In the summertime in the far northern or southern latitudes, high in the Earth’s atmosphere at the edge of space, thin, silvery clouds sometimes become visible just after sunset. These high clouds, occurring at altitudes of about 80 kilometers (50 miles), are called polar mesospheric clouds (PMCs). They are also called noctilucent (“night-shining”) clouds. In recent years, polar mesospheric clouds seem to be occurring more frequently and at lower latitudes than they have in the past, and studies are underway to determine whether their occurrence is related to global climate change.
|
THEMEN
Foto
