Greetings,
Tropopause is usefull for the FMS for atmosphere modeling throught which your flight is taking place.
The FMS will use delta ISA up to the tropopause then delta ISA equal to Zero above the tropopause.
Also note that Winds increase by 4% per 1000 ft below the tropopause and decrease by 5% per 1000 ft above the tropopause.
