Hot answers tagged

37 votes

Why do trees break at the same wind speed?

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 ...
user avatar
25 votes
Accepted

Why is there no middle ground between tornadoes and hurricanes?

Tornadoes are the result of small-scale effects such as the convergence of updraft/downdraft regions in a single thunderstorm, the stretching or entrainment of vertical vorticity, wind shear profiles, ...
user avatar
24 votes

Could the extraction of energy by wind turbines be harmful to the environment?

The short answer is yes, it's possible. And it can also reduce harm. Summary of the changes Here's a brief summary of the changes that happen when electricity is generated from a wind turbine, rather ...
user avatar
  • 4,060
23 votes
Accepted

Why are there waves in seas towards shore - even in night?

Ocean waves (and also in mediterranean type seas and larger lakes, but on a smaller scale) are generated by two processes: locally generated waves ("wind waves"), which follow the direction of the ...
user avatar
18 votes
Accepted

Where does wind come from?

Wind is caused by pressure differences. Think of a balloon full of air; poke a hole in it and the air comes out. Why? Because the pressure in the balloon is higher than outside, and so to regain ...
user avatar
  • 13.9k
17 votes
Accepted

Potential explanations of Red Sea crossing

To my knowledge, the best study looking at potential explanations for the Red Sea crossing is the one by Nof and Paldor (1992). They present a couple of plausible scenarios for the crossing. The main ...
user avatar
  • 14.7k
16 votes
Accepted

Why is aerodynamic resistance defined inversely?

It's partly historical, partly point-of-view, but it's not a mistake. The friction coefficient emphasises the effect of the surface on a property of the boundary layer, i.e., greater surface friction ...
user avatar
  • 3,133
14 votes
Accepted

Why does the Inter tropical Convergence Zone shift?

On a broader scale the ITCZ and monsoons are related. This is because the global circulation shifts as a result of the tilt of the earth's axis relative to the orbit around the sun. In northern ...
user avatar
13 votes
Accepted

What do quasi-geostrophic and ageostrophic mean?

Ageostrophic winds are merely the component of the actual wind that is not geostrophic. In other words, given the actual wind ($\mathbf v$) and the geostrophic wind ($\mathbf v_g$), the ageostrophic ...
user avatar
  • 13.9k
13 votes
Accepted

Plotting wind barbs in python

Your uwnd variable holds 32 bit floats and has shape (1,73,144) corresponding to time, lat, lon and is located in the Dataset ...
user avatar
  • 13.9k
13 votes
Accepted

What is the explanation of using pressure units (hPa) to express height when dealing with wind speeds?

There are several reasons. From the theoretical point of view it is beneficial to use isobaric coordinates, due to the vanishing density in the equations of motion. While in cartesian coordinates the ...
user avatar
  • 766
12 votes

What is the difference between roughness length and zero plane displacement?

First some definitions: $z_0$: Roughness length is defined as the height at which the mean velocity is zero due to substrate roughness. Real walls/ground are not smooth and often have varying degrees ...
user avatar
12 votes

What exactly is wind velocity

Before defining wind velocity, I think it is necessary to explain the continuum assumption. The basic idea is that even though gases are composed of discrete molecules occupying a small fraction of ...
user avatar
  • 14.7k
12 votes

Is this ice cover real - and what circumstances are required to make it?

Yes, it is real. Whoever took the photo, congratulations on a very fine image. I have never seen this texture on such a scale, but something similar can be achieved in the laboratory by creating a ...
user avatar
12 votes
Accepted

Do hurricanes cool the earth?

Hurricanes can be viewed as having primary and secondary circulations. The primary circulation is what we see in satellite photos, comprising the winds and clouds that circle the low pressure zone at ...
user avatar
11 votes
Accepted

Why does wind blow offshore in the morning?

The phenomenon you describe is denoted as a land breeze. It is caused by a difference between the sea surface temperature and the land surface temperature. Surface Temperature During day time the ...
user avatar
10 votes
Accepted

What exactly is wind velocity

You can calibrate anemometers from other anemometers, or loosely from a windsock if precision isn't that important. But per your question, how was the first anemometer calibrated? See my answer ...
user avatar
  • 13.9k
10 votes
Accepted

Winds in a northern hemisphere hurricane

The winds in a hurricane move cyclonic and inward at the surface and anti-cyclonic and outward in the upper troposphere. Cyclonic winds are counter-clockwise in the northern hemisphere and clockwise ...
user avatar
  • 13.9k
10 votes

Why is aerodynamic resistance defined inversely?

This is a good question, and the answer is, aerodynamic resistance is not defined inversely. It is rather, defined in a context that is often misinterpreted. In your question, you state that ...
user avatar
  • 4,925
10 votes

Why is ocean surface velocity around 3% of wind velocity?

A very good analysis looking at the 3% relationship is an article by Weber (1983). His main result is that: We assume a fully developed sea, and take the eddy viscosity to be proportional to the ...
user avatar
  • 14.7k
10 votes
Accepted

Wind profile below the aerodynamic roughness length

The key text here is "for $z>z_0$". It's telling you that, while you can evaluate the equation for other values of $z$, outside of that range the equation is not a valid description of the ...
user avatar
  • 3,133
10 votes
Accepted

How to calculate w-wind?

Omega, ω is closely related to w in meteorology. It can be moved towards w using the chain (this reminder from Watkins at SJSU helped)... ...
user avatar
10 votes

How do these cloud forms grow?

Looks like Cirrus Fibratus (Ci fib) to me. See e.g. Wolkenatlas or Clouds Online. Regarding the formation of Ci fib, Name of Clouds says: Cirrus fibratus clouds are formed when winds at high ...
user avatar
10 votes
Accepted

Plotting ERA5 U/V Wind Data Using Python

First off very few people are using Basemap from Matplotlib these days. From this link matplot basemap Basemap is deprecated in favor of the Cartopy project. See notes in Cartopy, New Management, ...
user avatar
  • 6,208
9 votes

Does "wind" include the air molecules involved, or merely the kinetic energy?

Kinetic energy is the work needed to accelerate a mass. Wind defined as the velocity air (not the same as energy, as noted in comment). However, the air moved by wind is a good example of kinetic ...
user avatar
  • 5,896
9 votes
Accepted

Why do certain areas on Earth have a higher or lower air pressure at sea level?

By way of analogy consider a hot air balloon. The balloon encloses some air. As the air is heated, via massive gas burners, the air in the balloon becomes less dense compared to the air outside the ...
user avatar
  • 20.3k
9 votes

Is this ice cover real - and what circumstances are required to make it?

This picture was taken in what seem to be a small pond, of very calm water. It seem that in ideal conditions, implying but not limited to : absence of winds clean water eg: no nuclei to provide an ...
user avatar
  • 2,623
9 votes
Accepted

Long-term Wind Speed Forecasting: reality or wishful thinking?

Warning: "long-term wind-speed forecasting for generation" has (at least) two very different meanings. One refers to forecasting a distribution of wind speeds; the other refers to hour-by-hour (or ...
user avatar
  • 4,060
9 votes

Why do trees break at the same wind speed?

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 ...
user avatar
8 votes
Accepted

How can odor travel be tracked

The first problem to tackle is "what is an odor"? An odor is a chemical aerosol or gas, which are small molecules suspended in the atmosphere. To track the odors of pizza or burning wood you would ...
user avatar
  • 13.9k

Only top scored, non community-wiki answers of a minimum length are eligible