Science Seminars

2/18/2010 – Active and passive remote sensing of the Mesopause region: What do we learn from observing NoctiLucent Clouds (NLC)

Speaker: Gerd Baumgarten, Leibniz-Institute of Atmospheric Physics, University of Rostock, Germany
Date: Thursday, Feb 18, 2010
Time: 4:00pm
Location: Duane D142

Seminar Abstract:

Active remote sensing by lidar allows to study processes in the middle atmosphere from small (<1km, 5min) to medium scales (6h) and deliver reliable observations to investigate year to year fluctuations of the atmosphere. Due to the rather complicated instrumental setup only a few lidars are capable of sounding the mesosphere. Especially the polar summer mesopause region offers astonishing processes, e.g. the mean temperature is more than 60K below radiative equilibrium, although the sun is permanently above the horizon. NLC, forming in this region, are a visual manifestation of the extreme state of the atmosphere. These clouds give a very strong signal and can be seen even by eye from ground, although the vertical optical thickness is only about 10-5. Nevertheless from 1018 photons (~100 MW peak power) emitted by the laser only a few are recorded by the detectors. As lidars deliver information only in a small sounding volume the combination with observations from the polar mesosphere cloud imager (CIPS) on the AIM satellite allows to study the dynamics in the mesopause region on larger horizontal scales. Applying state of the art groud based imaging allows to study dynamical processes in NLC extending satellite and lidar observations to extremely small horizontal and temporal scales (<100m, 1sec). Instrumental aspects of lidars, observations and scientific results will be presented.