Assimilation of cloud-top pressure derived from GOES sounder data into MAPS/RUC

FSL has developed and begun real-time testing of an initial assimilation technique using the cloud-top product from NESDIS (based on GOES sounder). This product, available hourly, is being assimilated into a test version of MAPS (which also runs as the Rapid Update Cycle at NCEP).

MAPS/RUC provides explicit forecasts of mixing ratio for 4 hydrometeor types -- cloud water, rain water, ice, and snow. Thus, background vertical profiles of these hydrometeors, as well as water vapor, are available each hour from the previous 1-h forecast as part of the 1-h MAPS/RUC assimilation cycle.

These hydrometeor and water vapor profiles are adjusted at each grid point where GOES cloud-top pressure data are available. Clouds may be built or cleared or vertically clipped depending on the difference between the background hydrometeor profile and the GOES cloud-top pressure.

This initial GOES-based cloud analysis was put into parallel run, and cloud forecasts were verified for 1,3,6,9, and 12 hour predictions compared to a control run without assimilation of GOES cloud-top pressure. Initial results show a strong positive impact in 1-h cloud forecasts, and even a smaller but consistent impact in 12-h cloud forecasts.