Remote-Sensing Technologies and Data Processing Algorithms - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 177

trajectory. The inverse task consists in the determination of the atmosphere and
ionosphere parameters through experimental data describing the signal variations.
The method of atmosphere radio-translusense can be used when the microwave
emission receiver is sited on the Earth

is surface. Using the Doppler effect on
wavelength 1.35 cm (22.235 GHz) in this case allows the vertical distribution of
water vapor in the uppermost atmosphere to be received with acceptable precision.
Atmospheric microwave sensing can be expanded to consider the possibility of
estimating a wider set of its parameters. To do so would mean solving a complex
mathematical task connected with the prognosis of the microwaves relaxation
according to sensing routes in the atmosphere. Millimetre range causes special
interest in this respect. According to the investigations by Meriakri (1992) and
Strelkov (1995) many gases have discrete absorption spectre in the waves of mil-
limetre and submillimetre ranges. This allows the average concentration of the gas
component along the sensing route to be calculated based on estimating electro-
magnetic wave absorption. An example of such a calculation is given in Table 2.20 .
A special feature of the millimeter range is the possibility to form narrowly
directed radio-bundles because of the relatively small apertures of the emitters. The
task of atmosphere parameter estimation can be transformed to registering varia-
tions in signal relaxation on the sensing route between the receiver and transmitter
followed by solving a suitable integral equation that takes into account the
refraction of electromagnetic waves in the troposphere, cross-diffraction of signal
bundles, and possible variations in the vertical distribution of refraction indicators
along the route. Monitoring systems of low atmosphere also call for the in

'

uence of
land covers on the propagation of millimeter waves to be taken into consideration.
Millimetre and submillimetre ranges under the using of active and passive
sensing regimes ensure the reliable estimation of content in the atmosphere of
certain chlorine compounds, carbon oxide, nitrogen dioxide, ozone, and water
vapors, as well allow to determine the wind spead and temperature (Strelkov 1995,
1996). The prospect of these ranges bringing about bi-static radio-translusense of
the atmosphere is down to the moderate price of

fl

field measurements and existing
theoretical results concerning the methodologies used to reconstruct atmospheric
spatial distribution parameters along observational routes.

Table 2.20 Calculation of the gases concentrations basing on the measurements of signal
relaxation at the frequence ʽ a on the atmosphere trace of 10 km (Meriakri 1992)

Gas concentration (mg m − 3 ) Atmosphere relaxation (db km − 1 )

Gas ʽ ʱ ( ʜʗ z)

CO 1,500 0.3 115.271

330 6 235.789

N 2 O 1,600 0.2 100.492

240 6 351.666

SO 2 2,300 0.2 104.029

560 0.4 135.696

H 2 S 9 1.8 168.763