All-sky assimilation of ATMS observations with correlated error
Research with correlated satellite observation error has been ongoing at NCEP and has primarily focused on estimating and accounting for inter-channel error correlations in AIRS and IASI observations that are free from cloud contamination. In the Gridpoint Statistical Interpolation (GSI), it is assumed that the observation errors of different satellite channels are uncorrelated. To compensate for the neglected correlations, the errors are inflated. Modifying the representation of these errors in the GSI to account for inter-channel correlations has proven to give a better weighting to these observations in the assimilation and yield a positive forecast impact in the troposphere.
In late 2018, NCEP will begin assimilating ATMS radiances under all-sky conditions, with the transition to the Finite Volume Cubed-Sphere (FV3) dynamical core. This presentation will discuss the all-sky assimilation of ATMS observations with correlated error. The estimation of the error correlation matrix will be detailed, and two approaches will be tested to account for the correlations in the all-sky configuration. First, error correlations will only be used when observations are free from cloud contamination. In the second approach, an error covariance matrix will be modeled as a function of cloud amount
Dr. Kristen Bathmann I.M. Systems Group at NCEP/EMC