Séminaire LATMOS (Amphithéâtre Gérard Mégie, Guyancourt), Vendredi 17 octobre 2014, 10h

Orateur: Prof. Robert J. Sica (Department of Physics and Astronomy, The University of Western Ontario)

Titre: Improved Understanding of Thermosphere-Mesosphere-Stratosphere-Troposphere Coupling Using Lidar Measurements

Résumé: 

Solar-terrestrial relations is the study of how solar radiation and particles enter and interact with Earth's atmosphere-ionosphere-magnetosphere system. The atmospheric component of solar-terrestrial relations traditionally emphasizes the interaction of solar energy with the middle and upper atmosphere. Over the last 20 years it has been realized that the coupling of the lower atmosphere with the upper atmosphere is critical to understanding climate and weather on the surface. Thus, simultaneous measurements over a wide range of heights are necessary to provide the inputs needed to understand coupling processes between atmospheric regions.    Active sensing techniques such as radar and lidar (laser radar) allow this coupling to be investigated over a wide range of heights. My group's primary research tool is the Purple Crow Lidar (PCL), which measures atmospheric composition and temperature from near the surface to the lower thermosphere (altitudes above 100 km). The PCL uses a 2.6 m diameter liquid mirror telescope coupled with a high-power laser transmitter to measure temperature, density and water vapour mixing ratio. Due to its large power-aperture product, several of its measurement capabilities are unique, such as the ability to resolve individual gravity waves and measure water vapour in the upper troposphere and lower stratosphere. In addition to the PCL, my group actively collaborates with two other lidar systems located in the high Arctic as part of the Canadian Network for the Detection of Atmospheric Change (CANDAC). Comparison of these measurements with the PCL contributes to understanding teleconnections between high and low latitudes.

The role of small scale waves on the atmospheric system will be discussed and examples will be shown of measurements we have made that demonstrate atmospheric coupling, as well as the transport of atmospheric constituents such as ozone and pollutants between the troposphere and stratosphere. Examples will also be shown of a new retrieval technique for temperature from these measurements, which will improve our ability to use these measurements to search for temperature change.

Note:Si après le séminaire vous souhaitez discuter avec le Prof. Sica, contacter Alain Hauchecorne ou Philippe Keckhut (thésards et postdoc sont encouragés à profiter de cette opportunité)