Global Ecology Unique Perspectives from Space Based Satellite Sensors Instruments

Satellite remote sensing instruments provide unique global observational perspectives on the state of the biospheres occupying the land surface, coastal zones, the oceans, and the snow/ice-covered mountains and

*The views expressed herein are those of the authors and do not reflect that of any agency or program.

polar caps. They also provide detailed global observations of both natural and anthropogenically induced changes in land surface, atmospheric and climatic drivers that often determine ecological health, sustainability, and dispersals or dislocations. Together with more specific in situ observations, space-based remote sensing of the global environment enables the investigation of the interplay between the different components of the Earth/climate system and the interaction between local and global processes. These data facilitate the construction of mathematical and empirical models

Figure 1 Plants on land and in the ocean (phytoplankton) contain chlorophyll, a green pigment used during photosynthesis. Using satellite sensors, we can measure chlorophyll concentrations on land as well as in oceans, lakes, and seas to indicate the distribution and abundance of vegetation. Since most animal life relies on vegetation for nutrition, directly or indirectly, scientists refer to these images as snapshots of Earth's biosphere. Source: David Herring, NASA. Data from SeaWiFS Project.

that strive to simulate and predict Earth system processes, especially those that can have impacts on global and regional environments and ecosystems. Time series of observations and advanced visualization tools enhance our understanding of global ecological processes, several examples of which are presented here (see Figure 1).

Satellite remote sensing of the Earth system may be viewed in a broad sense as 'eyes' in the sky looking down with a unique perspective defined by specific bands or channels in the electromagnetic spectrum. Depending on the particular instrument or sensor, they 'see' the Earth in the ultraviolet (UV), visible (VIS), infrared (IR), near-infrared (N-IR), and microwave (MW) wavelengths. These wavelengths include both the short-wave solar radiation bands and the long-wave bands in which the Earth emits radiation to space. The ability of a satellite with 'passive' instruments to detect an Earth surface feature depends on the spectral characteristics ofthe feature or object in question. Thus, different frequencies or wavelengths will capture different aspects ofthe atmosphere or the land surface or vegetation or coastal, marine, and ocean ecology.

Most satellites carry 'passive' sensors that collect the reflected, refracted, or emitted radiation from the Earth's atmosphere or surface. The types of Earth features that are captured by these different spectral bands are summarized in Table 1 (see Box 1). Some satellites carry 'active' instruments such as radar and lidar, which generate and transmit electromagnetic signals toward the Earth.

The reflected return signal or return echo carries information on the structure and composition of the atmosphere and the underlying land surface/vegetation, inland water bodies, and the vast expanses of the oceans. Currently, a number of natural hazards are routinely monitored from space. Examples include crops and droughts, dust, smoke and pollution, forest fires, floods, severe storms and hurricanes, and volcanoes. As a novel technology, a new generation of satellites also monitors the Earth's surface and subsurface geological and hydro-logical environments via nonphotonic measurements of the gravity anomaly field. The surface and subsurface hydrological environments can thus be monitored to provide information on the habitats that permit or limit ecosystem.

Accurate surface positioning information is now routinely obtained from the Global Positioning System (GPS) satellite constellation. Together with geographical information systems (GIS), sophisticated data-processing algorithms, and complex mathematical and empirical models, the global ecological environment and ecosystems are currently observed and analyzed to a historically unprecedented degree. A time history of remote sensing information provides crucial data on the dynamics of change in ecosystems as they respond, adapt to, and interact with the other components of the Sun-Earth system.

The space applications program of the United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOUS) identifies the following areas of applications that particularly benefit from remote sensing data

Table 1 EOS/TERRA-MODIS spectral bands and their key uses

Range reflected Range emitted

Table 1 EOS/TERRA-MODIS spectral bands and their key uses

1

620-670

Absolute land cover transformation, vegetation chlorophyll

2

841-876

Cloud amount, vegetation land cover transformation

3

459-479

Soil/vegetation differences

4

545-565

Green vegetation

5

1230-1250

Leaf/canopy differences

6

1628-1652

Snow/cloud differences

7

2105-2155

Cloud properties, land properties

8

405-420

Chlorophyll

9

438-448

Chlorophyll

10

483-493

Chlorophyll

11

526-536

Chlorophyll

12

546-556

Sediments

13h

662-672

Atmosphere, sediments

13l

662-672

Atmosphere, sediments

14h

673-683

Chlorophyll fluorescence

14l

673-683

Chlorophyll fluorescence

15

743-753

Aerosol properties

16

862-877

Aerosol properties, atmospheric properties

17

890-920

Atmospheric properties, cloud properties

18

931-941

Atmospheric properties, cloud properties

19

915-965

Atmospheric properties, cloud properties

20

3.660-3.840

Sea surface temperature

21

3.929-3.989

Forest fires and volcanoes

22

3.929-3.989

Cloud temperature, surface temperature

23

4.020-4.080

Cloud temperature, surface temperature

24

4.433-4.498

Cloud fraction, troposphere temperature

25

4.482-4.549

Cloud fraction, troposphere temperature

26

1360-1390

Cloud fraction (thin cirrus), troposphere temperature

27

6.535-6.895

Mid-troposphere humidity

28

7.175-7.475

Upper troposphere humidity

29

8.400-8.700

Surface temperature

30

9.580-9.880

Total ozone

31

10.780-11.280

Cloud temperature, forest fires and volcanoes, surface temp.

32

11.770-12.270

Cloud height, forest fires and volcanoes, surface temperature

33

13.185-13.485

Cloud fraction, cloud height

34

13.485-13.785

Cloud fraction, cloud height

35

13.785-14.085

Cloud fraction, cloud height

36

14.085-14.385

Cloud fraction, cloud height

products and monitoring (http://www.uncosa. unvien-

na.org/pdf/reports/IAM2006E.pdf):

• remote and difficult-to-access areas like dense forests, glaciated areas, deserts, and swamps;

• areas undergoing rapid environmental change, including loss or fragmentation of ecosystems and related loss of biodiversity;

• wide-ranging impacts of pollution, from depletion of the ozone layer to tracing oil spills, photochemical smog, and other environmental impacts;

• identification, monitoring, and preparation of measures to cope with natural threats, such as storms, floods, droughts, forest fires, volcanic eruptions, geological faults, and mass movement;

• identification and analysis of social and physical vulnerabilities;

• disaster management; and

• areas affected by complex emergencies, such as armed conflicts.

Programs and projects of the UN system of agencies covering water management, coastal area management, disaster management, climate change, agriculture, desertification, mountain ecosystems, biodiversity, forest management, and mining are described in http://www.uncosa.unvienna.org/ uncosa/en/wssd/index.html. The constellation of operational and research satellites that monitor the Earth system, coordinated by the World Meteorological Organization (WMO) with the various space agencies of nations worldwide, is summarized in http://www.wmo.int/pages/prog/ sat/GOSresearch.html; also see http://www.wmo.int/ pages/prog/sat/Satellites.html. In recent years, following several ministerial summits on Earth observations, an international group has been formed to coordinate global

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