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Measures R.M. Laser remote sensing (1992)(600dpi)(T)(524s)_EO_.djvu |
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received by a 0.4-mm-radius, detector is plotted as a function of range F for
Lidar Equation
ю3 ю4
RANGE, R(m)
Fig...
It should also be noted that a small detector has the added advantage of a
small inherent noise level...
LASER-REMOTE-SENSOR EQUATIONS
to the location of some monitor of ft):
In the case of long-range work with a lidar system that is well aligned
(8 « 0), we saw earlier (Section 7.4) that A(R) « Ao, so that
S(R) - S(R«) - Ц^у} "//(*) « G.96)
and this difference in the S-values only depends upon the atmospheric-depen-
atmospheric-dependent factors...
Fluorescence, Raman, and DAS lidar signals versus range for sulfur dioxide (Measures
and Pilon, 1972)...
The value of the spectral rejection ratio required for Raman scattering is in
general very small...
R) = EJ(X)^p-N(R)a-^^-%•-?«*><* (8.10)
where we have also used equations G.12) and G.22), and oR(XL, X) is taken as
the appropriate Raman scattering cross section for the molecule of interest...
This assumption is tantamount to stating that N(R)aA(X0)
:» /с(Л0, R) at the point of interest...
LIDAR ERROR ANALYSIS
Any quantitative measurement has errors and uncertainties associated with it...
Error Analysis for Elastic-Backscattering Lidar
The role of aerosols and particulates in our climate is known to be important...
We may thus write
v2
+ьв1
The form of equation (8.59) presupposes that no correlation exists between the
variables n9 x9 q9 and 2?#, due to their different methods of evaluation...
In addition, there are a number of situations in which the
concentration of the fluorescing agent is sufficiently high that laser-induced
fluorescence is still attractive...
Although
virtually all molecules possess strong, electronic absorption lines, very few of
them have such features at wavelengths long enough (Section 4.5) for them to
be accessible to laser probing within the atmosphere...
It is evident from equation (8.83) that we are assuming a negligible error in the
differential absorption cross section, in the coefficient рл, and in the noise
power Pn...
As
we have indicated, dial measurements in the infrared are viewed as an
important area of growth, due to the large selection of molecules having
suitable vibrational-rotational absorption bands in that part of the spectrum...
In order to reduce equation (8.123) to a more manageable form we shall use
the following expansion:
(8.126)
and also assume that X, is selected to coincide with the center wavelength for
absorption:
X, = X^ (8.127)
At the same time we shall assume that X2 is sufficiently detuned from the
absorption line center that
я 0 (8.128)
over the wavelength interval, X2 — AX0/2 < X < X2 + ДХ0/2...
No attempt has been made to summarize the vast literature of atmospheric
lidar measurements within this chapter...
) and lends
itself to a much better method of long-range concentration mapping through
differential absorption and scattering (Schotland, 1966)...
This determination of the H2O absorption for each dye-laser pulse
eliminates a major source of uncertainty in such dial measurements...
T(zx) is often estimated and T(z) calculated step by step
downward from zv The value of Tx rapidly becomes a little consequence...
The ratio of the resulting
intensities is, in principle, solely dependent upon the gas temperature...
Equation (9.16) can be converted into a relation for the
temperature !Tin terms of the reference temperature To:
T=Tn{l...
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