How to plot fewer arrows and increase their size on a quiver plot that is merged over another field?

I am merging 3 fields together (land/ocean, pressure field and velocity field).

I manage to align all the fields together but I can't find a way to reduce the number of arrows I am plotting on my quiver plot. I also want to increase the size of my arrows. When I tried to plot only 1/4 of the quiver's arrows, the quiver plot disappeared. See the commented line above.

I have attached my data as "data2.mat".

Here is my code:

load('data2.mat');

figure(1)

ax1 = axes;
pcolor(Land);
axis ij;
axis equal;
box on;
axis off;
shading flat;

ax2 = axes;
hold on;
pcolor(XERAmat,YERAmat, mslpPosMask);
contour(XERAmat,YERAmat, mslpPosMask,'k','LevelList',...
    min(mslpPosMask,[],'all') - rem(min(mslpPosMask,[],'all'),1):1:...
    max(mslpPosMask,[],'all') + (1 - rem(max(mslpPosMask,[],'all'),1)),'ShowText','on');
axis ij;
axis equal;
box on;
axis off;
shading flat;

ax3 = axes;
id = 4 ;  % plot every 4th value 
h2 = quiver(Upos,Vpos,'k');
%I try to plot fewers arrows and increase the size of the arrows
%h2 = quiver(Upos(1:id:end,1:id:end),Vpos(1:id:end,1:id:end),'k');
set(h2,'AutoScale','on', 'AutoScaleFactor', 5)
axis ij;
axis equal;
box on;
axis off;
shading flat;

%%Link axes together
linkaxes([ax1,ax2,ax3])

%%Hide the top axes
ax2.Visible = 'off';
ax2.XTick = [];
ax2.YTick = [];

%%Give each one its own colormap
colormap(ax1,cmap)
colormap(ax2,'parula')

%%Then add colorbars and get everything lined up
cb2 = colorbar(ax2,'Position',[0.8 0.11 0.05 0.815]);
ylabel(cb2,'sea level pressure (hPa)','Fontsize',18); 
xlim([110 270]);
ylim([70 260]);

My actual figure:

I want my quiver plot to look more something like this:

Thank you

Answer 1

[MJFcoNaN]

You may try this code:

id = 8 ;  % plot every 4th value 
ScaleFactor = 10;

Upos0 = Upos;
Vpos0 = Vpos;
Upos = NaN(size(Upos0));
Vpos = NaN(size(Vpos0));

Upos(1:id:end, 1:id:end)=Upos0(1:id:end, 1:id:end);
Vpos(1:id:end, 1:id:end)=Vpos0(1:id:end, 1:id:end);

h2 = quiver(Upos,Vpos,'k');
%I try to plot fewers arrows and increase the size of the arrows
%h2 = quiver(Upos(1:id:end,1:id:end),Vpos(1:id:end,1:id:end),'k');
set(h2,'AutoScale','on', 'AutoScaleFactor', ScaleFactor)

[A LL]

It does plot fewer arrows, but it displays the arrow in a very weird way making lines of arrows. I want my vector field to look like the second figure I have attached to my question.

Here is what I get with the code you proposed:

[MJFcoNaN]

Sorry I forgot a comma...It should be:

Upos(1:id:end, 1:id:end)=Upos0(1:id:end, 1:id:end);
Vpos(1:id:end, 1:id:end)=Vpos0(1:id:end, 1:id:end);

[A LL]

I ended up converting everthing on a lat/lon grid and using quivermc instead of quiver. Thank you for your time.