What does 上空 mean?
上空 is a Japanese noun meaning “sky, high-altitude sky, upper air” in English. It is written as 上空 in kanji, じょうくう in hiragana, and joukuu in romaji. This word is part of JLPT N1 vocabulary.
Example sentence
寒波が日本の上空を通過したのです。
A cold wave passed over Japan.