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Modeling attenuation and phase of radio waves in air at frequencies below 1000 GHz
Author(s) -
Liebe Hans J.
Publication year - 1981
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs016i006p01183
Subject(s) - attenuation , water vapor , earth's magnetic field , environmental science , radio wave , computational physics , polarization (electrochemistry) , haze , atmospheric sciences , meteorology , physics , optics , magnetic field , chemistry , quantum mechanics
Moist air is characterized for the frequency range 1–1000 GHz as a nonturbulent propagation medium described by meteorological parameters. An adequate spectroscopic data base for air consists of three terms: (1) resonance information for 29 H 2 O lines up to 1097 GHz and 44 O 2 lines up to 834 GHz in the form of intensity coefficients and center frequency for each line; (2) an empirical water vapor continuum spectrum; and (3) a liquid water attenuation term for haze and cloud conditions. This data base is the heart of two computer programs which calculate and plot attenuation rates (in decibels per kilometer), refractivity (in parts per million), and refractive dispersion (in parts per million). The first covers the troposphere and requires pressure, temperature, and relative humidity as input data. The second addresses isolated line behavior in the mesosphere wherein the geomagnetic field strength H is an additional input parameter due to the Zeeman effect of the O 2 molecules. Each oxygen line splits proportionally with H into numerous sublines, which are juxtaposed to form Zeeman patterns spread over a megahertz scale. Patterns of three main polarization cases are considered. Various typical examples for a model atmosphere demonstrate the utility of the approach, provide new information, and underline the serious role that water vapor plays above 120 GHz.