Rough surface when printing
I have experienced this problem.  This picture is one that I could have taken. 

It has always been because I was putting too much plastic into the available space.

This has been caused two things: overextrusion -- squirting out too much plastic for the intended layer height, and the bed being too "high" so that the gap between the nozzle and the bed is too thin.

In both cases, too much plastic is trying to be placed in too small a volume.  The plastic has to go somewhere, and ripples follow.  Because the nozzle rubs against the adjacent lines which have already been deposited, an up-bump pushes up the nozzle on the line beside the bump, and a coherent pattern of ripples can form.

The "bump up" is a real effect from the elasticity of the Z-axis, including all the resulting strains of twisting and lifting the nozzle.