Impact of incremental analysis update initialization under the replay configuration on forecasts of a squall line event in southern China

A squall line system that occurred on 9-10 April 2016 over southern China was used to investigate the impact of incremental analysis update (IAU) initialization under the replay configuration on its forecasts. The ERA5 global reanalysis and the forecast field of the regional Weather Research and Forecasting (WRF) Model were used to construct the analysis increment. The results showed that IAU initialization reduced the imbalance caused by the introduction of the low-resolution global reanalysis into the high-resolution regional WRF model and retained the microphysical information in the forecast field of the regional WRF model, which reduced the spin-up time. Compared with the cold start run initialized directly by the ERA5 reanalysis, the linear structure and precipitation distribution of the squall line system using IAU initialization were closer to those in the observations. Further analyses indicated that the improvement of the squall line forecasts using IAU initialization was mainly related to the faster development of cold pool caused by retaining the microphysical information in the forecast field of the regional WRF model and the more favorable stratification conditions corrected by the IAU increment.