1. Summer Session 28 July 2011

4. http://www.itek.norut.no/vegetasjon/fenologi/introduction/ndvi.html

5. Liquid Water Absorption

6. Important things to remember in using VIS/RIR data to monitor water surfaces Pure water absorbs EM energy in most of the IR region Pure, deep (> 50 m) water bodies have low reflectance in the visible and very near IR region of the EM spectrum However, some EM energy in this region is transmitted into the water column, where it reacts with particles suspended in the water column 6

7. Reflection off the bottom in shallow water

8. Variations in image color/intensity in the Bahamas region is due to reflectance off the ocean bottom

9. MODIS Image of Phytoplankton – Bering Sea, Alaska

10. Plankton off of the West coast of Mexico

11. Plankton off of Tasmania, Australia

12. Pyrrophytes (dinoflagellates) Oblique aerial photograph of red tide

13. MODIS Satellite Image of Suspended Sediments Mississippi River Delta

14. Simple model of flux off of a water surface ii  b – reflected from the bottom  s - scattered from water  p - scattered/reflected from particles suspended in water  r - surface reflection

15. What can happen to EM energy reaching a water surface? 1. Reflected off the surface 2. Transmitted into the water column 3. Absorbed by the water 4. Scattered by the water 5. Absorbed by materials suspended in the water 6. Reflected or scattered by matter suspended in the water 7. Reflected off of the bottom

16. Water Attenuation c( ) c ( ) =  ( ) + b ( ) where  ( ) = water absorption coefficient b ( ) = water scattering coefficient

18. Absorption and wavelength Note that wavelengths > 0.9  m have large absorption coefficients Because of this, sea surface remote sensing systems do not have bands > 0.9  m Absorption will change if you have dissolved inorganic or organic material in the water, depending upon the compounds that are dissolved

19. ultrviolet

21. Role of suspended sediments Suspended sediments in the water column do two things 1. Absorb/transmit EM energy 2. Scatter/reflect EM energy

22. Simple model of flux off of a water surface ii  s - scattered from water  p - scattered/reflected from particles suspended in water  r - surface reflection

23.  p - total scattering from the water column is dependent on 1. b ( ) - water scattering coefficient 2. SM ( ) - Suspended inorganic minerals 3. DOM ( ) - Dissolved organic material 4. Chl ( ) - Chlorophyll within the column Wavelength dependent!

24.  T - total absorption from the water column is dependent on 1.  ( ) - water absorption coefficient 2. SM ( ) - Suspended inorganic minerals 3. DOM ( ) - Dissolved organic material 4. Chl ( ) - Chlorophyll within the column Wavelength dependent!

25. 12-8 in Jensen Water reflectance as a function of sediment concentration

26. Chlorophytes Euglenophytes Glaucophytes Haptophytes Pyrrophytes (dinoflagellates) Bacillariophytes

27. Reflectance vs. phytoplankton density

28. Figure 12.9 Jensen Effects of phytoplankton on water surface reflectance @ different sediment concentrations Without sediment present

29. Effects of bottom reflectance In clear, shallow (< ~30 m) water, the reflectance properties of the bottom influences the total flux off of the water surface Therefore, in clear shallow water, variations in total flux are related to the composition of the bottom itself

31. Sources of variation in bottom reflectance Variations in mineral content of soil (sediment), gravel, rocks on bottom Presence of coral Presence of sea grass

32. Simple model of flux off of a water surface ii  r - surface reflection Surface reflection has three components 1.Direct specular reflection of sunlight 2.Specular reflection of indirect, scattered light 3.Sunglint

33. Sunglint occurs when the sensor and the reflected sunlight having the same angle Wind results in small waves (capillary waves) on any water surface. These waves results in facets that result in direct specular reflection of a certain portion of sunlight. Specular reflection off of a smooth ocean = artificially high signal at sensor. Specular reflection off of a rough surface = artificially low signal at sensor.

34. Sunglint “Sunglint is a phenomenon that occurs when the sun reflects off the surface of the ocean at the same angle that a satellite sensor is viewing the surface. “In the affected area of the image, smooth ocean water becomes a silvery mirror, while rougher surface waters appear dark.” Source: Wikipedia – generally not to be trusted but good for sunglint!

