The principle of forecasting pollution potential index(PPI) and air pollution index(API), the method for prediction of fly ash and some parameters in CAPPS are explained and discussed for answering the questions in operational application of CAPPS.

• 针对在应用城市空气污染数值预报系统 CAPPS过程中容易出现的疑问 ,对CAPPS模式系统中污染潜势和污染指数的预报原理、模式中一些参数的意义以及扬尘的预报 ,作了进一步的说明和讨论。