Final Flashcards
What does satellite data offer?
cost-effective, timely, transparent, information on crop type, plant health, stress, and productivity
What are early forecasts?
Critical
Crop Monitor for AMIS
develop transparent, timely, crop condition assessments in primary agricultural production areas highlighting potential hotspots of stress/ bumper crops
NASA’s Earth Observation for Food Security and Agriculture Consortium
increase food security awareness and understand of the applications of NASA’s and other satellite data products by users from a wide range of sectors
Major tasks of (4)
crop state assessment
crop yield assessment/ forecasting
crop type mapping
crop area estimation
Biophysical Parameters
total canopy chlorophyll, vegetation fraction, fraction of photosynthetically active radiation absorbed by photosyhntetically active vegetation, green leaf area index, gross primary production
information retrieval
spatial: courier transformation
spectral: spectral curvatures
Temporal: change detection, temporal profiles
Spectral curve of plants
typical vegetation reflectance curve with dominant factors controlling leaf reflectance
spectral curve of plants:PROSPECT
radiative transfer model that represents the optical properties of plant leaves from 400nm to 2500nm
simulates spectra based on input parameters of the plants
inverse problem
to estimate properties of the plants based on the given spectra
Chlorophyll content
relates closely to the crop primary production and is a good indicator of the physiological status and the carbon sequestration potential of crops, it is also a good predictor of crop yield
Vegetation fraction
defined as the percentage or fraction of occupation occupation of vegetation canopy in a given ground area in vertical projection
Leaf Area Index
the ratio of the one-sided green leaf area to the ground area underneath
Fraction of Absorbed Photosynthetically Active Radiation
influences vegetation production
Gross Primary Production
vegetation productivity is the basis of all the biosphereic functions on the land surface and is simply defined as the production of organic matter through photosynthesis
Crop type mapping
classification of multi-temporal multi-spectral satellite images into crop-related classes
cropland vs non-cropland
training/ calibration data: ground truth
soil moisture
soil moisture is the water that is held in the space between soil particles
what does soil moisture depend on
soil properties
topography
presence/ absence of vegetation
the frequency and amount of precipitation/ irrigation
soil moisture
SMAP: soil moisture Active Passive
What are the mapping key parameters from remote sensing?
Land surface albedo
downward shortwave radiation
land surface temperature
What are the determine factors for remote sensing?
surface- reflectance, emissivity, and temperature
Atmosphere
what are sensor characteristics?
Wavelength- spectral signature
view geometry- angular signature
polarization etc
inversion problem
Underdetermined
Ill-posed/ improperly posed problem
Albedo
ratio between reflected solar radiation and incident solar radiation
What direction in albedo in?
all directions and it is broadbanded
What direction is RS signature in?
One direction
Narrow banded
BRDF what does it stand for?
Bi-directional Reflectance Distribution Function
What is BRDF
Ratio of incremental radiance, leaving surface through an infinitesimal solid angle in direction to incremental irradiance from illumination direction
How are BDRF and albedo related?
Albedo depends on BRDF and incident angle
BRDF modeling in…
radiative transfer models: physical explanation
canopy/ soil parameters
empirical models
empirical models: kernel-driven models
Albedo Retrieval approaches
BDRF fittings, optimization, direct estimation, and BRDF database
What are needed for BDRF fittings?
Multiangular RS data: MISR, POLDER
3 observations
temporal composite approach- assume no surface change
to measure BRDF via RS you need?
multiple cameras on same platform
ex: multi-angle imaging spectroRadiometer
broad swath with large overlap so multiple orbits build up multiple view angles
Pointing capability: offers an oblique viewing capacity, the viewing angle is adjustable through 27 degrees off vertical
Issues of BRDF fitting approach
error propagation
unable to capture rapidly changing albedo
large errors over snow albedo
Unique features of NOAAs VIIRS land surface albedo product
high accuracy, gap-free, high temporal resolution, daily mean value
Incident Solar Radiation
aka insolation
300nm - 3000nm
drives longwave emission, latent and sensible heat fluxes
one of the key parameters in earth surface radiation budget
Photosynthetically active radiation
400nm-700nm
an essential input for most of the ecosystem models
important for quantifying earth’s carbon cycle
Radiation transfer modeling
accuracy dependent on quality of input data
requiring inputs of atmospheric and surface parameters
computationally expensive
Parameterization
approximation of RT models
Efficient
Summary of forward methods
highly accurate when high quality atmospheric input variables are available
Innovative LUT-based method
accurate and efficient
Directly use TOA radiance data
improved spatial resolution
two parameterization schemes
TOA radiance and Surface flux
Parameters are pre-calculated from accurate MODTRAN
Steps of the algorithm using temporal signatures
a set of temporal observations for each pixel
covert blue-band TOA radiance to “surface reflectance” using a default clear atmosphere
identify a set of “clear” observations with the minimum blue-band reflectance
interpolate surface reflectance of other observations
interpolate surface reflectance of other observations
Algorithm integration
individual retrieval methods have strengths and limitations
using machine learning methods to combine multiple retrieval algorithms
Skin temperature retrieval approaches
sea surface temperature vs. land surface temperature
single channel algorithm
two channel algorithm
q
q
q
q
q
