Estimation of precipitable water and relative humidity over the Tibetan Plateau from GMS-5 water vapor channel data

The brightness temperature of the Geostationary Meteorological Satellite (G MS) -5 water vapor channel (Tb-6.7) and relative humidity, precipitable wat er, specific humidity and temperature observed by radiosondes over the Tibe tan Plateau are compared for the summer of 1995. A wavelength of 6.7 mum wa s employed, so most of the radiation sensed by the satellite comes from the atmospheric layer between 300 and 600 hPa. The plateau altitude is 3,000 t o 4,000 m, and GMS-5 Tb-6.7 over the Plateau represents the moisture inform ation above that. The regression equations of upper tropospheric humidity ( UTH) and precipitable water with Tb-6.7 are presented in this paper. The re lationships between Tb-6.7 and observed temperature and specific humidity a t the standard pressure levels are then compared to each other. Results sho w that, over the Plateau, Tb-6.7 is sensitive to the moisture information a round 200 to 300 hPa height. The results demonstrate that Tb-6.7 is useful for not only qualitatively analyzing the moisture transporting field over a nd around the Tibetan Plateau, but also quantitatively inferring UTH and pr ecipitable water above 100 hPa (W-400). Estimates of W-400 for July and Aug ust 1995 and its diurnal variability over and around the Tibetan Plateau ar e presented.