1. Representing Climate Data II
Satellite Imagery and Radar

2. BRING GLOBE TO CLASS, PAT.

4. Radiometers electronic sensors
Detect radiation from atmosphere, clouds, surface
Can sense specific wavelengths of radiation
“spectral signatures” of gases
Scans surface
Scans continuously adjacent squares arranged in scan lines
Sweep: length of scan line

5. 1. Geostationary
At altitude of 36,000 km (22,240 mi), orbit of satellite matches earth’s rotation
Satellite is moving at same speed earth is rotating so it appears to stay in one spot and always sees the same place on earth
Centered on a particular longitude where it intersects equator

6. Geostationary Advantage: Real time data
Disadvantage: distorts polar regions

10. GOES
Full disk

11. Polar-orbitting Follows parallel meridian lines
Altitude 850 km (540 mi)
Passes poles on every revolution
Earth rotates eastward and satellite scans successive passes
Advantage:
Better coverage of high latitudes

14. polar-orbitting

15. Brand New GOES east and west satellites
March 2018

16. Geostationery Operational Environmental Satellite (GOES)
Built by NASA
Taken over by NOAA once they get into orbit;
As technology improves, old satellites are decommissioned and new ones are launched.

17. changing of the (satellite) guard
GOES-P
GOES-15
March 4, 2010
Remains in service in tandem with GOES-17 through early July 2019 to allow for assessment of GOES-17 as operational GOES West
GOES-R
GOES-16
November 19, 2016
In operation as GOES East
GOES-S
GOES-17
March 1, 2018
In operation as GOES West

18. Types of weather images:
1. Visible 2. Infrared satellite 3. Water Vapor 4. Radar

19. GOES now offers 16 band channels

20. 1. visible Detects visible wavelengths.
Reading shortwave reflected by earth, ocean, clouds
(albedo)
Daytime only

22. Albedos of various surfaces:
Earth’s surface (31%)
Cumulonimbus clouds 0.9 (90%)
Stratocumulus clouds 0.6 (60%)
Cirrus clouds (40 – 50%)
Fresh snow 0.8 – 0.9 (80 – 90%)
Melting snow 0.4 – 0.6 (40 – 60%)
Sand – 0.35 (30 – 35%)
Grain crops – 0.25 (18 – 25%)
Deciduous forest – 0.18 (15 – 18%)
Coniferous forest – 0.15 (9 – 15%)
Tropical rainforest 0.07 – 0.15 (7 – 15%)
Water bodies – (6 – 10%) increases at low sun angles

23. Visible imagery High vs. low albedo : High albedo: lighter
Cloud tops, snow, ice
Low albedo: darker
Land, ocean
Cloud thickness
Thicker cloud cover is more reflective: brighter
Cloud height (IR better)
Cumulonimbus : very bright white
Low : bright
High (cirrus) : not- bright white

26. Notice that visible imagery records radiation that passes through
atmospheric window.

27. New GOES East visible bands
Band 1 centered on 0.47 µm VISIBLE ( “blue” band) Good for seeing aerosols (dust, haze, smoke , clouds) Band µm VISIBLE (“red” band) Good for seeing snow/ice on surface; smoke, volcanic ash, hurricanes

29. Husky refinery explosion, Superior WI April 2018
Satellite images

30. 2. Infrared
Detects IR
Clouds, land, ocean, snow/ice reflect visible but emit IR
(visible imagery records reflected shortwave; IR records emitted IR)

32. A blackbody is a perfect absorber of all the radiation it receives and emitter of max radiation possible at a given temp

34. Thermal Infrared imagery
Detects temperature
Low temperatures: lighter shades of gray
High temperatures: darker shades of gray
Cloud Heights:
Low clouds warmer than high clouds
Low clouds: dark
High clouds: light
Cumulonimbus clouds: bright white
Can record at night
IR images are often color-enhanced to highlight temperature differences

36. visible

37. Infrared (IR)

38. Enhanced IR

40. GOES bands
A bunch of IR bands!!!!
Band 11
8.4 µm THERMAL IR “cloud-top phase”
distinguishes ice clouds (high, cold) from water droplet clouds (low, warm)

42. Band µm “clean IR window” THERMAL IR Doesn’t have as much interference from water vapor Cloud heights (or any other use that requires temp/heat differences)

46. Cool ! New ! GOES East bands Near IR : daytime only (see next slide)
Band 3 centered on 0.86 µm ( “veggie” band) NEAR IR Good for seeing cirrus clouds, daytime clouds, fog, aerosols and can be used to distinguish different types of vegetation Band µm (“ cirrus” band) NEAR IR Good for seeing thin, high cirrus clouds during daytime; Can see upper level tropospheric things like volcanic ash plumes; Doesn’t see low level troposphere where there is a lot of water vapor because this is a band that is absorbed by water vapor

47. A blackbody is a perfect absorber of all the radiation it receives and emitter of max radiation possible at a given temp

48. 1.37 µm

50. Veggie Band

51. 3. water vapor Visible and IR images:
Record radiation transmitted through atmospheric windows
Water vapor images:
record IR emitted by water vapor in the atmosphere
Water vapor absorbs and emits IR at μ

52. 6.7 – 7.3 µ

54. Does NOT detect water vapor in LOWER troposphere
Because it will be absorbed by water vapor at higher altitudes and therefore will not go out to space to be recorded by satellite

55. b) If upper troposphere is dry, any radiation detected will be coming from MIDDLE troposphere lower=warmer=relatively darker gray c) If upper troposphere is wet, radiation detected is from HIGH (cold) water vapor higher = colder = relatively brighter gray/white (movement of water vapor indicates upper and mid tropospheric winds)

