The Upgrade of GRAPES_TYM in 2015 and Its Performance and Problems

The regional typhoon model GRAPES_TYM was upgraded in June 2015. The changes include the two aspects:（1）Increasing model vertical and horizontal resolution from 15km/L31 to 12km/L50; (2) Fix one bug in the surface layer program in the calculation of roughness length. The increasing of model resolution could improve the track and intensity forecast especially could reduce the large north-ward bias of GRAPES_TYM ; The fix of the bug in surface layer could reduce the fast spin-up of Tc vortex during 0-12h and strong positive bias for TCs with slower deepening rate. The rerun results for 2013-2014 show that the upgrade of GRAPES_TYM could reduce the track (intensity) errors by 8% (17%)/24h, 17% (20%)/48h, 20% (18%)/72h,28% (21%)/96h and 33% (23%）/120h. The operational results in 2015 indicate that GRAPES-TYM still has obvious northward bias for TC tracks especially for the TCs during their TD and TS stage; For TC intensity, the upgraded GRAPES_TYM couldn't produce Super Typhoon（maximum wind speed greater than 51.0m/s.