane on the sides of the nose. The fact it measures an angle relative to the vector (vs horizon) is significant, so that the stall warning is relatively accurate (adjusted for speed) no matter if the plane is flying level or if it is ascending or descending, because you can stall a plane in any of these cases. If you are increasing the AOA/pitch too fast, you can stall the plane even while the plane is below a normal cruising pitch. You could stall a plane while the pitch is negative, even, if you were pulling too hard out of a dive, for instance.
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