Analysis of water vapor LIDAR measurements during the MAP campaign: evidence of sub-structures of stratospheric intrusions P. D'Aulerio1,2, F. Fierli1, F. Congeduti1, and G. Redaelli2 1Institute for Atmospheric Sciences and Climate, CNR, Roma, Italy 2Department of Physics, University of L’Aquila, L’Aquila, Italy
Abstract. This paper presents two case studies of transport of dry air in the free
troposphere measured by a ground based Raman LIDAR in the Northern-Italy,
during the Mesoscale Alpine Programme (MAP). Two observations characterized
by the presence of anomalously dry layers, below 6 km height, were analyzed
using Lagrangian techniques. These events are related to upper-tropospheric,
high Potential Vorticity (PV) streamers crossing the Alpine region. These
are interpreted as small-scale features of stratospheric intrusions
associated with the PV ridge during its phase of dissipation. One of the
measurements also shows the presence of two distinct dehydrated structures
associated with the same event. The water vapor concentration also suggests
dilution processes of dry stratospheric air in the troposphere. Lagrangian
simulations allowed to successfully reproduce the observed water vapor
distribution and the air parcel histories confirmed the stratospheric origin
of the dry layers.
Citation: D'Aulerio, P., Fierli, F., Congeduti, F., and Redaelli, G.: Analysis of water vapor LIDAR measurements during the MAP campaign: evidence of sub-structures of stratospheric intrusions, Atmos. Chem. Phys., 5, 1301-1310, doi:10.5194/acp-5-1301-2005, 2005.