The high frequent occurrence of low ceiling stratus or fog in summer season in the San Francisco Bay area makes San Francisco International Airport (SFO) the first in the number of imposed delay program in the nation, during which the airport has to stop using independent parallel approaches, decreasing the arrival capacity by one half. Other major coastal airports also have the problem of marine stratus. Analysis shows that most of the unnecessary delay and a large amount of holding could be eliminated if accurate one-hour predictions of the onset and burnoff times of the marine stratus could be provided. In this study, the ARPS model (Advanced Regional Prediction System) developed by CAPS (Center for Analysis and Prediction of Storm) at the University of Oklahoma, a 3D limited-area, nonhydrostatic and fully compressible mesoscale model with generalized terrain-following coordinate plus a wide scope of options in turbulence treatment, surface layer and radiation parameterization, cloud microphysics, and data analysis and assimilation techniques, has been used in an attempt to simulate the marine fog and low ceiling stratus in San Francisco Bay area, with the focus on the burnoff process around the San Francisco International Airport (SFO).
The NCEP ETA (40km) output is currently used on the days with marine fog- stratus event off California coast and/or over the target region (SFO) to generate initial and boundary conditions. Three levels of grids are used: 18km, 6km, and 2km, in which the coarser domains provide initial and boundary conditions for the finer domains. The innermost domain, with high resolution (1km) terrain data), is the one for the forecast of the burnoff around SFO. The comprehensive ADAS (ARPS Data Analysis System) is applied with the ingestion of various observation dataset, including the surface and sounding data from SFO Marine Stratus Initiative (MIT/LL), possible Mesonet data, the NRL-Monterey GOES-9 fog-low stratus products, and the NSCAT (NASA Scatterometer) ocean surface wind data, to generate better initialization of the coastal marine boundary. The simulation experiments show that the model is able to produce correct pattern of fog-stratus system even without any specific data analysis, with the ability to capture the burnoff process over the coastal land after sunrise. With the help of various data analysis, esp. the cloud and wind analysis, the simulated cloud pattern and the onset time are greatly improved. The high resolu- tion (2km) simulation shows potential to capture the burnoff time and location around the airport, provided accurate low level wind field.
The 8th Conference on Aviation, Range, and Aerospace Meteorology