Mesospheric clouds and the duality of gravity waves Journal Article

Overview

Mesospheric clouds, also known as noctilucent clouds and polar mesospheric clouds, are the highest clouds in the Earth's atmosphere. They occur at an average altitude of 83 km, approximately ten times higher than cirrus clouds, in the atmospheric region known as the mesosphere. At most a few kilometers thick, mesospheric clouds are comprised of ice water and generally form in the Northern and Southern Hemisphere polar regions during their respective summer months—typically from about 3–5 weeks before summer solstice to 7–9 weeks afterward. Ground‐based observations indicate that the occurrence frequency of mesospheric clouds has been increasing over the past ∼100 years. In addition, mesospheric cloud displays have been observed as far equatorward as 42° in the summers of 1999, 2000, and 2001 over the Rocky Mountain states.