Accession Number:

ADA571385

Title:

Estimation and Calibration of Observation Impact Signals Using the Lanczos Method in NOAA/NCEP Data Assimilation System

Descriptive Note:

Journal article

Corporate Author:

NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS OCEANOGRAPHY DIV

Report Date:

2012-09-25

Pagination or Media Count:

18.0

Abstract:

We use the Lanczos method in the NCEP the National Centers for Environmental Prediction Gridpoint Statistical Interpolation GSI DA system to look into the important aspects and properties of this method. We apply this method to estimate the observation impact signals OIS which are directly related to the analysis error variances. It is found that the smallest eigenvalue of the transformed Hessian matrix converges to one as the number of minimization iterations increases. When more observations are assimilated, the convergence becomes slower and more eigenvectors are needed to retrieve the observation impacts. It is also found that the OIS over data-rich regions can be represented by the eigenvectors with dominant eigenvalues. We have proposed four different calibration schemes to compensate for the missing trailing eigenvectors. Results show that the method with proper calibrations for a small number of eigenvectors enhances and improves the impact signals over regions with more data

Subject Categories:

  • Meteorology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE