2007 Workshop:Tutorial Summary
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Summary of the 2007 CEDAR Tutorials
Diego Janches
This year the workshop tutorials were selected to provide more in-depth review of the background and state-of-the-art research and knowledge of the topic that was selected for the prize lecture given by Dr. John Plane. We were honored that Diego Janches (CORA division of NWRA) gave the lead-off tutorial on the topic of meteor observations titled "The micrometeor flux in the MLT". Beginning with a summary highlighting the significant milestones involving meteor observations within the CEDAR community (including his CEDAR postdoc award in 2001), Diego listed the reasons why meteors are of interest to CEDAR: (1) they tell us about the neutral winds and large-scale atmospheric dynamics, (2) they are the source of mass input for various atmospheric phenomena, (3) they allow us to study meteor plasma physics, and (4) they are a space hazard.
The remainder of Diego's tutorial was focused on the questions of "How much mass is coming?", "Where is it coming from?" and what is the CEDAR community doing to solve these questions. Diego showed that current models for the mass flux do not accurately predict the total mass input over the range of observations. He then showed that the two questions were actually linked and that source of the meteors had a big impact on the observations. He discussed the importance of understandingobservational biases and showed promising modeling results which give good agreement with observations when the relative contributions of the sources ofmeteors, atmospheric effects and instrument response functions are taken into account.
David Siskind
David Siskind's tutorial was entitled "State of the Art of Mesospheric Modeling". It began by discussing the various three dimensional global models of the mesosphere, emphasizing the differences between climate models and weather models. He gave a specific example of each, with the NCAR/WACCM model being representative of the former and the NRL/NOGAPS-ALPHA (Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude) being representative of the latter. He then gave a brief summary of recent WACCM work in modeling trends in middle atmospheric ozone, temperature and water vapor based upon a recent publication in JGR by Garcia et al. In brief, the simulated trends in ozone and temperature were in good agreement with historical observations, but the water vapor trend was not. This may be due to low frequency interannual atmospheric variability not yet accounted for by the WACCM model.
The rest of his talk was an in depth discussion of recent work using NOGAPS-ALPHA to hindcast unusual mesospheric meteorological conditions observed in recent NH winters. The data come from the NASA/TIMED-SABER instrument and they show a 30 km vertical displacement of the winter stratopause in early 2006 and 2004. These years also coincide with enhanced transport of nitric oxide from the thermosphere to the stratosphere. Siskind summarized several NOGAPS-ALPHA simulations with various different parameterizations of orographic and non-orographic gravity waves. He concluded that the filtering of these waves during the strong stratospheric warming of late January and early February 2006 led to the anomalous mesospheric wind and temperature patterns. Since the filtering of mesospheric gravity waves is governed by the large scale stratospheric flow and since these waves, in turn, ultimately impact the degree to which NO from the thermosphere is transported to the stratosphere, the study of mesospheric variability adds a new paradigm to solar-terrestrial studies. Rather than simply considering various solar and geomagnetic cycles, Siskind concluded that one needs to consider the meteorological state of the entire atmosphere as an important mediating factor in solar-terrestrial coupling.
John Meriwether
The third CEDAR 2007 tutorial was given by John Meriwether of Clemson University on the "State of the Art in Mesosphere Science" This talk provided a short summary of the basic fundamentals of the mesosphere and of the instrumental techniques used for mesosphere observations. This topic was chosen by the CSSC for one of the tutorial lectures following the theme of expanding the meteor research presented by John Plane in the prize lecture. The mesosphere is the entry region of meteoric debris. It is a region of 20-30 km thickness with marginal dynamical stability. The dynamics are highly influenced by gravity and tidal waves. This talk also described MLT dynamics in regard to the formation of (1) mesosphere inversion layers (MIL) and (2) instability layers with an emphasis placed upon experimental observations obtained by CEDAR instrumentation such as the lidar and all sky imaging system. The viewgraphs for this lecture, along with additional material on this subject, have been provided by John Meriwether.
