Key Technologies of CMA-MESO and Application to Operational Forecast

To meet the requirement of numerical weather prediction for local severe convective weather,especially disastrous weather and extreme weather events,based on GRAPES-MESO 10 km system,many works have been completed,which include improving the calculation accuracy and stability of the model dynamic framework,selecting and testing the physical parameterization schemes suitable for high-resolution model,establishing a national radar quality control preprocess system,applying the national（SA/SB/CB） threedimensional network mosaic data through the cloud analysis system,establishing a convective resolvable assimilation system and land surface data assimilation system for small and medium-scale systems,implementing the assimilation and application of unconventional local dense data such as radar radial wind,wind profile radar,FY-4 A imager emissivity,satellite cloud motion wind,satellite GNSSRO,surface precipitation and the near surface data,and developing the rapid cycle technology.By integrating all the jobs mentioned above,the nationwide rapid analysis and forecast system CMA-MESO（GRAPES-MESO 3 km）has been established and put into operational run since June 2020 with 3 km horizontal resolution and 3 h time interval.The operational verification results in flood season from June to September of 2020 show that the forecasts of near surface elements（precipitation,2 m temperature and 10 m wind） of CMA-MESO forecast surpass the results of GRAPES-MESO 10 km system,and the threat score for 3 h accumulated precipitation forecast is outstanding.The threat score for 24 h accumulated precipitation of CMA-MESO is slightly worse than the result of ECMWF,but the threat score for 3 h accumulated precipitation forecast is significantly better.For the precipitation exceeding 10.0 mm,CMA-MESO performs better than ECMWF within all the lead times,and the advantages are more obvious with the increase of precipitation threshold.Compared to ECMWF,CMA-MESO shows more obvious advantages on daytime forecast.For 25 mm precipitation threshold,the improvement rate exceeds 50% in most of the daytime and reaches about 100% in the later stage of forecast.The spatial distribution of mean 24 h accumulated precipitation predicted by CMA-MESO and ECMWF models is close to the observation,but the amount predicted by CMA-MESO is slightly larger.The frequency and intensity of precipitation simulated by CMA-MESO,which can characterize the ability of model to predict the spatial-temporal fine characteri