3 VALIDATION OF BOUNDARY-LAYER PARAMETERIZATIONS IN A MARITIME STORM USING AIRCRAFT DATA

Processes both near the surface and aloft in interstorm regions of maritime extratropical cyclones can produce significant effects on the development of the systems along the storm track. Large surface fluxes in cold air outbreaks behind a passing system can play a significant role in preconditioning the atmosphere for the development of the next frontal wave, as suggested by Reed and Albright (1986). They suggest the possibility that the surface fluxes alter the low-level baroclinicity of the prestorm environment for the subsequent storm, thereby affecting its development on a 24-hour time scale. Surface heat fluxes can impact the low and mid-level stability of a storm on slightly shorter time scales, as seen for a comma cloud producing strong convection in California during the 1982/83 El Nino season (Reed and Blier 1986). Observations obtained with the NOAA P-3 aircraft on February 6-7, 1998, during the California Landfalling Jets Experiment (CALJET; Ralph et al 1999) are used to document the processes occurring in the interstorm environment and to validate several planetary boundary layer (PBL) parameterization schemes using two methods. Off-line validation uses the observed mean flow and thermal characteristics, while 3-D modeling with the Penn State/NCAR Mesoscale Model (MM5) relies on the model atmosphere and surface characteristics. The Blackadar (Blackadar 1976; Zhang and Anthes 1982), the operational Medium Range Forecast Model (MRF) (Hong and Pan, 1996), and the Burk-Thompson (Burk and Thompson, 1989) PBL schemes are used. The first two use non-local schemes with first-order closure, while the last uses a local scheme with second-order closure. Only the 3D modeling will be presented in this paper, but the off-line results will be shown at the conference.