last update: 11 May 2016
3. Comparison of different methods and apparatus for measuring the gases composition of the atmosphere
At Atmospheric Remote Sensing Laboratory different methods and apparatus are used for measuring the atmospheric gaseous composition (Table in Fig. 3.1). Therefore one of the main research problems – comparisons of various methods and the equipment for measurements of atmospheric gaseous composition, determination of the information content and errors of various measurements and their mutual calibration.
3.1. Comparison of ground-based measurements of the total water vapor
Water vapor is the major natural greenhouse gas in the atmosphere of Earth. Its contribution to greenhouse effect can reach 60% and more. There are many local and remote methods of measurements of water vapor content. Their variety is connected with large variability of the water vapor content in the atmosphere, high requirements to the accuracy and spatial resolution of measurements, and also large range of temperatures and pressures with which it is necessary to measure his contents. Now it is important to estimate errors of measurements by various methods and to carry out their mutual calibration. In Fig. 3.2 seasonal variations in the water vapor total content (TC) retrieved from ground-based FTIR measurements in Peterhof (1) and from radio sounding in Voyeykovo (2) are represented.
In St.-Petersburg State University the wide program of comparisons and mutually calibrations of the following methods of measurements of water vapor TC is carried out:
1. Ground-based IR spectroscopic method.
2. Ground-based method using the CIMEL spectrophotometer.
3. Microwave ground-based method (downwelling thermal radiation).
4. Radio refraction method.
5. Radiosonde method.
6. Microwave satellite method.
Besides data of meteorological measurements and forcasts are also attracted for the analysis.
1. Semenov A.O., Ya.A. Virolainen, Yu.M. Timofeyev, and A.V. Poberovskii, 2015: Comparison of GroundBased FTIR and Radio Sounding Measurements of Water Vapor Total Content. Atmospheric and Oceanic Optics, 28, 2, 121–125.
2. Berezin I. A., Ya. A. Virolainen, Yu. M. Timofeyev, and A. V. Poberovskii. 2016: Comparison of IR and MW Ground-Based Measurements of Total Precipitable Water. Izvestiya, Atmospheric and Oceanic Physics, 52, 3, 253–256.
3.2. Comparisons of total ozone measurements
Measurements of total ozone (TO) are performed by ground-based IR and MW methods. In the first method, measurements of direct solar IR radiation spectra with high spectral resolution are used, and in the second one – measurements of brightness temperatures of MW downward radiation. Besides, TO measurements at Peterhof are compared with those at Voeikovo and different satellite measurements. Comparisons of TOs measured by M-124 photometer, IR method and Dobson spectrophotometer are given in Fig. 3.5.
1. Virolainen Ya. A., Yu. M. Timofeev, D. V. Ionov, A. V. Poberovskii, and A. M. Shalamyanskii, 2011: Ground-Based Measurements of Total Ozone Content by the Infrared Method. Izvestiya, Atmospheric and Oceanic Physics, 47, 4, 480–490.
2. Virolainen Ya. A., Yu. M. Timofeev, A. V. Poberovskii, 2013: Intercomparison of Satellite and GroundBased Ozone Total Column Measurements. Izvestiya, Atmospheric and Oceanic Physics, 49, 9, 993–1001.