Plotting Eddy Kinetic Energy

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Desak Made Pera Rosita Dewi
回答： Nipun 2024-6-6
Hi I have problem with plotting eddy kinetic energy (EKE)
I have a data of sea surface height (variable name: adt) with matrix [n m k]. n is latitude, m is longitude and k is time.
I want to plot EKE with equation below
here is my initial code
regionName = 'SouthIndian' % change as you need to ..
eval(['load ' regionName]); %to evaluate the data
[n, m, k] = size(b.adt); %n =lat, m= lon, k = absolute topohraphy
adt_mean = squeeze(mean(shiftdim(b.adt,2)));
g=(9.8).^2;
f=2.*(coriolisf(b.lat)).^2;
dhx=(diff(adt_mean)./diff(b.lat)).^2;
dhy=(diff(shiftdim(adt_mean,1))./diff(b.lon)).^2;
eke=g/f*(dhx+dhy);
But it doesnt working. Plese help or any suggestion about it.
  2 个评论
Desak Made Pera Rosita Dewi
Desak Made Pera Rosita Dewi 2021-4-3
matlab said the matrix size do not match
Amilton Roberto Muhosse
Amilton Roberto Muhosse 2023-5-23
I DO NOT UNDERSTAND WHAT IS ABSOLUTE P=TOPOGRAPHY

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回答（1 个）

Nipun
Nipun 2024-6-6
Hi Desak,
I understand that you want to calculate and plot the Eddy Kinetic Energy (EKE) from sea surface height (adt) data. Based on the shared information about the code, I can confirm that the root cause of the problem is dimension handling and related calculation.
Here is the recommended version for the expected output:
regionName = 'SouthIndian'; % change as needed
eval(['load ' regionName]); % load the data
% Extract dimensions
[n, m, k] = size(b.adt); % n = lat, m = lon, k = time
% Compute the mean absolute dynamic topography (adt) over time
adt_mean = mean(b.adt, 3);
% Constants
g = (9.8)^2;
% Compute Coriolis parameter squared (f^2)
f = 2 * (coriolisf(b.lat)).^2;
% Calculate spatial derivatives
[lat_grid, lon_grid] = meshgrid(b.lat, b.lon);
dhx = (diff(adt_mean, 1, 1) ./ diff(lat_grid, 1, 1)).^2; % Gradient in lat direction
dhy = (diff(adt_mean, 1, 2) ./ diff(lon_grid, 1, 2)).^2; % Gradient in lon direction
% Extend the matrices to original size by padding with zeros
dhx = padarray(dhx, [1, 0], 'post');
dhy = padarray(dhy, [0, 1], 'post');
% Compute EKE
eke = g ./ f .* (dhx + dhy);
% Plotting EKE
figure;
imagesc(b.lon, b.lat, eke');
set(gca, 'YDir', 'normal');
colorbar;
title('Eddy Kinetic Energy (EKE)');
xlabel('Longitude');
ylabel('Latitude');
For more information on the functions used, refer to the following MathWorks documentation:
  1. "coriolisf" : https://www.mathworks.com/matlabcentral/fileexchange/47338-coriolisf
  2. "padarray" : https://www.mathworks.com/help/images/ref/padarray.html
  3. "meshgrid" : https://www.mathworks.com/help/matlab/ref/meshgrid.html
Hope this helps.
Regards,
Nipun

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