Quiver plot for Wind data of reanalysis

Question

Marzuki Marzuki 2021-11-8

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1581454-quiver-plot-for-wind-data-of-reanalysis

编辑： Cris LaPierre 2021-11-12

I plan to use Matlab to plot wind of reanalysis that I downloaded from this website: https://psl.noaa.gov/data/gridded/data.ncep.reanalysis2.pressure.html

However, the result is not as expected. I send the sample of data in this posting.

I hope the result is like the image below (run by other software).

I use the following Matlab script:

lon1=load('lon.txt');
lat1=load('lat.txt');
u=load('u.txt');
v=load('v.txt');
coast=load('world_coastline.txt');
lon1q=repmat(lon1',73,1);
lat1q=repmat(lat1,1,144);
quiver(lon1q, lat1q,u',v',1,'k','LineWidth',1)
hold on
plot(coast(:,1), coast(:,2),'k','LineWidth',1.0)
xlim([90 110]);
ylim([-8 8]);
hold off
set(gca,'TickDir','out','FontName','Times New Roman','LineWidth',1);

Hoewever, the result is strange, as given below:

I tried several combinations, and found the quiver below to give somewhat similar results (still different).

quiver(lon1q, flipud(lat1q),flipud(u'),(v')*-1,1,'k','LineWidth',1)

Result

Perhaps some of you have used quiver plots for data reanalysis, and please share your experiences. Thank you very much.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Cris LaPierre 2021-11-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1581454-quiver-plot-for-wind-data-of-reanalysis#answer_828864

编辑：Cris LaPierre 2021-11-11

在 MATLAB Online 中打开

windData.mat

Part of the issue is a mismatch between your coastline data and your quiver data. If you zoom all the way out, you will see what I mean.

load windData

[lat1q,lon1q]=meshgrid(lat1,lon1);

quiver(lon1q, lat1q,u,v,1,'k','LineWidth',1)

hold on

plot(coast(:,1), coast(:,2),'k','LineWidth',1.0)

hold off

set(gca,'TickDir','out','FontName','Times New Roman','LineWidth',1);

Use wrapTo180 on the longitudinal data to fix that.

figure

quiver(wrapTo180(lon1q), lat1q,u,v,1,'k','LineWidth',1)

hold on

plot(coast(:,1), coast(:,2),'k','LineWidth',1.0)

hold off

set(gca,'TickDir','out','FontName','Times New Roman','LineWidth',1);

If you have the Mapping Toolbox, you could do the following. To me, the coastlines look a little better.

figure

axesm('eqdcylin')%,"MapLonLimit",[90 110],"MapLatLimit",[-8 8]);

plotm(coast(:,2), coast(:,1),'k','LineWidth',1.0)

[Lon,Lat] = meshgrid(lon1,lat1);

quiverm(Lat,Lon,u',v')

I'm not sure I like the idea of arbitrarily flipping matrices to try to get an expected output. Do you have any information on how the other software processes the data? Are you sure you are using the same data in both places?

4 个评论
显示 2更早的评论隐藏 2更早的评论

Cris LaPierre 2021-11-11

在 MATLAB Online 中打开

Thank you. That is helpful information. It looks like the u and v values you have shared here are different from the ones you are using in NCL. If I download the data directly from the website, are create the quiver plot using it, I get something similar to your original plot. I have to save the variables to a mat file to upload it here.

% load data

load windData

% ncdisp('uwnd.mon.mean.nc')

% lat = double(ncread('uwnd.mon.mean.nc','lat'));

% lon = double(ncread('uwnd.mon.mean.nc','lon'));

% uU = double(ncread('uwnd.mon.mean.nc','uwnd'));

% u = squeeze(uU(:,:,1,1));

% t = double(ncread('uwnd.mon.mean.nc','time'));

% l = double(ncread("uwnd.mon.mean.nc",'level'));

%

% ncdisp('vwnd.mon.mean.nc')

% vV = double(ncread('vwnd.mon.mean.nc','vwnd'));

% v = squeeze(vV(:,:,1,1));

% Determine date of plotted data ('hours since 1800-1-1 00:00:00')

d=datetime(1800,1,1) + hours(t(1))

d = datetime

01-Jan-1979

% Determine level (millibar)

l(1)

ans = 1000

coast=load('world_coastline.txt');

% Create plot

[LN,LT] = meshgrid(lon,lat);

quiver(wrapTo180(LN),LT,u',v')

hold on

plot(coast(:,1), coast(:,2),'k','LineWidth',1.0)

hold off

xlim([90 110]);

ylim([-8 8]);

set(gca,'TickDir','out','FontName','Times New Roman','LineWidth',1);

Marzuki Marzuki 2021-11-12

Thank you @Cris LaPierre . It is really helpfull. I've checked my data, the data is the same as yours, but the data processing process is slightly different, where I replaced missing_value with NaN, for example:

ncid1 = netcdf.open('uwnd.mon.mean.nc');

varid1 = netcdf.inqVarID(ncid1,'uwnd');

v_longway = netcdf.getVar(ncid1,varid1);

missing_value = netcdf.getAtt(ncid1,varid1,'missing_value');

v_longway(v_longway==missing_value)=NaN;

v=double(v_longway(:,:,1,1));

netcdf.close(ncid1);

does this affect the results?

But it solved, thank you again.

Cris LaPierre 2021-11-12

编辑：Cris LaPierre 2021-11-12

在 MATLAB Online 中打开

No, your code returns the same result as mine. I checked using isequal. However, your code is assigning the variable v to what should be u (comes from uwnd, not vwnd).

That gave me the insight to figure out what was happening. When I check your u and v matrices, they are the same. You accidentally loaded the uwnd data for both the u and v components. That means the original quiver command was

quiver(lon1q, lat1q,u',u',1,'k','LineWidth',1)
%                      ^^

请先登录，再进行评论。

Quiver plot for Wind data of reanalysis

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

4 个评论
显示 2更早的评论隐藏 2更早的评论

更多回答（0 个）

另请参阅

类别

标签

Community Treasure Hunt

Quiver plot for Wind data of reanalysis

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

4 个评论 显示 2更早的评论隐藏 2更早的评论

更多回答（0 个）

另请参阅

类别

标签

Community Treasure Hunt

WeChat

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

4 个评论
显示 2更早的评论隐藏 2更早的评论