Views
3 years ago

Bred vectors and forecast errors in the NASA coupled general ...

Bred vectors and forecast errors in the NASA coupled general ...

(Weaver et al., 2003,

(Weaver et al., 2003, Vialard et al. 2003), have shown their advantages in the tropical Pacific and have a positive impact on the ENSO forecasts. However, even in these advanced methods, it is difficult to include the impact from coupled processes needed for better initialization for ENSO prediction when constructing the background error covariance (e.g., uncertainties in the wind forcing). Moreover, the computational cost of these advanced techniques is still a major concern. Therefore, we propose to test the use of bred vectors obtained from the CGCM to provide information related to coupled error structures at a very low computational cost. If indeed there are similarities between bred vectors and forecast errors (which we will determine according to our first goal), BVs have the potential to provide information related to the slowly varying, coupled error structure in the OI scheme by augmenting the time-independent background structure with flow dependent structure (Corazza et al. 2002 and Yang et al, 2006). Alternatively, the BVs can be used in conjunction with the background error structure derived from the ocean EnKF of Keppenne et al (2002) for better description of background uncertainties and to alleviate the need for a large ensemble. Therefore, in this study we would like to examine how well the structure of the forecasterrors of the month” is represented in the CGCM with bred vectors. We will examine the characteristics of the one-month forecast error and bred vectors against the evolving background state. If an apparent link can be diagnosed among these quantities, the structures captured by bred vectors can be applied as the ensemble perturbations not only for projecting on the dominant seasonal-tointerannual associated variability but also for an augmentation of the error covariance structure in oceanic data assimilation scheme. 8

Our paper is organized as follows. In section 2, we briefly introduce the NASA coupled general circulation model (GCM) used for experimental forecasts and the setup of the coupled breeding experiments. Section 3 describes the relationship between bred vectors and forecast errors. The application of bred vectors in ocean data assimilation scheme is discussed in section 4. The summary and discussion are given in section 5. 2. Description of the breeding experiments in the GMAO operational system 2.1. The NASA GMAO coupled GCM The GMAO coupled model is a fully coupled global ocean-atmosphere-land system developed at NASA Goddard Space Flight Center (GSFC) (Vintzileos et al. 2003). It is comprised of the NSIPP-1 atmospheric general circulation model (AGCM, Suarez 1996, Bacmeister and Suarez 2002; Bacmeister et al. 2000), the Poseidon ocean model (OGCM, Schopf and Loughe 1995, Yang et al. 1999), and the Mosaic land surface model (LSM, Koster and Suarez 1992) all developed for the purpose of improving seasonal to interannual prediction. The model variables of the ocean GCM are arranged on isopycnal layers; they are thickness, temperature, zonal and meridional current velocity and salinity. The oceanic grid resolution is 5/8˚ in longitude, 1/3° in latitude and 27 layers in vertical. The model variables of the atmospheric components are prescribed in sigma coordinates; they are surface pressure, zonal and meridional wind, potential temperature and specific humidity. 9

Forecast-error-sensitivity to observations in the UM - NASA Global ...
Relationship between singular vectors, bred vectors, 4DVar, and EnKF
Decadal North Pacific Bred Vectors in a Coupled GCM - Paul Schopf
Relationship between Singular Vectors, Bred Vectors, 4D-Var and ...
Ensemble Dynamics and Bred Vectors - SAMSI
Ensemble Forecasting at NCEP - Weather-Chaos Group
Generalized Forecast Errors, A Change of Measure, and Forecast ...
Sensitivity of Forecast Errors to Initial Conditions ... - Inscc.utah.edu
Error Measures For Generalizing About Forecasting Methods ...
Characterization of mixing errors in a coupled physical ... - HAL
Predicted errors of tropospheric emission spectrometer ... - TES - Nasa
Sources of Skill and Error in Long-Range Streamflow Forecasts for ...
Flood forecast errors and ensemble spread—A ... - idrologia@polito
An Examination of Model Track Forecast Errors for Hurricane Ike ...
Mesoscale Ensemble Forecast Experiment and Sensitivity Analysis ...
General Characteristics of Stratospheric Singular Vectors Ronald M ...
Relationship of Seasonal Climate Forecast Error to ... - GOAPP
Initial state perturbations in ensemble forecasting - Nonlinear ...
Measuring forecast errors in a Met Office high- resolution model