凌云 is mostly literary. You will meet it in set phrases like 凌云壮志 (línɡyún zhuànɡzhì, "sky-high ambitions") or 壮志凌云 rather than in everyday speech. The core image is always "rising above the clouds".
memory
凌 = "to rise above / overtop" + 云 = "clouds". Picture a person or tower literally poking through the cloud layer — that is the mental image behind every use of 凌云.
