Small Scale Temperature Variations in the Vicinity of NLC: Experimental and Model Results

Details Small Scale Temperature Variations in the Vicinity of NLC: Experimental and Model Results Small Scale Temperature Variations in the Vicinity of NLC: Experimental and Model Results

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sa32b05r&link_type=abstract

American Geophysical Union, Spring Meeting 2001, abstract #SA32B-05 INVITED

Physics

0300 Atmospheric Composition And Structure, 0305 Aerosols And Particles (0345, 4801), 0320 Cloud Physics And Chemistry, 0341 Middle Atmosphere, Constituent Transport And Chemistry (3334), 0350 Pressure, Density, And Temperature

Scientific paper

Gravity waves (GWs) are an ubiquitious dynamical feature of the polar summer mesopause region. To study the relation between GW-induced temperature fluctuations and NLC we have launched seven sounding rockets from the North-Norwegian island Andøya. Each of these payloads carried an ionization gauge capable to measure the total atmospheric density at a high resolution. Temperature profiles have then been determined for an altitude range between 70 and 110~km with an altitude resolution of 200~m assuming hydrostatic equilibrium. All seven temperature profiles reveal significant GW disturbances with temperature fluctuations on the order of +/-5~K between 82 and 90~km altitude. During two out of all seven cases bright NLC layers were simultaneously detected by our ground based lidar. During both flights the NLC is located in a local temperature minimum below the mesopause. It is further interesting to note that only during these two flights the phasing of the GW was such that the local temperature minimum was around 83~km, i.e. the climatological mean altitude of NLC. Hodograph analysis of falling sphere and Chaff wind measurements shows that typical horizontal wavelengths/periods of the observed GWs have been on the order of 900~km/7 hours. Triggered by these observations we have used a microphysical model of NLC generation and growth to study the interaction between GWs and NLC. Based on recently measured and modelled temperatures and water vapor mixing ratios, and our measured GW-parameters we find that the NLC-layer indeed follows the motion of the cold phase of the wave by means of a complex combination of microphysics and transport. Furthermore, we will discuss the more principal question whether GWs weaken or amplify NLC.

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