Upgrades of GRAPES_TYM in 2016 and Its Performance

GRAPES_TYM was put into operational running in 2012. The error analyses of TC track for 2013-2015 show that there exist north-east ward systematic errors especially when TCs travel across the area between 130-160°E and 10-30°N. The analyses of the environmental fields including geopotential height, temperature indicate that there exist negative bias of height below about 400hPa and positive bias above 400hPa; For temperature, there exist positive bias below about 200hPa. The 500hPa geopotentialheight shows that GRAPES_TYM produces weak subtropical high.

The following improvements were integrated into GRAPES_TYM in 2016  in order to reduce the track errors: (1) Isothermal atmosphere profile was replaced by a reference profile based on the average of initial value; (2) Cumulus convection scheme was modified in order to weaken the heating rate in the ocean; (3) The long wave and short wave radiation scheme were upgraded from RRTM and Goddard to RRTMG.

The experiments results show that the above modification could reduce the negative bias of the geopotential height along the subtropical high and the systematic north-east ward bias of TC tracks.

The operational results in 2016 will also be presented in this talk.