然而，这种纯粹的视觉系统在恶劣天气下毫无用处，到了20世纪30年代，无线电通信开始用于空中交通管制。
However, this purely visual system was useless in bad weather, and, by the 1930s, radio communication was coming into use for ATC.
船只可以在恶劣天气下也避开已知的冰山和曲折的海岸线。
Ships can avoid known icebergs or hazardous shorelines even in the roughest of weather.
时刻我们都有帐篷或直升机在手边以备在恶劣天气下做庇护之用。
There will be always a tent or helicopter close at hand to take shelter in from the adverse weather.
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