Since this word has okurigana (hiragana attached to the kanji) you can guess that it uses the kun'yomi reading, which also happens to be a reading you didn't learn when you learned the kanji. Let's use a mnemonic for the kun'yomi reading now, though. You have to remember at least the あ part to read it.
You know that this word means to rise. Imagine something just rising on its own, like a floating tree or something. What would you say? Probably a "surprised" sound. Maybe you'd scream "あ!" when you saw this floating tree.
If you need help remembering the hiragana part, imagine that it's a girl rising up and you scream "Ah! Girl!"(あがる).
My fever is rising steadily.
Let's go up to the 3rd floor using the elevator.
Smoke is rising.