Comparison of online and offline modeling with WRF/chemT

Julius Chang
National Central University, Taiwan


At National Central University our group has continued with the development of WRF/chemT with online emissions and other improvement to WRF/chem. We have now completed the basic gas-phase chemistry model components and are continuing with aerosol chemistry parts. WRF/chemT uses a Hertel type numerical solver of the gas-phase chemistry and Madronich photolysis with online cloud correction. This chemical solver is about a factor of four faster then the corresponding solver in WRF/chem. 2.2 and earlier version. Online emissions processing at each transport time step will increase emissions calculation time by a factor of 12, an acceptable increase when compared with the total modeling time. With this higher time resolution in online emissions one hopes to catch potential impact of fast changing local meteorological variations. But whether WRF meteorology can capture these ”local small scale variations” will depend on model horizontal grid resolution and the details of vertical mixing processes. In this presentation we will first introduce WRF/chemT and how it differs from WRF/chem and then discuss our preliminary findings in comparing online and offline emissions modeling.