The effects of precipitation on the moist potential vorticity substance (MPVS) are investigated by analyzing the MPVS with precipitation mass forcing and its impermeability in daily 1° × 1° data of the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) over the Yangtze River Basin from 21 June to 2 July 1999. The results show that the positive MPVS anomalies appear mainly along the Meiyu front, where the maximum MPVS collocates with the maximum surface rainfall. Rain case diagnoses indicate that the MPVS anomaly may be used as a dynamical signal to detect the location and shift of the rain band when its impermeability is considered.
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