Since the output variables that are generated by an MM5 simulation are not always useful in their “raw” form, those variables must be converted into fields that are required by the chemistry and emission models. The conversion of MM5 output to useful fields for CMAQ is accomplished in the Meteorology Chemistry Interface Processor (MCIP), which is discussed in Section 2.3.1. MCIP computes variables that are useful to the subsequent models in CMAQ, and it creates an output file written with the I/O API libraries in netCDF format, which is standard in the CMAQ modeling system.