Noctilucent cloud observed in late April at South Pole Station: Temperature anomaly or meteoritic debris?

Observations of noctilucent clouds from Lithuania

“…These extreme cases are not alone in the NLC statistics; for example, high-latitude out-ofseason NLC observations were reported by Lohvinenko and Zalcik (1991) on 10 September 1988, from Cape Parry, Canada (70:2 3 N) and by Warren et al (1997) from the South Pole on 29 April 1992, as late as four months after summer solstice. The exact geophysical causes for these unexpected NLC formations had not been identified and still remain unclear, but these might be attributed either to the formation of unusually cold pockets of air, for instance, due to gravity wave breaking, or to large amounts of water vapor release from a Space Shuttle or large rocket launch (Stevens et al, 2005).…”

Modeling the microphysics of mesospheric ice particles: Assessment of current capabilities and basic sensitivities

“…Summertime conditions occur when the mesopause temperature minimum (near 88 km) attains a value of about 140 K or below, which occurs from about 30 days preceeding summer solstice until 70 days afterward. Although not always present, this is the domain of existence of mesospheric ice clouds, with some rather dramatic exceptions of occurrences at lower latitudes (Wickwar et al, 2002) and out of season (Warren et al, 1997). This peculiar inversion of the 'normal' seasonal cycle (cold summers and warm winters) is well known in mesospheric studies, having its origin in dynamical processes (e.g., Holton, 1982).…”

A quarter-century of satellite polar mesospheric cloud observations

“…4. There are very few reported visual sightings of NLCs in the Southern Hemisphere (SH), in part because of the limited population between 501S and 651S (see Warren et al, 1997). Thus, hemispheric differences in behavior cannot be easily identified.…”