Distribution of Lightning in different circles for different distances

Consider the cyclone eye cordinate is 15.0, 88.4. The lightning data is E:\LIGHT\a.nc

[ncid = netcdf.open(ncFilePath, 'NOWRITE');

lat = netcdf.getVar(ncid, netcdf.inqVarID(ncid, 'lat'));

lon = netcdf.getVar(ncid, netcdf.inqVarID(ncid, 'lon'));

time = netcdf.getVar(ncid, netcdf.inqVarID(ncid, 'time'));

LTNG = netcdf.getVar(ncid, netcdf.inqVarID(ncid, 'lghtn_count'));

netcdf.close(ncid);]

So I wanted an Azimuthal distribution of lightning flashes in a circle within a distance of 300 km from the cyclone eye.

Answer 1

[Shishir Reddy]

Hi Joydeb

As per my understanding, for a given data of lightning flashes, you would like to analyse the azimuthal distribution of flashes that are within a 300 km radius from the cyclone eye. I am assuming that you have latitudes, longitudes of all the lightning flashes and they are stored in ‘lat’ and ‘lon’ vectors respectively. Since I have the limited understanding of the data, here are some general steps that can be followed.

1. Distance should be calculated from cyclone eye and each lightning location.
2. Flashes that are within 300km range should be filtered out.
3. Computing the angle for these lightnings

Refer to the sample MATLAB script below for implementation of these steps:

eyeLat = 15.0;
eyeLon = 88.4;

for i = 1:length(lat)
    dLat = deg2rad(lat(i) - eyeLat);
    dLon = deg2rad(lon(i) - eyeLon);
    a = sin(dLat/2)^2 + cos(deg2rad(eyeLat)) * cos(deg2rad(lat(i))) * sin(dLon/2)^2;
    c = 2 * atan2(sqrt(a), sqrt(1-a));
    distances(i) = 6371 * c; % Earth radius in kilometers
    
    azimuths(i) = atan2(sin(dLon) * cos(deg2rad(lat(i))), ...
    cos(deg2rad(eyeLat)) * sin(deg2rad(lat(i))) -sin(deg2rad(eyeLat)) * cos(deg2rad(lat(i))) * cos(dLon));
end

withinRadius = distances <= radius;
filteredAzimuths = azimuths(withinRadius);

Finally, the results can be analysed by plotting using the ‘polarhistogram’ function.

polarhistogram(filteredAzimuths, 36); % 36 bins for each 10-degree intervals

For more information regarding ‘polarhistogram’ function, kindly refer the following documentation

https://www.mathworks.com/help/matlab/ref/polarhistogram.html

I hope this helps.