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Rayleigh lidar detection of aerosol echoes from noctilucent cloud altitudes at the Arctic Circle
Author(s) -
Langer M.,
Müller K. P.,
Fricke K. H.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/94gl02903
Subject(s) - altitude (triangle) , lidar , aerosol , zenith , atmospheric sciences , backscatter (email) , rayleigh scattering , environmental science , solar zenith angle , atmosphere (unit) , geology , remote sensing , meteorology , physics , optics , telecommunications , mathematics , geometry , computer science , wireless
During 3 out of 16 observations runs in July and August 1993 the Rayleigh Lidar at the Andøya Rocket Range (69°N, 16°E) in Northern Norway detected aerosol echoes from noctilucent cloud altitudes on July 28, August 7, and August 9. The geometric elevation of the center of the Sun was from +1.3° to −4.5° during aerosol detection. These three events differed significantly in peak signal strength, altitude, cloud layer shape, altitude integrated signal, and temporal evolution. Aerosol echoes were seen from the altitude range 81 to 87 km. The strongest aerosol event showed a peak backscatter ratio of 240 at 83.2 km altitude equivalent to the molecular (Rayleigh) scattering signal from 41.5 km. The weakest event had a peak backscatter ratio of 7 at 84.8 km with a Rayleigh equivalent altitude of 73.3 km. The zenith optical thickness of the aerosol layers varied by approximately two orders of magnitude. Detection times ranged from longer than 5 hours to as short as 15 minutes. The temporal evolution during the events suggests that single clouds were drifting through the laser beam which has a diameter of approximately 4 m at 85 km altitude. All events occurred before local midnight and the gross temporal evolution is compatible with tidal models for the diurnal variation of the visibility in PMCs and NLCs although there is considerably more structure in the lidar data than predictable by such a model. The estimated zenith optical thickness is within the bounds of microphysical NLC models.