35. Water Summary In summary, total radiance from a water surface,  t-w is comprised of 1. Radiance from surface reflection 2. Radiance from water scattering 3. Radiance from reflection/scattering from particles/phytoplankton suspended in the water column 4. Radiance from reflection of EM energy from the bottom of the water body

37. Clouds Do not reflect Solar radiation well in all directions Need multiple observations from different points Thermal properties are important

38. Albedo a measure of reflectivity of a surface or a body a ratio of EM radiation reflected to the amount incident upon it Reflectance of an object aggregated over a broader segment of the EM spectrum (0.3-2.4 microns) in all directions Expressed in 0-100% Clouds: varies from 10-90%, depending on drop sizes, liquid water or ice content, thickness of a cloud, and the solar zenith angle.

39. Clouds Information and imagery from http://earthobservatory.nasa.gov/Library/Clouds

40. High Clouds Information and imagery from http://earthobservatory.nasa.gov/Library/Clouds High clouds increase greenhouse effect and subsequently increase surface temperature

41. Middle and Low Clouds Information and imagery from http://earthobservatory.nasa.gov/Library/Clouds Low clouds decrease greenhouse effect and subsequently decrease surface temperature

42. Deep Convective Clouds Information and imagery from http://earthobservatory.nasa.gov/Library/Clouds Deep convective clouds do not influence greenhouse effect and are neutral to surface temperature

43. Precipitation Hurricane Bonnie precipitation from TRMM data

44. Snow and Ice Climate change observations Hazards (avalanches etc.) Sea ice extent Fresh water supply

45. Clouds and Ice: spectral response Very similar in visible and NIR wavelengths Very different in wavelengths over 1.5µm - snow and ice strongly absorb the energy - clouds strongly reflect the energy Source: http://www.cps-amu.org/sf/notes/m1r-1-8.htm

47. Soil composition Several layers contributing to energy flux off of soils: litter Organic matter content minerals iron compounds bedrock http://www.physicalgeography.net/fundamentals/images/soil_breakdown.gif http://cals.arizona.edu/pubs/garden/mg/soils/images/p3large.gif

48. Energy-Target Interactions General Rule: I = R+A+T Where R – reflected radiation; A – absorbed radiation; T – transmitted radiation For Soils: I = R+A T is near 0

49. General Spectral Characteristics Dry soil: increase in reflectance with increase in wavelength in visible and NIR portion of the spectrum The differences in reflectance of various soils are relatively consistent throughout various wave length regions.

50. Soil properties influencing its spectral characteristics texture organic matter iron oxide

51. Texture Texture – relative proportion of clay ( <0.002mm ), silt ( 0.002 – 0.05 mm) and sand ( 0.05 – 2 mm ) particles present in a mass of soil. Texture moisture content surface roughness

52. Texture: particle size http://images.google.com/imgres?imgurl=http://dbs.umt.edu/sci226/gifs/images/lab_soils/img3_small.gi f&imgrefurl=http://dbs.umt.edu/sci226/lab8_soils.h tm&h=270&w=359&sz=17&tbnid=r6PqflSXM5gJ:&t bnh=87&tbnw=117&hl=en&start=3&prev=/images %3Fq%3Dsoil%2Brelative%2Bparticle%2Bsize%2B soil%26hl%3Den%26lr%3D%26sa%3DG http://www.geog.plym.ac.uk/labskills/Images/triangle.gif

53. Texture: moisture content sandy soil silt soil Soil texture determines the ability of soil to contain large amounts of water. Clay particles have strong hydroxyl absorption at 1.4 and 2.2 micrometers The finer the soil texture, the greater the soil’s ability to maintain a high moisture content in the presence of precipitation. The greater the soil moisture, the more incident radiant energy absorbed, the less reflected energy. clay soil

54. Texture: moisture content With the increase in moisture content, reflectance decreases, particularly in water- absorption bands (1.4, 1.9, 2.66, 2.73, and 6.27 micrometers) The decrease in reflectance is NOT directly proportionate to the increase in moisture content

55. Global distribution of soils water holding capacity http://soils.usda.gov/use/worldsoils/mapindex/whc.jpg LOW MODERATE HIGH

