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37

Why do trees break at the same wind speed? Image source: Wikimedia Commons Note that in the above image, that almost all of the trees had their tops snapped off. This claim is about tree's being snapped in two and is not about trees falling over or being uprooted. This claim is approximately valid for many species of trees. Apparently oaks can withstand ...


9

As the other answer points out, this is very likely an evolutionary adaptation that balances sturdiness with unnecessary overengineering. From a physics perspective, the relatively constant breaking strength of a tree is related to allometry, which is the relationship among the tree's proportions as it grows. A young tree is short and thin, with relatively ...


8

The general claim seems to be incorrect: This phenomenon is independent of type and size of the tree. Based on other answers, the claims around this appear to be that the scale of the tree doesn't matter. For example the sciencemag.org article referenced in David Hammon's answer talks about experiments around different thicknesses of wood: As one might ...


5

Some excellent answers are already available, but they are all examining a single tree in isolation, as if putting a tree to a wind tunnel to see whether it snaps or not. That's not how every trees species handles winds. At the latitudes I'm used to, which is the temperate climate of Europe, the fastest winds blow over elevated terrain which is often ...


3

One important additional factor is that the stress (and damage) isn't linear. A very basic idea is that energy is velocity squared. But Prahl et. al. 2008 included some review of the theories on damage from winds and the two typical theories: wind loads, which are approximately proportional to the exerted pressure and, hence, to the square of the wind ...


3

I think you’re mixing up frames of reference a bit here. That ~400 m/s speed of the surface is relative to an absolute, non-rotating frame of reference in which an observer sees the Earth as spinning on its axis. In meteorology we typically use a rotating frame of reference that spins with the Earth, in which an observer sees the surface as moving at 0 m/s....


2

Like many of the other questions I answer on Earth Science SE, the answer is complicated. Based on the principle of geostrophy, the Coriolis force will point to the right of the wind vector in the northern hemisphere (left in the southern hemisphere). Can you validate the Coriolis force based on the wind rose? No. You would need multiple simultaneous wind ...


2

Well, the variable PBLH should tell you the PBL height. If you want the level that the PBL is, I suggest modifying the Registry.EM_COMMON file. Perhaps I can refer you to WRF-Python to help you with your calculation. For example, wrf.interplevel might be the function to use to interpolate to the PBL height. If you interpolate to fractions of the PBL height, ...


2

Air is affected by friction. A brief search of AMS journals shows over 14,000 times friction is mentioned. How it is manifested in the equations that describe the atmosphere is complicated. Let's think of wind as 'air moving' or perhaps space moving which air occupies. At some point, called the roughness length, the wind is 0 m/s (or knots or mph). If such a ...


2

An answer I got on Reddit which seems to make sense is that fronts are usually accompanied by a pressure change which locally reinforces the "normal" geostrophic wind which changes the wind direction. If anyone has a more in depth answer I'd love to hear it.


2

The wind varies with height (speed and direction) so the measurement will depend on the flight height of the drones. It is best to have a lidar or sodar equipment for 3D wind measurement, but they are expensive (they can measure more than 150 m). Another alternative is to install a meteorological tower with wind measurements at different heights. Obviously, ...


1

All weather agencies record ‘ambient temperature’— how warm the air is in the shade and sheltered from the wind. This is done by placing weather recording instruments in a Stevenson Screen. The height above ground that Stevenson Screens are placed is between 1.25 and 2 m (4 ft 1 in and 6 ft 7 in). By using this approach weather readings from around the world ...


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