Make a new document, 500x1000 pixels, white background.
Fill the selection with a "black to white" gradient starting from the top of image to the bottom like in the example.
Now go on "Filter - Render - Difference Cloud", then hit CTRL+F (Command+F on Macintosh) until you have something like this:
Now go to Image>Adjustments>Invert or just hit CTRL+I (Command+I on Mac) to invert the colors.
Now go to Image>Adjustments>Levels or hit CTRL+L (command+L on the Mac) to bring up the Levels dialogue. In the level panel magnify the white zones moving the left pointer to right and the right pointer to left. Hit OK.
Bring up the Hue/Saturation dialogue, so go to Image>Adjustments>Hue/Saturation or hit CTRL+U (Command+U on Mac). Set the values like in the example below.
Your image should look like this:
And now the final touch, go on "Filter - Brush Strokes - Angled Stroke" and set the values like in the example:
