Calculating u and v components from wind direction and speed

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Shai Katz 2022-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/1699985-calculating-u-and-v-components-from-wind-direction-and-speed

编辑： KSSV 2024-7-11

采纳的回答： Les Beckham

Hi,

I would like to plot a wind filed on a map.

I have lat vector, lon vector, wind speed vector and wind direction vector.

As far as I understand the simplest way is to use quiverm or quiver (but quiver can't plot over a map).

To use both function I need the u and v components, and I don't have them, and I don't have the angle for the cos and sin functions in these formulas.

How can calculate them? converting wind direction to math degrees (in a formula) isn't straight forward.

Appricate your help for the easiest way.

Thank you!

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Answer 1

Les Beckham 2022-4-19

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编辑：Les Beckham 2022-4-19

在 MATLAB Online 中打开

Actually, it is straightforward.

v (North (y) component) and u (East (x) component) can be calculated from S (wind speed) and D (direction) as follows

S = 10; % example - replace with your data

D = 30; % example, wind coming from the North-northeast

D = 270 - D; % convert wind direction to Matlab graphics coordinate convention

u = S*cosd(D);

v = S*sind(D);

quiver(0,0,u,v)

axis equal

xlim([-10 10])

ylim([-10 10])

grid on

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Les Beckham 2022-4-21

编辑：Les Beckham 2022-4-21

在 MATLAB Online 中打开

Sorry for the delayed response. I got busy with real life.

It appears that this is working as expected.

lon_00Z_november19 = [35.1123 35.0964 34.9594 34.8815 35.0548 35.0208 35.2217 35.1973 34.9616 35.1784 35.1233 34.9546];

lat_00Z_november19 = [32.8466 32.6028 32.6808 32.4732 32.8034 32.7611 31.7806 31.7704 31.8341 32.7078 31.6644 32.5724];

wind_direction_00Z_november19 = [90 70 80 80 120 77 100 90 100 70 100 80];

wind_speed_00Z_november19 = [3.0000 12.0000 7.5000 3.5000 5.0000 13.1000 4.0000 6.5000 9.5000 5.5000 9.5000 9.5000];

S = wind_speed_00Z_november19;

D = 270 - wind_direction_00Z_november19;

u = S.*cosd(D);

v = S.*sind(D);

quiver(lat_00Z_november19, lon_00Z_november19, u, v)

axis equal % perhaps you were missing this? Without it the angles won't look right

grid on

text(lat_00Z_november19, lon_00Z_november19, split(num2str(wind_direction_00Z_november19)))

Here is what it looks like if you don't have the axis equal command. The angles don't look right at all.

I'm not sure how this translates to the quiverm command since I can't experiment with that.

figure

quiver(lat_00Z_november19, lon_00Z_november19, u, v)

grid on

text(lat_00Z_november19, lon_00Z_november19, split(num2str(wind_direction_00Z_november19)))

Shai Katz 2022-4-22

Thank you very much for you help, it works!

Do you know how can I plot them on geographic map? no just on a blank grid? I guess and need somehow to use the quiverm function..

Les Beckham 2022-4-22

You are welcome.

Would you mind accepting the answer then?

Unfortunately, I don't have the mapping toolbox so I'm not going to be much help with that. Looking at the online doc, though, it looks pretty similar to quiver. You will probably need to play around with the scale argument to quiverm (using this syntax: h = quiverm(lat,lon,deltalat,deltalon,scale)) to use your u and v speed components as the deltalat and deltalon arguments.

Good luck.

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Answer 2

Tala 2022-4-19

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编辑：Tala 2022-4-19

在 MATLAB Online 中打开

I have done similar tasks before. If you have experimental data, your sensor should generate two time histories; velocity (Mag) and direction (Dir) with identical length, depending on your smapling frequency. To th ebest of knowledge, no sensor can read in 3D, you need to rotate your sensor if you want Z direction measurments.

You are right, direction could be tricky because small changes in wind direction could cause significant changes in the probe's reading. In other words, your probe could read between 350 and 10 degrees but in reallity these are all similar values. You need to be strategic about placing your probe at the right angle. If you avarage it out you get 180, completely opposite angle! The graph below shoes the issue:

I could not find the code that I used before, but I did something like this:

% truncating the first and last few data points 
%nn=  number of points you wanna truncate from the beginning 
%mm=  number of points you wanna truncate from the end 
Vx=sum((Mag(nn:mm)).*cosd((Dir(nn:mm))))/(mm-nn+1); %V(i).cos(theta(i))/n
Vy=sum((Mag(nn:mm)).*sind((Dir(nn:mm))))/(mm-nn+1);
angle=atand(Vy/Vx);
% now you need to create a x y z domain (in your case lat lon height)
% Vz=0 in this case
quiver3(x,y,z,Vx,Vy,0);

Below is the plot I got from my experiments back in the day. I measured the wiind speed around buildings at 3 different heights.

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Answer 3

BHUKYA SAMA 2023-9-17

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i have matrix V(lat,lon,level,time) how to do dV/dZ, can i use gradient (V)/gradient (Z) ?

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Answer 4

BHUKYA SAMA 2023-9-17

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https://ww2.mathworks.cn/matlabcentral/answers/1699985-calculating-u-and-v-components-from-wind-direction-and-speed#answer_1312042

编辑：KSSV 2024-7-11

在 MATLAB Online 中打开

i am need to ccalculate the dV/dZ from era5, below code is okay?

clear all
close all
fclose all
load era5_all_level_parametrs_2015_04_04.mat
%%%%%%%% Hlecity %%%%%%%%%55
u_wind_avg=0.5*(u1(1,1,26,1)-u1(1,1,37,1));%u(lon,lat,level,time)
v_wind_avg=0.5*(v1(1,1,26,1)-v1(1,1,37,1));%v(lon,lat,level,time)
for i=1:37
    p0=1000;
    ht(i)=8*log(level1(i)/p0);
end
ht1=-ht;
ht2=ht1*1000;
% du_dz=gradient(u1(:,:,26:end,:))/(ht2(26)-ht2(end));
% dv_dz=gradient(v1(:,:,26:end,:))/(ht2(26)-ht2(end));
du_dz=gradient(u1(1,1:2,26:end,1));
dv_dz=gradient(v1(1,1,26:end,1));

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Calculating u and v components from wind direction and speed

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