## 4 Results
### Assessment of Global Forecast Impact
To examine additional forecast benefit induced by reducing the data latency from 20 min to 5 min, we also compared the forecast errors between the latency_5m run and the latency_20m run. Figures 13 and 14 show the difference of forecast errors (i.e., AC and RMSE) of geopotential heights at three different pressure levels between the latency_5m run and the latency_20m run. For both of the ACs and RMSEs, the global mean differences are almost zero for the whole forecast hours at all three pressure levels, meaning that there are no extra forecast benefits gained by reducing the data latency from 20 min to 5 min. The forecast errors tend to increase in the Tropic and the Southern Hemisphere but decrease in the Northern Hemisphere for the latency_5m run as compared to the latency_20m run, but the error changes are not statistically significant. In addition to the geopotential height, the departures of ACs and RMSEs of temperature between the latency_5m run and the latency_20m run show a neutral forecast impact (Figures 15 and 16). The difference in the number of assimilated satellite measurements between the latency_20m run and the latency_5m run is about 5% for all IR and MW sensors (Figures 3 and 4). This slight data difference is unlikely to change the forecast impact when verified over a length of time. Figure 12: Global map of the mean difference of RMSE of (**a**,**b**) 250 hPa, (**c**,**d**) 500 hPa, and (**e**,**f**) 850 hPa temperature at (**a**,**c**,**e**) T+72 and (**b**,**d**,**f**) T+96 forecast hours between the latency_20m run and the control run. Figure 14: The (**a**) mean and (**b**) normalized difference of RMSE of 250 hPa, 500 hPa, and 700 hPa geopotential height forecast up to 120–h forecast hours between the latency_5m and latency_20m runs. Grey, green, red, and magenta boxes indicate the results over the Global, Northern Hemisphere, Tropic, and Southern Hemispheres, respectively. Vertical bars representing 95% confidence level of the uncertainty are overlaid. Figure 13: The (**a**) mean and (**b**) normalized difference of AC of 250 hPa, 500 hPa, and 700 hPa geopotential height forecast up to 120-h forecast hours between the latency_5m and latency_20m runs. Grey, green, red, and magenta boxes indicate the results over the Global, Northern Hemisphere, Tropic, and Southern Hemispheres, respectively. Vertical bars representing 95% confidence level of the uncertainty are overlaid. Figure 16: The (**a**) mean and (**b**) normalized difference of RMSE of 250 hPa, 500 hPa, and 850 hPa temperature forecast up to 120-h forecast hours between the latency_5m and latency_20m runs. Grey, green, red, and magenta boxes indicate the results over the Global, Northern Hemisphere, Tropic, and Southern Hemispheres, respectively. Vertical bars representing 95% confidence level of the uncertainty are overlaid. Figure 15: The (**a**) mean and (**b**) normalized difference of AC of 250 hPa, 500 hPa, and 850 hPa temperature forecast up to 120-h forecast hours between the latency_5m and latency_20m runs. Grey, green, red, and magenta boxes indicate the results over the Global, Northern Hemisphere, Tropic, and Southern Hemispheres, respectively. Vertical bars representing 95% confidence level of the uncertainty are overlaid.