The IUSN21 TTAAii Data Designators decode as: T1 (I): Observational data (Binary coded) - BUFR T1T2 (IU): Upper air T1T2A1 (IUS): Radio soundings from mobile land stations (entire sounding) A2 (N): Northern hemisphere (Remarks from Volume-C: TeamX Campaign)
The IUXN21 TTAAii Data Designators decode as: T1 (I): Observational data (Binary coded) - BUFR T1T2 (IU): Upper air T1T2A1 (IUX): Other upper air reports A2 (N): Northern hemisphere (Remarks from Volume-C: TeamX Campaign)