17.3
Secondary potential vorticity banners over the Po valley: observation and numerical simulation of their influence on vertical mixing
PAPER WITHDRAWN
Cyrille N. Flamant, Service d'Aéronomie, IPSL/CNRS, Paris, France; and E. Richard, M. Sprenger, C. Schär, L. B. Nance, and R. Rotunno
This paper seeks to provide experimental insight into the structure of the secondary potential vorticity banners (PVB2) forecasted by the Swiss-Canadian model MC2 over the Po Valley on 8 November 1999, using aircraft data and airborne lidar measurements acquired during the Mesoscale Alpine Programme (MAP) Special Observing Period (SOP) (which took place between 7 September and 15 November 1999). The PVB2 mission performed on 8 November 1999 (IOP 15) was unique in the sense that it envolved 3 aircraft flying at 3 levels (950, 850 and 720~hPa) along a box-shaped flight track with two east-west oriented legs approximately 350~km long running parallel to the Alps (approximately perpendicular to the flow). This enabled to compute the PV experimentally at the intermediate level. Since there have been few non-idealized studies of PVB2 using high-resolution numerical models, the 8 November 1999 event was simulated down to 2-km horizontal resolution using the mesoscale non-hydrostatic model Meso-NH in order to gain insight into the three-dimensional structure of this features. This paper addresses several questions, including the following:
- How accurately can a high resolution operational model forecast secondary PV banners?
- Can PV be calculated using aircraft in situ measurements?
- What is the structure of the PV banners observed experimentally? How does the structure of the secondary PV banners evolve away from the Alps? How does it compare with simulation outputs?
- How well can a high resolution mesoscale model simulate secondary PV banners?
- What is the influence of secondary PV banners on lower-tropospheric thermodynamics and on the vertical structure of the atmospheric boundary layer (ABL) over the Po Valley?
Session 17, Lee-Side Phenomena
Friday, 21 June 2002, 8:00 AM-9:00 AM
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