COMPARISON OF TWO MODELS RELATING PRECIPITABLE WATER TO SURFACE HUMIDITY USING GLOBALLY DISTRIBUTED RADIOSONDE DATA OVER LAND SURFACES

Abstract

Relationships between precipitable water (W; mm) and surface vapour pressure (e0; hPa), and surface dew point temperature (td; °C) are evaluated using mean monthly radiosonde data for 24 months at 45 globally distributed locations both for individual locations and for the pooled data from all locations. The data selected cover a wide range of climatic conditions and complete seasonality for most of the locations. The physical basis of the models relating W to e0 or td is reviewed briefly. Two semi-empirical models, namely, W=C1e 0+C2 and ln W=C3td+C4, gave highly significant correlations both for individual locations and for the pooled data (r2 =0·94, C1=1·70, C2=−0·1, C3=0·058, and C4= 2·42 for the pooled data), but examination of the residuals showed some inadequacy of these models for the pooled data.