According to the TIGGE+ list specific humidity (qv) is missing and can be calculated using Temperature, Pressure and relative Humidity according to:
zpvs = b1*EXP( b2w*(t(i,j,k)-b3) / (t(i,j,k)-b4w) )
zp = p0(i,j,k) + pp(i,j,k)
zqvs = rdv*zpvs / (zp - o_m_rdv*zpvs)
! Set minimum value of relhum to 0.01 (was 0 before)
relhum(i,j,k) = MAX( 0.01_ireals, qv(i,j,k)/zqvs * 100_ireals )
zp pressure in Pa, t temperatur in K, qv specific humidity in kg/kg and
rdv = r_d/r_v
o_m_rdv = 1 - r_d/r_v
with
r_d = 287.05_ireals
r_v = 461.51_ireals
b1 = 610.78_ireals
b2w = 17.2693882_ireals
b3 = 273.16_ireals
b4w = 35.86_ireals