APPLICATION OF A NEW LAND-SURFACE, DRY DEPOSITION, AND PBL MODEL IN THE MODELS-3 COMMUNITY MULTI-SCALE AIR QUALITY (CMAQ) MODEL SYSTEM

摘要

Preliminary analysis of the sensitivity of the CMAQ system to inclusion of a more sophisticated land surface model with consistent treatment of dry deposition shows substantial effects on one of the most important model outputs, namely ozone concentration. The PX runs generally produce lower ozone concentrations than the base runs. This difference is probably mainly due to the tendeacy of the MM5-PX to produce greater amounts of cloudiness, which reduces photolysis rates and the greater ozone dry deposition velocities from the M3Dry deposition model. It is interesting that the greater cloudiness simulated by the MM5-PX does not similarly reduce temperature and height compared to the Base MM5. Therefore, the PX LSM not only changes many of the surface, PBL, and cloud parameters but also alters the relationships between them. The Plymouth, NH case study does not show such systematic differences in ozone concentration between the PX and Base runs as seen in the averaged results, particularly during the clear period on days 2 and 3. This case does show considerable differences caused by the different meteorological simulations such as the huge difference in concentration during the early morning of the third day and the difference in the late afternoon peak. The different dry deposition models may play a significant role in the nighttime differences but probably not during the daytime when the dry deposition velocities from the two models were very similar (see Figure 4D). It will take further analysis to differentiate the effects of the model changes in meteorology and dry deposition. This preliminary study demonstrates the value of a flexible, comprehensive, air quality modeling system for developing and evaluating new modeling techniques. Evaluations of modeling advancements need to be performed at both the component level and the integrated level to assess relevance to the ultimate products. In this way the greatest attention can be paid to the weakest links in the system.