じょうくう上空joukuu
1.

The region of the atmosphere that is situated directly above a specific location, characterized by its elevation and often devoid of clouds.

2.

The area of the sky that is perceived to be at a great height, commonly associated with expansive views and clear weather conditions.

3.

The uppermost layer of the air surrounding the Earth, typically referenced in relation to weather patterns or aviation.

Example:

寒波が日本の上空を通過したのです。

しじょうくうぜん史上空前shijoukuuzen
1.

A phrase used to describe an event or phenomenon that has never happened before throughout history, signifying its unique and exceptional nature.

2.

Characterizing a significant occurrence that stands out as extraordinary and without precedent, often leading to a transformative change in society or culture.

3.

Denoting a remarkable situation or achievement that is unparalleled and brings about considerable attention or impact, marking a pivotal moment in history.