A new instrumental approach to water vapor determination based on solar spectroscopy

Abstract

Tropospheric water vapor is of central interest in a large variety of geoscientific fields, such as geodesy, geodynamics, climate research and meteorology. A new instrumental approach to ground-based mapping of tropospheric water vapor has been developed. It is based on high-resolution absorption measurements in the near infrared region by means of a solar spectrometer (SSM). To prove the feasability and accuracy potential of the new technique, a 30 day field experiment was carried out, performing SSM measurements simultaneously with two independent methods. One of them uses the Global Positioning System (GPS). This technique, called GPS meteorology, exploits the high sensitivity of the satellite signals to atmospheric delay for a determination of tropospheric parameters. As a third technique two ground-based microwave water vapor radiometers (WVR) were operated. A comparison of the three different techniques, exploiting absorption-, refraction-, and emission properties of water vapor, respectively, demonstrated the potential of solar spectrometry for precise and absolute determination of PW without meteorological a priori information.