Visible and Infrared Imaging Radiometer Suite (VIIRS) instrument onboard the
National Polar-Orbiting Operational Environmental Satellite System (NPOESS), now
called the Suomi National Polar-Orbiting Partnership (NPP) space platform.
Although it has a coarse spatial resolution (approximately 0.39 km), VIIRS bears
mention because it has four TIR spectral bands and it extends and improves upon a
series of measurements initiated by the NOAA Advanced Very High Resolution
Radiometer (AVHRR), which has been used in many past and present studies of land
surface energy balance fluxes. NPP collects data at about 1:30 PM and 1:30 AM local
time, similar to the temporal cycle of Aqua. More information on NPOESS/VIIRS is
available at http://npp.gsfc.nasa.gov/index.html.
It must be noted that NASA or NOAA Earth-observing satellites are not the only
space-based TIR platforms. The European Space Agency (ESA), the Chinese, and
other countries have in orbit or plan to launch TIR remote sensing systems. However,
a discussion of these systems will not be presented here for the sake of brevity.
2
3.3 USE OF TIR DATA IN ANALYSIS LANDSCAPE ECOLOGICAL
CHARACTERIZATION
Solar and thermal radiation within the Earth–atmosphere regime governs the energy
available at Earth’s surface for heating and cooling of the air (i.e., sensible heat), the
evaporation of water from soil and vegetation (i.e., latent heat), and heating or cooling of
natural (e.g., soil) and nonnatural (e.g., pavement) land surfaces. Earth’s only significant
source of energy is solar radiation, which is partitioned into various energy fluxes at the
surface (Diak et al., 2004). The ultimate driving factor controlling surface characteristics
such as soil moisture, land cover, and vegetation conditions is the energy transfer that
occurs in land–atmosphere interactions. The simplest form of the surface energy balance
(assuming no advection of energy across the land surface) is given by
R net = G + H + LE
(3.1)
where R net is the net radiation balance, G refers to the soil heat flux (i.e., the energy used
to warm the near-surface soil layers), H is the sensible heat flux, and LE is the latent
heat flux. The ability to quantify the partitioning of available energy at the land surface
into sensible and latent heat flux is key to understanding the impact of the land surface
on atmospheric processes (Czajkowski et al., 2000). Understanding land–atmosphere
energy exchange processes is important for improving short-term meteorological
conditions (i.e., the weather) and in predicting the impacts of natural and anthropogenic changes in the land surface on long-term climate variability (Humes et al., 2000).
Although land–atmosphere energy fluxes can be measured using in situ methods via
surface thermal radiation measurements and soil moisture instruments, the synoptic
view provided by remote sensing data from satellites can measure land surface
2 Quattrochi et al. (2003) give a listing of the characteristics of U.S. and international imaging satellites
either launched at that time or planned for future launch.
USE OF TIR DATA IN ANALYSIS LANDSCAPE ECOLOGICAL CHARACTERIZATION
37
National Polar-Orbiting Operational Environmental Satellite System (NPOESS), now
called the Suomi National Polar-Orbiting Partnership (NPP) space platform.
Although it has a coarse spatial resolution (approximately 0.39 km), VIIRS bears
mention because it has four TIR spectral bands and it extends and improves upon a
series of measurements initiated by the NOAA Advanced Very High Resolution
Radiometer (AVHRR), which has been used in many past and present studies of land
surface energy balance fluxes. NPP collects data at about 1:30 PM and 1:30 AM local
time, similar to the temporal cycle of Aqua. More information on NPOESS/VIIRS is
available at http://npp.gsfc.nasa.gov/index.html.
It must be noted that NASA or NOAA Earth-observing satellites are not the only
space-based TIR platforms. The European Space Agency (ESA), the Chinese, and
other countries have in orbit or plan to launch TIR remote sensing systems. However,
a discussion of these systems will not be presented here for the sake of brevity.
2
3.3 USE OF TIR DATA IN ANALYSIS LANDSCAPE ECOLOGICAL
CHARACTERIZATION
Solar and thermal radiation within the Earth–atmosphere regime governs the energy
available at Earth’s surface for heating and cooling of the air (i.e., sensible heat), the
evaporation of water from soil and vegetation (i.e., latent heat), and heating or cooling of
natural (e.g., soil) and nonnatural (e.g., pavement) land surfaces. Earth’s only significant
source of energy is solar radiation, which is partitioned into various energy fluxes at the
surface (Diak et al., 2004). The ultimate driving factor controlling surface characteristics
such as soil moisture, land cover, and vegetation conditions is the energy transfer that
occurs in land–atmosphere interactions. The simplest form of the surface energy balance
(assuming no advection of energy across the land surface) is given by
R net = G + H + LE
(3.1)
where R net is the net radiation balance, G refers to the soil heat flux (i.e., the energy used
to warm the near-surface soil layers), H is the sensible heat flux, and LE is the latent
heat flux. The ability to quantify the partitioning of available energy at the land surface
into sensible and latent heat flux is key to understanding the impact of the land surface
on atmospheric processes (Czajkowski et al., 2000). Understanding land–atmosphere
energy exchange processes is important for improving short-term meteorological
conditions (i.e., the weather) and in predicting the impacts of natural and anthropogenic changes in the land surface on long-term climate variability (Humes et al., 2000).
Although land–atmosphere energy fluxes can be measured using in situ methods via
surface thermal radiation measurements and soil moisture instruments, the synoptic
view provided by remote sensing data from satellites can measure land surface
2 Quattrochi et al. (2003) give a listing of the characteristics of U.S. and international imaging satellites
either launched at that time or planned for future launch.
USE OF TIR DATA IN ANALYSIS LANDSCAPE ECOLOGICAL CHARACTERIZATION
37