Talk:Atmospheric tide
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Fourier Analysis - obviously nonsense
[edit]The main section explains the 12 hour component of atmoshperic thermal tides by stating that a fundamental with 24hr period is a squarewave and is rich in harmonics. This, it is said, creates a 2nd harmonic with a period of 12hrs. However, most schoolboys know that a square wave has odd harmonics only, so this cannot be a valid explanation for a component at 12hrs. Moreover, this reference describes a 12hr period only:-
http://weather.mailasail.com/Franks-Weather/Atmospheric-Tides
with no mention of a 24hr component. Could comeone clarify this, and remove the reference to the 2nd harmonic of a squarewave, which is obvious nonsense that almost anyone will recognise as such. --82.32.49.157 (talk) 18:35, 13 March 2011 (UTC)
Agreed: a square wave representation of the day-night cycle of solar heating would have no semidiurnal (twice a day) harmonic, or any other odd harmonics. I think this mistake could be fixed by simply replacing "square wave" with "rectified sine wave" in the text. A rectified sine wave is a better approximating to the solar heating function than a square wave, and it has both odd and even harmonics. Of course the text should also note that the diurnal (once a day) harmonic is the primary component of the forcing.128.115.184.106 (talk) 21:44, 30 December 2013 (UTC)Curt Covey, PCMDI / LLNL
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Side view
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A diagram showing the Earth from the side and how the shape of the atmosphere varies would be very helpful. -- Beland (talk) 19:00, 12 September 2019 (UTC)
Amplitudes 60 and 120 hPa, or just Pa?
[edit]The current article text contains:
"The fundamental solar diurnal tidal mode which optimally matches the solar heat input configuration and thus is most strongly excited is the Hough mode (1, −2) (Figure 3). It depends on local time and travels westward with the Sun. It is an external mode of class 2 and has the eigenvalue of ε 1
−2 = −12.56. Its maximum pressure amplitude on the ground is about 60 hPa.[1] The largest solar semidiurnal wave is mode (2, 2) with maximum pressure amplitudes at the ground of 120 hPa. It is an internal class 1 wave. Its amplitude increases exponentially with altitude. Although its solar excitation is half of that of mode (1, −2), its amplitude on the ground is larger by a factor of two. This indicates the effect of suppression of external waves, in this case by a factor of four.[2]"
I have no access to the source mentioned.
- But in https://journals.ametsoc.org/view/journals/atsc/68/3/2010jas3560.1.xml I see mention of measurements revealing amplitudes on the order of 100 Pa for semidiurnal atmospheric tidal waves in Jakarta, Indonesia (formerly Batavia).
- And on https://www.buienradar.nl/nederland/weerbericht/weergrafieken/6290 [Meetstation Twente, 2022:03021] I see an earth surface atmospheric pressure graph showing what may be a semidiurnal tidal wave with an amplitude of approximately 100 Pa as well in Enschede, the Netherlands.
Therefore, and since 100 hPa is equivalent to no less than approximately 10% of the average atmospheric pressure at sea level of around 1,013.25 hPa (only the strongest hurricanes reach surface pressures less than 900 hPa), I wonder if the amplitudes 60 hPa and 120 hPa mentioned in the article are actually meant as 60 Pa and 120 Pa.Redav (talk) 01:47, 22 March 2022 (UTC)