57. Enhanced IR of same time period

59. Enhanced IR of same time period

60. Water vapor images can also be color enhanced

65. Hurricane Florence

66. Water Vapor Images are useful for:
Tracking moisture (at mid and upper levels)
Locating Low pressure / storm centers
Identifying the jet stream location
Can see rising and sinking air regions

67. NOAA website
GOES site

68. 7.3µ
Low mid-tropospheric
Water vapor
6.9 µ
Mid mid-tropospheric
Water vapor
6.2 µ
Upper tropospheric
Water Vapor

69. REVIEW Geostationary and polar-orbiting satellites
Visible satellite imagery:
Records albedo
Only useful during daylight hours
Shows cloud cover, land/water, frontal systems, snow surfaces
Infrared satellite imagery:
Thermal
Records emitted IR
Records day and night
Detects temperature
Reads cloud height
Near
Daytime only
Veggie Band (not lower troposphere because water vapor absorption)
Cirrus Band

70. Water vapor satellite imagery:
Records infrared at 6.7 – 7.3 µ emitted by water vapor
Cannot use for lower atmosphere near surface
Tracks moisture
Shows storm (low) centers
Shows jet streams and sinking air

77. 4. radar (Radio Detection and Ranging)
look inside of clouds
Now use microwaves instead of radio waves
RADAR stands for RAdio Detection And Ranging and was slowly developed over time starting way back in the late 1800s. By the start of World War II, many countries used it to detect enemy ships and aircrafts. When radar operators discovered that precipitation caused 'false' echoes on their screen (masking potential enemy targets) they realized the new found potential of radar. Soon after the war surplus radars were used as precipitation detectors.

78. Transmitter sends microwave pulses
Targets scatter energy back to receiver
Amplified and displayed as echo
Time between emitting energy and receiving it back from target tells distance to target

79. Shorter microwave wavelengths (~1 cm)
detect small targets
(e.g., tiny droplets of water in clouds)
Longer micro-wavelengths (3 -10 cm)
detect larger targets
(e.g.,precipitation)
Brightness of echo
Amount of precipitation

80. This morning

84. Doppler Radar Based on principle of Doppler shift:
Waves moving towards observer have different frequencies than waves moving away from observer.
e.g., sound from approaching vs. leaving ambulance
Doppler radar can measure direction
Knowing wind speeds and directions within clouds gives info about vorticity (spin)
By utilizing the Doppler Effect, Doppler radars provide information regarding the movement and positions of targets. After the radar emits a pulse of radio waves, it tracks the phase shift between the transmitted radio wave and the received echo. This phase shift shows whether the target is moving directly toward or away from the radar, called its radial velocity. A positive phase shift implies motion toward the radar and a negative shift suggests motion away from the radar. The phase shift effect is similar to the "Doppler shift" observed with sound waves. If an object emits sound waves as it approaches a location, the waves are compressed leading to a higher frequency. As the object moves away from a location, the sound waves are stretched leading to a lower frequency. This is often experienced when an emergency vehicle drives past with its siren blaring.

85. 158 Doppler stations in US

87. The radar dish can rotate 360 degrees in the horizontal and approximately 20 degrees in the vertical. As the radar antenna turns, it emits extremely short bursts of radio waves, called pulses and waits for these pulses to return during the "listening period". Each pulse lasts about seconds with a "listening period" of second. The transmitted radio waves move through the atmosphere at around the speed of light. Once it hits a target such as a raindrop or snowflake, the radio waves are scattered with some of the energy returning back to the radar. Radar observes all of this information during the “listening period” with the process repeated up to 1,300 times per second. Observing the time it takes the radio waves to leave the antenna, hit the target, and return to the antenna, the radar can calculate the distance and direction of the target using the “Doppler effect” (hence the title Doppler radar). In addition, the returned energy the radar receives provides information on the target’s characteristics including size, intensity and with the newest Dual Polarized radars, even precipitation type.
Tour the radome!

88. Makes repeated 360˚scans of atmosphere at increasing elevation angles.
2 modes:
Clear Air mode
No rain
Dust, light snow
VCP 31, 32 (volume coverage pattern)
Precipitation mode
rain

89. Clear Air Mode

90. Precipitation Mode

92. Reflectivity units dBZ : decibels of Z
“Z” is energy reflected back to radar
Values increase with strength of signal
Clear air
Precipitation
dBZ equate to approximate
rainfall rates

93. Ground clutter Ground, buildings, trees, cars Insects Birds Turbulence
Within 25 km of radar
Not moving with respect to radar, so can be detected by radial velocity
Insects
Birds
Turbulence
Effects density

96. Base reflectivity Reflectivity in lowest elevation “slice”
Used to survey area close to radar

97. Composite reflectivity
Combines all elevation scans
Shows highest reflectivity

98. Velocity units Radial velocities in knots Red: wind moving AWAY
Green: TOWARD radar
Need to know where radar is!

100. Vorticity signature, tornado

103. Dual-Polarization radar
Conventional radar receives pulses in horizontal directions.
Dual-pole : horizontal and vertical
Get a better picture of what exactly the targets are: hail, rain, snow, melting snow, insects!
The National Weather Service is currently upgrading their radar network to dual-polarization radars. While conventional radars emit and receive pulses in the horizontal direction, dual-polarization radars go a step further and transmit and receive waves in the horizontal and in the vertical direction. This provides a more complete picture of targets in the atmosphere and finally allowing forecasters to differentiate between rain, snow/melting snow, and even hail.

104. Example of use of dual pole radar: can detect hail

105. Dual pole

106. RIDGE (Radar Integrated Display with Geospatial Elements)
Combine radar with topography, roads, county lines, rivers, warnings
Overlay maps as layers
Toggle layers on or off
GIS compatible
NWS Duluth