Tidal Effects on Atmosphere

In summary, there is a tidal swell or circulatory effect in the atmosphere caused by the moon's gravity, but it is very small and not the dominant driving force. It can be detected through Fourier analysis of barometric pressure measurements over the course of a year, with its frequency response matching that of the solar day rather than the lunar day. This is because the atmospheric tides are primarily driven by solar radiation, but the lunar contribution is still present. To observe this effect yourself, you can analyze barometric pressure data and look for peaks corresponding to lunar and solar frequencies.
  • #1
Nidum
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I there a tidal swell or circulatory effect in the atmosphere caused by the moons gravity ?
 
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That's a great question. I think the easiest way to detect it would be to take a Fourier transform of a barometric pressure measurement over the course of a year or so and see of all the well-known tidal frequencies are present. I bet they are. See:

https://en.wikipedia.org/wiki/Theory_of_tides
 
  • #3
Nidum said:
Is there a tidal swell or circulatory effect in the atmosphere caused by the moons gravity ?
Yes, but it's very small.

People have been measuring barometric pressure around the world for hundreds of years, so there's lots of data to see tidal signatures in those readings. And they certainly are present. Surprisingly, people found the frequency response to match that of the solar day rather than the lunar day. It took quite a while to see that there was a lunar contribution; it's about 1/20th of that from the Sun. That's inconsistent with a gravitationally driven tides.

The solar atmospheric tides are driven primarily by sunlight, and primarily by absorption of ultraviolet by ozone in the stratosphere and absorption of visible and infrared by water vapor in the troposphere. The lunar atmospheric tides apparently are gravitational.
 
  • #4
D H said:
Surprisingly, people found the frequency response to match that of the solar day rather than the lunar day. It took quite a while to see that there was a lunar contribution; it's about 1/20th of that from the Sun. That's inconsistent with a gravitationally driven tides.

The atmospheric tides are not dominated by gravitational driving, but they are gravitationally driven. It's just that the solar radiation driving produces a larger effect.

This is easy to distinguish with Fourier analysis, because of the varying driving frequencies and phases. In a single year of data, it is not hard to pick out driving forces that are only 1-2% of the dominant ones. Looking in the time domain is a weak technique for effects that are most easily discerned in the frequency domain.

To see this effect for yourself, download a reasonably accurate barometric pressure sampled every 15 minutes or so for a whole year and compute the Fourier transform. The largest amplitude is the solar heating term, with a frequency of 1.000 (in units of 1/day). But you will also see the lunar diurnal and semidiurnal peaks also, as well as the solar semidiurnal with a frequency of 2.000. These peaks are evidence of gravitational driving.
 
  • #5
Dr. Courtney said:
The largest amplitude is the solar heating term, with a frequency of 1.000 (in units of 1/day). But you will also see the lunar diurnal and semidiurnal peaks also, as well as the solar semidiurnal with a frequency of 2.000. These peaks are evidence of gravitational driving.
The largest is the solar semidiurnal, not the solar diurnal. It's primarily a heating effect. For more, see chapter 9 of the lecture notes of the MIT OpenCourseWare "Dynamics of the Atmosphere" at http://ocw.mit.edu/courses/earth-at...-of-the-atmosphere-spring-2008/lecture-notes/
 
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What are tidal effects on the atmosphere?

Tidal effects on the atmosphere refer to the changes in air pressure, temperature, and wind patterns caused by the gravitational pull of the moon and sun on the Earth's atmosphere.

How do tides affect the atmosphere?

Tides affect the atmosphere by causing the air to move vertically and horizontally, which can result in changes in air pressure. They can also influence the formation of clouds and precipitation, as well as impact wind patterns.

What is the primary cause of tidal effects on the atmosphere?

The primary cause of tidal effects on the atmosphere is the gravitational pull of the moon and sun on the Earth. The moon's gravitational pull is stronger due to its proximity to the Earth, while the sun's pull is weaker but still significant.

Why do tides have a greater impact on coastal regions compared to inland areas?

Tides have a greater impact on coastal regions because the ocean's water is directly affected by the gravitational pull of the moon and sun. This causes a rise and fall in sea level, which can also affect the air pressure and wind patterns in these areas.

What are some potential consequences of tidal effects on the atmosphere?

Some potential consequences of tidal effects on the atmosphere include changes in weather patterns, such as more frequent storms or droughts, as well as impacts on coastal erosion and sea level rise. They can also affect marine ecosystems and human activities, such as fishing and shipping.

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