1,721,007 research outputs found
A 1-D model of the formation and evolution of Polar Stratospheric Clouds
No full textA 1-D model of the formation and seasonal evolution of Polar Stratospheric Clouds (PSCs) is described. The model considers PSCs of types 1 and 2 in the vertical range from 8 to 30 km and utilizes real temperature data. The micro-physical processes included in the model are the heterogeneous nucleation and condensation (or evaporation), while sedimentation, gas diffusion and vertical wind velocity are the processes responsible for transport. Model simulations have been compared with PSC data obtained by lidar at the South Pole: results for the winter 1990 are discussed. The different contribution of type 1 and type 2 PSCs to the measured backscattering coefficient has been evidenced. In the simulations, layers of NAT particles form when low values of the backscattering coefficient are measured; similarly, ice particles form when sharper and rapidly changeable structures with higher values of the backscattering coefficient are observed. Significant results on the condensation and depletion of HNO3 and H2O are presented. Water vapor profiles measured during winter 1990 are reproduced quite well
IS OZONE DESTROYED DURING THE ANTARCTIC WINTER IN THE PRESENCE OF POLAR STRATOSPHERIC CLOUDS
No full textLidar observations of the Pinatubo aerosol at Thule, Greenland: relationships with the polar vortex.
No full textConvective characteristics of nocturnal urban boundary layer observed with Doppler sodar and Raman lidar
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Effects of atmospheric scattering and extinction on the retrieval of fluorescence and Cerenkov signals produced by extreme energy cosmic rays and neutrinos from space: role of lidar for their assessment and correction
No full textThe impact of extreme energy cosmic rays on the Earth’s atmosphere is manifested by the generation of fluorescence
and Cherenkov radiation: these effects constitute source fields that propagate and, once detected, provide an indirect
way to deduce energy, trajectory, composition of the primary particle. Because of the relatively infrequent probability
of detection of such effects at the ground, proposals have been advanced to observe them from space: one of the
proposed experiments is EUSO (Extreme Universe Space Observatory). Both the generation and propagation of these
fields are affected by the high variability of the atmospheric conditions: to limit the deriving uncertainties, the observations
would greatly benefit by the support of adequate instrumentation to provide the status of the atmosphere at the
time of detection. Thus the use of an optical radar––lidar––has been suggested to complement the EUSO capability.
This paper discusses: (a) the distortion induced by different atmospheric conditions on the fluorescence and Cherenkov
profiles acquired from space; (b) the lidar retrieval of the transmission and scattering characteristics of the atmosphere
and the use of these data to correct the detected signals to reach a realistic assessment of the atmospheric sources and of
the primary particle characteristics. The simulations are based on experimental results with regard to aerosol and cloud
backscatter data, on a relatively simple transfer model and on realistic assumptions regarding the extinction to
backscatter ratio
Estimation of atmospheric water vapor flux profiles in the nocturnal unstable urban boundary layer with Doppler sodar and Raman lidar
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