Satellite image theory Flashcards
Satellite imagery can assist in weather analysis in several ways:
Coherent view of cloud patterns
Pressure patterns and other chart features can be inferred
Identify and follow mesoscale systems which might have been missed.
During the briefing satellite imagery is:
An excellent visual aid
Fills in data sparse areas
Real time information
update analyzed charts of changing conditions
For forecasting satellite imagery is:
an analysis tool
A direct aid in short term forecasting
Input into weather prediction models
A means for monitoring performance in the early stages of a forecast.
List the 2 types of satellite systems
GOES - geostationary
POES - polar orbiting
With respect to GOES, For North America, image scans are produced every __ minutes and a full earth disk is scanned every ____ hours
15 mins
3 hours
How many images of a certain area does the POES satellite take in 12 hours?
1
What are the 2 types of radiation measured by satellite radiometers
Solar (visible)
Terrestrial (infrared)
What are black bodies?
Substances which absorb all radiation falling on them at every wavelength. all liquids and solids are considered black bodies for met.
The maximum intensities of Solar and Terrestrial radiation are:
Solar = 0.5 Micrometers Terrestrial= 11 micrometers
Water vapor absorbs radiation at what wavelengths
6-7 micrometers
What are the factors that effect sensor resolution
Radiation intensity
Distance from source
Radiometer characteristics
Distance from sub point
What is image resolution
number of kilometers per pixel. for GOES it is:
Vis 1
IR 4
WV 8
List the 4 spectral bands used by nav canada
IR
Near IR
Water Vapor
Visible
What is the basic interpretation of VIS images
Black: Low Albedo
White: High Albedo
Clouds with high albedo have:
Large vertical depth
High cloud-water content
Small average cloud-droplet size
What are the advantages of visible imagery
Generally unambiguous representation
Similar to a black and white photo
Important for daytime cloud and surface mapping
Brightness proportional to solar reflection
atmosphere is transparent to this radiation
Image can be enhanced to bring out fringe areas
What are the disadvantages to visible imagery
Daylight hours only
diurnal and seasonal variations
Surfaces with similar albedo difficult to distinguish
What are the advantages to NIR imagery?
Same as visible
Better for high albedo/warm vs low albedo/cold
good for land/water differentiation
What are the disadvantages to NIR imagery?
Only available from POES
Same as visible
The appearance of the Water Vapor imagery depends on?
The temperature of the moisture (or its altitude)
Moisture concentration
Black =high temp low concentrations
white = low temp/high concentrations
What are the advantages of Water vapor imagery?
Good representation of moisture in mid/high levels
mid/high level circulation
cold upper lows, jet streams, deformation zones
What are the disadvantages of Water vapor imagery?
Coarse resolution (8km)
difficult to interpret moisture height
surfaces with similar grey tones difficult to interpret
low water vapor concentrations semi transparent
Only on GOES
What is the IR display radiation?
10.7 micrometers
What do white and black mean on the IR imagery?
White = low temperatures = high clouds, convective tops black = high temperatures = ocean, ground, low cloud
What are the advantages of IR imagery?
Provides temperature representation
Available day or night
important for day and night cloud and surface mapping
Atmosphere transparent to this wavelength
What are the disadvantages of IR imagery?
surfaces with the same temperature impossible to distinguish
Misinterpretations with thin or scattere clouds due to contamination
nonenhanced images difficult to interpret
4km resolution
All satellite images received by Nav Canada contain up to ______ shades of grey. the human eye can only perceive _______
256
15-40
Define image enhancement
The process of assigning new values to a range of pixels in order to more easily identify phenomena.
How many enhancement curves are available for VIS and IR imagery?
VIS = 19 IR = 48
All GOES images originate from?
All POES images originate from?
GOES = CMC POES = Edmonton
