Title:Rapid update cycling with overlapping windows

Author: Tim Payne (Met Office, UK)

In this talk we consider `rapid update' cycling for global NWP models, in which the analysis state is frequently (perhaps hourly) updated. Advantages include timely boundary conditions for high resolution limited area models, improved performance of data assimilation schemes due to smaller analysis increments, and potentially better affordability of DA methods as the computational load is distributed more evenly in time.

One complicating factor is that if we wish to assimilate all observations, including ones which only become available after a delay exceeding the interval between updates, the asimilation windows will need to overlap. We obtain the optimal (Bayesian) solution to this problem, and show that in the presence of model error it presents some novel features. We also consider approximate strategies which are more closely aligned with current DA methods, discuss the difficulties these approximate strategies have, and how these difficulties might be overcome.

GMAO Head: Steven Pawson Global Modeling and Assimilation Office NASA Goddard Space Flight Center

Curator: Nikki Privé Last Updated: Feb 9 2015