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THE
ATMOSPHERIC FILTER
VOLUME I - SOURCES / VOLUME 2 - EFFECTS
by W. Michael Farmer
The atmosphere acts like an optical filter
that affects visual, infrared, and millimeter
wave propagation. The atmospheric filter
decreases image contrast and resolution.
It reduces measured signal intensity for
laser, radar, and non-imaging/radiometer
systems. The effects of atmospheric filter
sources depend on spectral band and the
sensor type used to acquire data. The filter
impacts sensor design, data acquisition,
and data interpretation.
Engineers and technicians are provided
the information necessary to understand
and quantify sensor response. Meteorologists
are provided guidance on the importance
of instrument placement and measurement
accuracy when performing remote sensing
measurments. Students have access to a wide
range of detailed information that supports
their early entry into effective experimental
design, data acquisition, and remote sensing
data analysis.
Numerous approximations are used throughout
both volumes. These provide valuable insights
into, and a useful working knowledge of,
the relationships between meteorology, the
atmospheric filter, and remote sensor performance.
VOLUME I - SOURCES
Volume I describes the atmospheric filter,
its components, and its effects on remote
sensors. Detailed texts supported by extensive
figures illustrate the complex relationships
that exist. The primary atmospheric gases,
their concentration, absorption bands, and
meteorological effects are discussed. Aerosol
scattering and absorption properties are
part of the atmospheric filter. Approximations
are used to develop explicit expressions
for computing aerosol spectral properties.
Detailed examples of multi-modal dust size
distributions for mixtures of dust grain
size distributions and mineral types are
provided. Gases, aerosols, and dusts have
spectrally varying effects and therefore
affect instrument performance differently.
Detection of a distant target, radiometer
data, and optical beam propagation depend
upon the path length, atmospheric constituents,
and spectral response of the sensor.
The physical properties of liquid, frozen,
mixtures of precipitation, and fogs affect
their radiometric properties. Examples of
liquid water and ice effects on millimeter
wave propagation are developed. Methods
for classifying and measuring frozen precipitation
are discussed. Case studies illustrate the
effect of fog on remote sensors. The variation
of fog characteristics with altitude is
included.
108 figures, 20 tables, 94 references,
274 + xii pages (2001)
VOLUME II - EFFECTS
Meteorological conditions determine the
dynamics and spatial variability of atmospheric
filter sources. These conditions are characterized
by solar position, cloud cover, visual range,
spectral transmittance, wind, natural radiation,
and atmospheric stability. Natural radiation
affects visual and infrared system performance
differently. Passive remote sensor models
include visual band imaging systems, the
human eye, and thermal band imaging systems.
The human observer's perception is quite
different than other remote sensor outputs.
What you can see is not necessarily the
same as what you measure. Both active and
passive systems are explained in detail.
Models for transmissometers and LIDAR systems
are presented.
138 figures, 18 tables, 71 references,
336 + xxiv pages (2001).
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