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 regionЕЧs 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 ЕШpole-to-poleЕЩ 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.