Evidence of changes in diffusive properties over Italy during the period November 2006-April 2007: A case study.

Extended winter 2006-2007 and April 2007 have been characterised by strong positive anomalies in temperature and pressure fields over Italy and part of the European continent. In this framework, first evidence of the influence of this situation on boundary layer diffusive properties is shown here. This is achieved by estimations of Pasquill's classes from surface observations at Rome-Fiumicino meteorological station and an analysis of their frequencies of occurrence vs. a 33-year local diffusive climatology.