Typhoon-position-oriented sensitivity analysis
Journal
Part I: Theory and verification. J. Atmos. Sci.
Journal Volume
70
Pages
2525-2546
Date Issued
2013
Author(s)
Ito, K.
Abstract
A new sensitivity analysis method is proposed for the ensemble prediction system in which a tropical cyclone (TC) position is taken as a metric. Sensitivity is defined as a slope of linear regression (or its approximation) between state variable and a scalar representing the TC position based on ensemble simulation. The experiment results illustrate important regions for ensemble TC track forecast. The typhoon-positionoriented sensitivity analysis (TyPOS) is applied to Typhoon Shanshan (2006) for the verification time of up to 48 h. The sensitivity field of the TC central latitude with respect to the vorticity field obtained from large-scale random initial perturbation is characterized by a horizontally tilted pattern centered at the initial TC position. These sensitivity signals are generally maximized in the middle troposphere and are far more significant than those with respect to the divergence field. The results are consistent with the sensitivity signals obtained from existing methods. The verification experiments indicate that the signals from TyPOS quantitatively reflect an ensemble-mean position change as a response to the initial perturbation. Another experiment with Typhoon Dolphin (2008) demonstrates the long-term analysis of forecast sensitivity up to 96 h. Several additional tests have also been carried out to investigate the dependency among ensemble members, the impacts of using different horizontal grid spacing, and the effectiveness of ensemble-Kalman-filter-based perturbations. © 2013 American Meteorological Society.
SDGs
Other Subjects
Forecasting; Hurricanes; Vorticity; Ensemble Kalman Filter; Ensemble prediction systems; Ensemble simulation; Forecast sensitivity; Horizontal grid spacing; Initial perturbation; Long term analysis; Position-oriented; Sensitivity analysis; climate prediction; ensemble forecasting; numerical model; sensitivity analysis; typhoon
Type
journal article