The effect of asymmetric flow on the 3-dimensional symmetric bogus vortex called as Structure Adjustable Balanced Vortex (SABV) was investigated for 9 tropical cy-clones (TCs) which affected the Korean peninsula observed in Northwest Pacific (NWP) from 2010 to 2012. The basic concept of the new asymmetric extraction process was based on the Fleet Numerical Oceanography Center (FNOC), Japan Meteorological Agency (JMA), and Geophysical Fluid Dynamics Laboratory (GFDL).
To separate the atmospheric flows, the high-order spectral filter (HSF) for the elabo-rate filtering was used. From the separated disturbance field, the TC asymmetric flow can be extracted by applying Fourier transform in the polar coordinate. The combined asymmetric flow with wavenumber 1 and 2 is relocated to observed TC center of Re-gional Specialized Meteorological Center (RSMC) by using Cubic spline interpolation method. If the difference of maximum wind (MWS) and sea level pressure (SLP) are over 5 ms-1 or 5 hPa, the short time integration to get the proper asymmetric flow in terms of TC intensity and pressure would be started. In the limited domain, the asym-metric flow can be obtained by applying the local filter, for example double Fourier series (DFS) Mercator map version or Fourier Finite Element Method (FFEM), to inte-grated data. When the difference is small, however, the additional time integration wouldn’t be started. In case of short time integration, the asymmetric flow is added to symmetric bogus vortex considered with 15 ms-1 radius.
To investigate the effect of asymmetric flow for 65 cases, the WRFV3.4.1 model was set to have a single domain with 12 km resolution. The model parameterizations werqe activated to Yonsei University PBL, WRF Single-Moment 6-Class Microphysics, and Kain-Fritsch Convective parameterization scheme, etc. With asymmetric flow on SABV, the track errors were decreased about 18.9% and 17.4% at 48 h and 72 h for symmetric SABV. The intensity and pressure errors tend to be reduced in early time. These results are meaning that the asymmetric flow should be added to symmetric SABV initialization process for better performance of SABV.