56. Organic matter http://images.google.com/imgres?imgurl=http://www.na.fs.fed.us/spfo/pubs/n_resource/wetlands/images/p21pic3.jpg&imgrefurl=http://www.na.fs.fed. us/spfo/pubs/n_resource/wetlands/wetlands5_soils.htm&h=331&w=183&sz=46&tbnid=_zGkFvH9AMMJ:&tbnh=114&tbnw=63&hl=en&start=4&prev=/i mages%3Fq%3Dorganic%2Bsoils%26hl%3Den%26lr%3D

57. Organic matter Amount of organic matter (more matter – lower reflectance) Degree of decomposition (more decomposed – lower reflectance)

58. Iron Oxide http://images.google.com/imgres?imgurl=http://www.na.fs.fed.us/spfo/pubs/n_resource/wetlands/images/p21pic3.jpg&imgrefurl=http://www.n a.fs.fed.us/spfo/pubs/n_resource/wetlands/wetlands5_soils.htm&h=331&w=183&sz=46&tbnid=_zGkFvH9AMMJ:&tbnh=114&tbnw=63&hl=en& start=4&prev=/images%3Fq%3Dorganic%2Bsoils%26hl%3Den%26lr%3D

59. Iron Oxide Increase in iron oxide causes decrease in reflectance in the visible spectrum but does not significantly affect wavelengths over 1.1 micrometers

60. Texture: surface roughness IN THEORY, with a decrease in particle size, surface becomes smoother and more reflective. This assumes that the soils contain no moisture, organic content, or iron oxides. So, a perfectly dry, clayey soil = higher reflectance But... We know clay holds water, which decreases overall reflectance, particularly in the mid-IR The relationship between the amount of silt particles and surface reflectance is almost directly proportional.

61. Soils Summary All other things held constant... Reflectance decreases with an increase in moisture content. Reflectance increases with a decrease in particle size. Reflectance increases with a decrease in surface roughness. Reflectance decreases with an increase in organic matter content. Reflectance decreases with an increase in iron dioxide content.

62. Caveats Soil is a very complex mixture of materials which affect its absorptance and reflectance characteristics. Soil characteristics are closely interrelated which significantly affects reflectance characteristics.

63. Geomorphology applications of Remote Sensing Geological features and landforms Coastal landforms and processes Desertification Glacial landforms and processes Fluvial landforms and processes Natural hazards Soil erosion Information and imagery from NASA Remote Sensing tutorial (section 17) http://rst.gsfc.nasa.gov Go through the next few slides on your own

64. Fluvial landforms (1): stream flow Landsat imagery of river network in South Yemen Radar imagery of river network Meandering Mississippi

65. Fluvial landforms (2): river deltas Mississippi delta Arabian sea delta

66. Fluvial landforms (3): other Niagara Falls Great Lakes

67. Glaciers Icecap in southern Iceland Alaskan Alpine glaciers Gulf of Alaska: Combination of Landsat and DEM

68. Glaciers: movement

69. Volcanoes and craters

70. Eolian Refers to the activity of the winds, and their ability to shape the Earth’s surface.

71. Coastal Fjords Outer banks NC Atoll

73. Land cover vs. Land use Water bodies Coniferous forests Deciduous forests Grasslands Parks Pasture Logging concession Croplands Urban areas (commercial & residential) Aquacultures

74. Challenges Urban landscapes are very diverse in terms of materials present on the ground This leads to mixed pixels, even at Landsat’s spatial resolution. Usually has relatively small objects of interest – requires high and very high resolution High = 30 meters Very high = <1-10 meters Urban areas have specific seasonality They will look different in fall vs. winter due to vegetation change (wavelength dependent).

75. 1 x 1 m 20 x 20 m (SPOT)30 x 30 m (Landsat TM) 4 x 4 m10 x 10 m (SPOT)

76. The same area is represented in different ways

77. How to Identify Urban Features Shape! Texture! Best detected in visible and NIR (thus cyan cities in your lab exercises) Helpful information from thermal IR

78. Stages of Development

79. 1995 1975

80. 1974 1,040 urban hectares 1994 3,263 urban hectares 315% increase