Resolution Dependence of Singular Vectors Computed for Typhoon SINLAKU

Abstract

To investigate the resolution dependence of singular vector (SV) for Typhoon SINLAKU in the recurvature stage, SVs were computed using the Japan Meteorological Agency (JMA) tangent linear and adjoint (hereafter TL/AD) model at three different resolutions of TL63L60¹, TL95L60 and TL159L60.
The results show that depending on the horizontal resolution, SVs have their own peak energy height and spectral shifts from the initial to final time due to the difference of detectable influences from mid-latitude troughs and tropical cyclone (TC) surrounding flows. On the other hand, common features of wind fields are found among the three SV structures. As for the SV using the TL/AD model at a TL159L60 resolution, the 48 hour optimization time interval (OTI) provides a larger influence from mid-latitude troughs with higher peak energy height than in the case with 24 hour OTI.
Those results suggest that in the present case of a recurving TC using dry SV with a dry total energy (TE) norm, a certain degree of resolution in the TL/AD model is required to effectively detect sensitive areas around the TC because the resolution can change the energy balance among the mechanisms contributing to the SV structure.

¹ We use T as an abbreviation for triangular truncation with Gaussian grid, TL for triangular truncation with linear Gaussian grid and L for vertical layers. Therefore, TL63L60 denotes spectral triangular truncation at 63 wave numbers with linear Gaussian grid and 60 vertical layers.