How can I calculate the percentage of clouds within each grid box i.e. 1 degree x 1 degree?

Hello everyone,

My data (clouds: 11376*270) has a spatial resolution of 5 km. It contains values: 1 (clear), 2 (probably clear), 3 (cloudy) and 4 (probably cloudy). How can I calculate the percentage/fraction of clouds within each grid box i.e. 1 degree x 1 degree (for just condition 3 (cloudy))? I want to make a figure of spatial distribution of percentage frequencies of cloudy (case 3).

My code and the figure it produces:

figure
h1=axesm('mercator', 'MapLatLimit',[15 55],'MapLonLimit',[80 150]);
 gridm;
 framem on;
mlabel on;
plabel on;
xlabel ('Spatial distribution of occurence frequencies (%) of clouds')
 tightmap;
 geoshow(h1,lat,lon,clouds,'DisplayType','texturemap')
colormap(jet(4))
labels={'Clear','P_Clear','Cloudy','P_Cloudy'};
lcolorbar(labels,'fontweight','bold');
 hold on
 coast=load('coast');
 geoshow(coast.lat, coast.long,'DisplayType','line','Color','red')

Any suggestions what I'm missing or what changes should I need to do in my code?

Kindly help.

[Image Analyst]

How many rows and columns correspond to one degree?

[IMC]

Didn't get your question.

I have data from 2 days (around 18 files/granules per day for my defined area) . And for each granule, latitude and longitude values are different. Below image shows lat values for just one granule (406 rows and 270 columns). Similarly lon and data (clouds) for one granule will also have 406*270.

Answer 1

[darova]

Here is an example using griddata

    % x y v are your data
    % create new mesh 0.1 degree in each direciton
x1 = min(x(:)):0.1:max(x(:));
y1 = min(y(:)):0.1:max(y(:));
v1 = griddata(x,y,z,x1,y1);             % interpolate data
v11 = v1*0;                             % preallocate
for i = 1:10:size(x1,1)
    for j = 1:10:size(x1,2)
        C = v1(i:i+9,j:j+9);
        v11(i:i+9,j:j+9) = sum(C(:)==3)/100;    % find '3' and sum
    end
end
pcolor(v11)

[IMC]

Thanks Darova for the solution.

But after running the above code it gives me following error at this line C = v1(i:i+9,j:j+9);

Index in position 1 exceeds array bounds (must not exceed 1).

I have used following variables in the code provided by you:

x = 4802*2401 double (longitude values)

y = 4802*2401 double (latitude values)

z = 4802*2401 double (matrix containing values 1, 2, 3,4)

x1= 1*1201 double

y1= 1*1201 double

[darova]

What are steps (degree) in your original data x and y?

[IMC]

It's actually data from geostationary satellite and had lat (y) and lon (x) as a column vector. So, I used meshgrid to create a matrix. Below is figure of latitude values (4802*2401).

[darova]

You have 0.05 degree step for lattitude. DO you know how to convert it to kilometers?

Answer 2

[Bruno Luong]

Take a look at function histcount2 and histogram2