Removing Noise From Image

I have an issue where the pcolor plot has noiseness at the top part of the plot. How do I get rid of this noise and smooth the plot? I am trying to smooth and remove the noise from the image below.

This is the code I have for the plotting part of my code. I am new to MATLAB.

map = pcolor(gridLonBoundaries, gridLatBoundaries, nitrogenCellAveraged);
set(map,'edgecolor','none')
hold on
h = colorbar;
set(get(h,'label'),'string','Nitrogen Dioxide Index');
colormap jet
caxis([0.00001 0.00005])
load coast
hold on
plot(long,lat,'k')

Answer 1

[Image Analyst]

pcolor() is not the problem. The problem is in your actual data, nitrogenCellAveraged. That's what needs to be cleaned up.