Analysis of the application of the optical method to the measurements of the water vapor content in the atmosphere – Part 1: Basic concepts of the measurement technique

摘要

We retrieved the total content of the atmospheric water vapor (or IntegratedWater Vapor, IWV) from extensive sets of photometric data obtained since1995 at Lindenberg Meteorological Observatory with star and sun photometers.Different methods of determination of the empirical parameters that arenecessary for the retrieval are discussed. The instruments wereindependently calibrated using laboratory measurements made at PulkovoObservatory with the VKM-100 multi-pass vacuum cell. The empiricalparameters were also calculated by the simulation of the atmosphericabsorption by water vapor, using the MODRAN-4 program package for differentmodel atmospheres. The results are compared to those presented in theliterature, obtained with different instruments and methods of theretrieval. The reliability of the empirical parameters, used for the powerapproximation that links the water vapor content with the observedabsorption, is analyzed. Currently, the total (from measurements,calibration, and calculations) errors yield the standard uncertainty ofabout 10 % in the total column water vapor. We discuss the possibilitiesfor improving the accuracy of calibration to ~1 % as indispensablecondition in order to make it possible to use data obtained by opticalphotometry as an independent reference for other methods (GPS,MW-radiometers, lidar, etc).