Global Hourly-Updating Data Assimilation

Laura Slivinski

Tuesday, Apr 13, 2021, 2:15 pm
Webinar

Abstract

Currently, the US global forecast system uses a 6-hour data assimilation window, providing analyses from which to initialize forecasts every 6 hours. This is too long of a window to provide accurate information on rapidly-evolving systems such as hurricanes and continental convective storms. In order to improve forecasts of these storms, shorter assimilation windows will be necessary. To this end, we are testing different approaches for updating the global forecast system every hour. One challenge for hourly updating is data latency: many observations are not available for assimilation until 1-2 hours after the valid observation time. A possible solution is to implement overlapping assimilation windows, in which the system is updated every hour with observations that have arrived within the last hour, but that are valid in a longer window (3-6 hours), removing the need for a separate 6-hourly global system. This technique will be described, including the implementation and effects of the 4D incremental analysis update in an hourly context. Preliminary results with GFSv15 will be shown.