There is no rule for this, specifically.
The following two rules generally apply to long and high jumps:
Long Jumps can move a distance up to your Strength Score. (DC10 to clear a 1/4 length obstacle)
High Jumps can move a distance up to 3 + your strength modifier.
I propose the following house rule ideas.
- You can just travel one quarter of the height distance as a part of the jump. (jump 4 feet high, move 1 foot over)
- Increase the difficulty of the check during a long jump to jump higher. (Maybe DC20 to clear 1/2 the distance as height?)
- Calculate the difference in ballistic trajectory between your high-jump and long-jump abilities. (see Notes*)
Ultimately, this shouldn't come up a lot, so you should work with your GM to find the solution that works best for you and your game. Keep in mind that distance jumped counts as distance traveled. If you have a speed of 30, you can't run 20 feet and jump 11 feet.
Notes on Calculation*:
With a Strength of 20, you can travel 20 horizontal feet or 8 vertical feet. With a Strength of 10, you can travel 10 horizontal feet or 3 vertical feet. It can be said that each foot available of vertical jump (V) is a function of available horizontal feet (H).
V = 3 + (H-10)/2
So, with 20 feet available, jumping 10 feet horizontally leaves me 3 feet of available vertical movement.
PS - Just to be complicated, you could also take the percentage of jump you used and allow the remaining percentage to be applied to the other axis (horizontal vs vertical); jumping 75% of 20 feet, allows you to jump 25% of 8 feet and vice versa.