Skip to main content
Search IntMath

Sine wave in the sky over Singapore

By Murray Bourne, 23 Feb 2008

I had a friend who was heavily into gliding. He would become very excited when he observed "wave" in the sky.

Gliders (aka sailplanes) don't have engines, of course, so you spend all your time looking for lift.

[Image source: Boeing]

The lift comes from thermals (rising hot air, usually over dark-colored ground) or waves that are the result of wind blowing over mountains. When airflow is lifted by a mountain range, it is called 'orographic uplift'.

Orographic uplift wave
[Image source, from Natural History of the White-Inyo Range, Eastern California.]

So in gliding, "wave" is a standing sine curve on the leeward side of a mountain.

I saw the following wave pattern over Singapore recently. The clouds are much higher than where gliders can reach, but there is evidence of alternating rise and fall of the moist airmass. In this case, the wave could be the result of air passing over mountains in Indonesia (there are no mountains in Singapore).

sine wave in the sky
[Photo: LimPH].

See the 4 Comments below.

Leave a comment

Comment Preview

HTML: You can use simple tags like <b>, <a href="...">, etc.

To enter math, you can can either:

  1. Use simple calculator-like input in the following format (surround your math in backticks, or qq on tablet or phone):
    `a^2 = sqrt(b^2 + c^2)`
    (See more on ASCIIMath syntax); or
  2. Use simple LaTeX in the following format. Surround your math with \( and \).
    \( \int g dx = \sqrt{\frac{a}{b}} \)
    (This is standard simple LaTeX.)

NOTE: You can mix both types of math entry in your comment.


Tips, tricks, lessons, and tutoring to help reduce test anxiety and move to the top of the class.