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I have been fascinated with the wind animation that I have seen on sites like Zoom earth. What is the "thickness" of the air stream that the animation represents. How far from the surface is this information accurate?

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The data that you are seeing is the wind speed the models predict at 10m above the 'model surface'. 10m is the standardised height at which wind is measured, as defined by the World Meteorological Organization. There is no 'thickness' to the data shown. On other websites that give you more direct access to the data, you can look at wind speed predictions for a number of different 'pressure surfaces' as well as the 10m-above-the-surface surface.

On Zoom Earth, you can see winds speeds are much higher over sea than land. This is a good indication of low altitude winds, which you can look for on other websites too if you are uncertain what wind data are shown. This is due to the friction of the land surface. As you increase in height this effects drops off quickly, except perhaps in mountainous areas.

Earlier, I referred to the 'model surface'. Here's an explanation of how that this different to the actual Earth's surface and it's consequences to the modelling: Model resolutions vary but each grid point typically covers somewhere between a 2×2km² to a 30×30km² square. Each grid point is given a single height measurement, which is the average height of the model grid square. This results in a smoothing of the modelled Earth's surface; sharp peaks and valley are missed. This smoothing affects the behaviour of the modelled wind and the height at which it may actually be experienced. Out at sea, the smoothing is not a consideration and there is physically less friction so wind modelling tends to be more accurate.

Here is an embarrassingly rough sketch showing this graphically. The data you are looking at is the wind speed the model predicts along the blue line.

Image tries to show how topography is smoothed in a weather model and that the wind shown in Zoom is 10m above this surface.

A note on models on Zoom Earth: Zoom says it uses data from the GFS and ICON models. GFS has a resolution of 27km, so there will be strong smoothing. The various ICON models use 2.2km, 7km, and 13km resolutions. I don't know which ICON model Zoom Earth gets its data from.

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  • $\begingroup$ Thanks for all the information. Great answer. $\endgroup$ Commented Dec 4, 2022 at 15:07

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