| MM5 was run with three one-way nested domains (horizontal grid lengths of 36, 12, and 4 km), 32 expanding vertical-levels up to 100 hPa (first sigma level at 20 m), 1.5 higher order TKE closure, and either GDAS or ETA large-scale NCEP forcing and analyzing nudging. Analyses showed that the 700 hPa synoptic-forcing was better reproduced by GDAS, as its surface-pressure lower boundary-condition better captured central-California topographic effects than did the mean sea-level pressure boundary-condition of ETA. MM5 results for the 30 July to 02 August 2000 Central California Ozone Study (CCOS) episode showed that a strengthening coastal high at 700 hPa settled over the San Francisco Bay Area (SFBA) and then moved inland to create evolving upper-level background flows. The related movements of two surface Central Valley thermal-lows, i.e., the Fresno and Sacramento eddies, sequentially produced flows from the SFBA into Livermore, Sacramento, and San Joaquin Valley. MM5 reproduced these flows, as well as the resulting surface mesoscale sea/land and mountain/valley breezes, as well as the associated confluence zones that sequentially produced the ozone exceedances in the three areas listed above. |
