Impact of FY-3A MWTS radiances on prediction in GRAPES with comparison of two quality control schemes

The impact of Microwave Temperature Sounder (MWTS) radiances on the prediction of the Chinese Numerical Weather prediction (NWP) system-GRAPES (Global and Regional Assimilation and PrEdiction System) with comparison of two Quality Control (QC) schemes was researched. The main differences between the two schemes are cloud detection, O-B (brightness temperature difference between observation and model simulation) check and thinning. To evaluate the impact of the two QC schemes on GRAPES, a typhoon case study and cycle experiments were conducted. In the typhoon case study, two experiments were conducted using both the new and old QC schemes. The results show that outliers are removed in the new QC while they exist in the old QC. The analysis and the model forecast are subsequently generated after assimilating data from the two QC schemes. The model-predicted steering flows more southward with the new QC scheme, and as a result, the forecast track in the experiments is more southward, i.e., closer to the best track than the old scheme. In addition to the case study, four impact cycle experiments were conducted for 25-day periods. The results show that the new QC scheme removed nearly all the biases whereas the old scheme could not. Furthermore, the mean and standard deviation of analysis increments with the new scheme is much smaller than those of O-B. In contrast, the old scheme values are either slightly smaller or the same. Verifications indicate that forecast skill is improved after applying the new scheme. The largest improvements are found in the Southern Hemisphere. According to the results above, MWTS with the new QC scheme can improve the GRAPES forecast.