Noctilucent Clouds Over Northern Italy
October 13, 2021
Photographer: Paolo Bardelli
Summary Author: Paolo Bardelli; Cadan Cummings
The photo above shows a view of noctilucent clouds observed over Albusciago, Italy in June 2021. Noctilucent clouds, also referred to as night-shining clouds or NLCs, are the highest altitude clouds in Earth’s atmosphere (approximately 50 miles / 83 km) and are usually only visible in the 75 minutes to 2.5 hours before sunrise or after sunset. These unique clouds form when water vapor aggregates around specks of debris and meteorite dust in the mesosphere and freezes to form tiny ice crystals. NLC viewing mostly occurs for a few weeks around the summer solstice in each hemisphere and are confined to mid-to-higher latitudes. Historically, this region starts around 50 degrees north or south latitudes and extends as far as the polar circles. However in recent years, possibly due to climate change, the noctilucent clouds have appeared further outside this typical area. This southern growth was evident on this evening in June when they literally filled the sky of northern Italy (45° N latitude), the largest ever apparition in our area. The next morning the clouds were moving north, still remaining clearly visible in the colors of dawn.