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24

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 wind; waves generated further out in the sea (i.e. "swell waves"), which do not necessarily follow the direction of the wind. During the night, you are probably ...


11

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, and EoL Announcement for more details. So we are going to use cartopy in addition with matplotlib to plot the grib file that you have provided. Before I ...


8

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 wind is determined by the pressure gradient in isobaric coordinates the wind is determined by the geopotential gradient. The geopotential is defined by $\Phi = ...


6

This is an (annoying) artefact of BBC weather forecasts, and not an actual feature of the weather. At low wind speeds, the speed shown is the expected average speed. At higher wind speeds, the speed shown is the maximum expected gust. It changes over when the maximum expected gust is 40 mph (not knots). You can tell the difference because average wind ...


5

You need to use the following line in your model setup: COORDINATES SPHERICAL Otherwise SWAN will try to calculate wave properties on a curvilinear grid with coordinates provided in meters. In your present case, the computational area is 0.47 m x 0.24 m instead of degrees longitude and latitude.


4

Sunlight (heat), planetary rotation, and the shape of the land in passes over. Prevailing wind is mostly caused by hadley cells, or the masses of air move due to the thermal difference between the pole and the equator as well as the surface of the earth and space. Thus it is the interaction of two different thermal convection cells. this moment twists into ...


3

Wind blows from sea to land in day and land to sea in night due to pressure and temperature difference. Not so much. This is common in the Mediterranean in summer, for example, where the area sits under a stable area of high pressure and there is little wind caused by the weather system. Go to the Med in winter though, and you'll find the weather systems ...


3

I'm making my comment an answer. Waves are ubiquitous, except on land ;-). Waves in the open sea are a mix — a superposition — of waves in different directions.1 The dominating direction of large waves is, after a while, the wind direction; but that's not absolute. You have some omnidirectional background "noise" of chaotic movement as well as ...


2

Start with the original equation. Let's first write the Hydrostatic equation: $$\frac{\partial p}{\partial z}=-\rho g$$ So let's prove that $$-g=c_p\theta\frac{\partial \pi}{\partial z}$$ If we use the product rule, we observe $$-g=c_p(\frac{\partial \theta \pi}{\partial z}-\pi\frac{\partial \theta}{\partial z})$$ Since $\pi=\frac{T}{\theta}$, we can ...


2

It is not clear that the Obukhov length has an exact physical interpretation. The length L is certainly a length that dimensional argument shows to follow from the set of basis parameters that Monin and Obukhov proposed was sufficient to describe turbulence in the bottom 10% or so of atmospheric boundary layers. We may ask several questions: is the MO basis ...


2

If you assume both hydrostatic and pure geostrophic balance, that is a valid assumption. In Einstein notation, $$u_i=-\frac{1}{f \rho}\frac{\partial P}{\partial x_j}\epsilon_{ij3}$$ If we look at the equation for the streamline:$$u_i=-\frac{\partial \psi}{\partial x_j}\epsilon_{ij3}$$, then we can see that $$-\frac{\partial \psi}{\partial x_j}\epsilon_{...


1

It seems to be a thing of the past. Apparently around 2010 the 30 years calming trend reversed. Since then, wind speeds and wave heights are picking up quickly, possibly in a decadal variation pattern. Young et. al. 2010 Global Trends in Wind Speed and Wave Height Possible application for the planning of wind turbines: Zhenzhong Zeng et.al. 2019 A reversal ...


1

After looking back into this I found my error to lie in the long equation $\dfrac{\partial \pi}{\partial z}=\left(\frac{1}{p_0}\right)^{\frac{R}{c_p}}\dfrac{\partial}{\partial z}\exp\left(\frac{R}{c_p}\log(p)\right)=\left(\frac{1}{p_0}\right)^{\frac{R}{c_p}}* \frac{T}{\theta}*{\frac{R}{c_p}}*\frac{1}{p}*\dfrac{\partial p}{\partial z}$. I was wrong, ...


1

IF there has been a steady wind direction over that 24 hrs, then yes, this will give you the average wind speed. If the wind has changed direction, then there may have been higher speeds that have partially cancelled each other out.


1

Did you try to sketch one of those situations? Try a square grid, define x and y, and then put $U$ and $V$ components onto one of the grid points, which you choose as starting point. Now proceed to implement a). For example, from your starting arrows, go to the next grid point eastwards, and implement $\frac{dV}{dx}<0$, i.e. the upwards pointing arrows ...


1

I've come to a solution. I have followed @gansub's suggestion to check what there is already there, before reinventing the wheel. I found MetPy's code very (too) well structured, so the code for advection was sparse among several different functions; not so immediate to trace back and put a function together. However, GrADS brings a very nice example on how ...


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