Simultaneous Observation of Temperatures and ice Particles in the mid-latitude (54 N) Mesopause Region

Details Simultaneous Observation of Temperatures and ice Particles in the mid-latitude (54 N) Mesopause Region Simultaneous Observation of Temperatures and ice Particles in the mid-latitude (54 N) Mesopause Region

Dec 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmsa13a0230g&link_type=abstract

American Geophysical Union, Fall Meeting 2005, abstract #SA13A-0230

Computer Science

Sound

0305 Aerosols And Particles (0345, 4801, 4906), 0341 Middle Atmosphere: Constituent Transport And Chemistry (3334), 3332 Mesospheric Dynamics, 3360 Remote Sensing

Scientific paper

Meteoric dust in the mesopause region is expected to form the condensation nuclei of ice clouds with particle radii of up to tens of nanometers. These ice particles are responsible for strong echos in radar and lidar signals, known as Mesospheric Summer Echos (MSE) and Noctilucent Clouds (NLC), respectively. Though MSE and NLC are mainly a phenomenon of the summer mesopause at polar regions, we will present observations of NLC and MSE from the mid-latitude location of Kuehlungsborn (54°N, 12°E). Since 1997 up to five NLC per year have been observed by lidar (overall observation probability up to 10%), showing that the atmospheric conditions for NLC are fulfilled only occassionally at this location. Despite this small occurrence rate of NLC, there is an obvious interannual variation with a minimum during the years 2000 and 2002. Since 2003 the NLC occurrence rate is increasing again, allowing lidar observations at up to four different wavelengths (770 nm, 589 nm, 532 nm, and 355 nm). With the assumption of a mono-modal, log-normal particle size distribution we derived mode radii between 25 and 60 nm and particle densities between 50 and 400 cm-1. This is well within the range of parameters observed at more polar locations. The combination of Rayleigh and potassium resonance lidar additionally enables temperatures measurements in the mesosphere and lower thermosphere. The average night mean mesopause temperatures during the summers 2003 to 2005 were observed to be about 150 K at 87 km, therefore a few Kelvin warmer than the frost point temperature. But typically the temperature profiles are disturbed by tidal and gravity waves with amplitudes of up to ±20 K. Direct temperature measurements within the NLC are inhibited by observational constraints, while observations just below and above the NLC indicate temperatures below the frost point. Additionally, daytime temperature profiles have been observed by the potassium lidar even within MSE. These soundings directly show ice supersaturation within the ice layer. But the only small supersaturation give reason for the assumption that typically the nucleation process has taken place at other locations and the ice layer has been advected to our site.

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