Human induced changes in the global climate and atmospheric
environment are among the most significant scientific challenges of
this century. The growing interest in the middle and upper atmosphere
(about 30-120 km) is tied to this region¡Çs importance for detecting
and understanding the global climate change. While the greenhouse
gases such as CO2 and CH4 help warm the lower atmosphere by absorbing
infrared radiation, they are also efficient radiators of heat and
result in the cooling in the middle and upper atmosphere. Models of
the global atmosphere are used to understand these issues and to
project the future state of the climate and the environment. However,
large uncertainties remain in these models, owing to the lack of high
quality measurements of key parameters, especially in the middle and
upper atmosphere region. Improved treatment of gravity waves and
aerosols in models will come about only through improved
observations. Similarly, global climatology of temperature and winds
are needed to provide the crucial tests of models as well as the means
to monitor global climate change. Among the technologies employed to
study this region, LIDAR techniques are unique in their abilities to
provide high-resolution data on key parameters, such as temperature,
winds, clouds and aerosols, and gravity waves, with full diurnal and
annual coverage.
I have been deeply involved in the design, development and deployment
of several different resonance fluorescence / Rayleigh lidars and made
numerous observational studies of the middle and upper atmosphere from
the North Pole to the South Pole. I will briefly introduce the
research campaigns that we made with a broadband Fe (iron) Boltzmann
temperature lidar in the Arctic and Antarctica. Then I will
concentrate on the scientific results obtained from these
¡Èpole-to-pole¡É lidar observations to emphasize the scientific
findings on the inter-hemispheric difference in polar mesospheric
clouds (PMC), heterogeneous removal of Fe atoms on PMC ice particles,
and the shuttle-introduced PMC and Fe layers. Our understandings to
these phenomena will be provided. The constraints on atmospheric
general circulation and chemistry models provided by the observed
temperatures and seasonal variations of Na and Fe densities will also
be discussed. These results show examples how the lidar observations
can contribute to the tests of large-scale dynamics in atmospheric
models. Following this, the newly proposed next generation lidar (the
most advanced mobile Fe-Resonance/Rayleigh/Mie Doppler lidar) will be
discussed as part of the future outlook, along with the exciting
science we can pursue with future lidars.
Photos and movies taken from Antarctica may be shown at the end of this talk.