1. List at least three geophysical parameters useful in monitoring Fresh Water availability over land.
ANSWER:
Precipitation
Evaporation & Evapotranspiration
Soil moisture
Precipitation provides the quantum of source water available in various forms in the earth’ surface - form of lakes, stream flow etc… This geophysical parameter provides the SOURCE & QUANTIFICATION of fresh water available and form the basis of water resource management. Evaporation & E. transpiration is the quantification of direct loss of the above fresh water resource. The available fresh water would thus be taken as the amount of fresh water available minus the loss due to the above factor. Soil moisture provides the quantification and qualification of the geology of the surface, it’ s capacity to retain water and its capacity that can be utilized for artificial recharge of the fresh water that falls on it. For example, clay would not allow percolation; extremely dry soil condition (that prevails over very hot areas) will not allow retention of rain water as it will be “completely baked” (this typically happens when the rain fall starts after a dry spell). Thus, soil moisture is one of the parameters that provides information on “retainability” and “ re-charge potential” of the fresh water over a parcel of land.
List two advantages of using remote sensing data over in situ, surface station data.
ANSWER:
Provides information where there are no ground-based measurements, including over oceans
Provides globally consistent observations
NOTES ON THE ANSWER:
Remote sensing methods provide a LARGE SCALE PERSPECTIVE on water resource management, natural calamities and macro climatic environmental deviations..
All the water cycle components can be measured / calculated using Remote Sensing methods, which would not be possible in ground level studies. This aspect is very important while estimating, quantifying, planning, evaluating and re-assessing the water resource management of any scale – from a parcel of land to a continent.
3. Name different types of satellite orbits.
ANSWER:
Geostationary orbit (GEO) or Geo Synchronous
Low Earth Orbit (LEO)
Polar Orbit
NOTES ON THE ANSWER:
As the name implies, a “GEO” appears ‘fixed’ in space. The satellite is put into orbit about 36000 kms above the earth’s surface and its rotation period is the same as earth’s i.e. its orbital period is about 24 hours. In effect, it follows the “patterns” of the various geophysical parameter dynamics as the earth’s surface. GEO or Geo Synchronous orbit (GSO) are used interchangeably, though there is a subtle difference between the two orbits. A Geo Synchronous orbit “returns” to a particular point in a particular time for an observer in earth. A GEO on the other hands appears always “fixed” at one particular point for an observer in earth. The factor of “time” as a dimension is removed in case of a GEO for an observer in the earth. Communication satellites use the GEO or very near GEO orbits.
Low Earth Orbits (LEO) satellites move at a lower level i.e. at about 160 – 2000 kms. The movement is “relative” to the earth and can move either in polar or non polar orbit. LEO is an orbit around Earth between the atmosphere and below the inner Van Allen radiation belt. A low earth orbit is simplest and most cost effective for a satellite placement and provides high bandwidth and low communication latency.. Earth observation satellites and spy satellites use LEO .The International Space Station is in a LEO about 400 km (250 mi) above the Earth's surface.
A polar orbit is an orbit in which a satellite passes above or nearly above both poles of the earth. It therefore has an inclination of (or very close to) 90 degrees to the equator. The disadvantage of polar orbit is its inability to apply remote sensing to one fixed spot in the earth. Polar orbits are applied for earth mapping, reconnaissance and for some weather satellites. The telecommunications mode also uses polar orbit. Orbits with a high inclination angle to equator, are usually called polar orbits
4. What type of orbit do the following satellites have?
ANSWER:
TRMM - Non polar orbiting satellite
Aqua - Polar orbiting “ascending” day time orbit satellite
5. State at least two strengths of atmospheric model data.
ANSWER:
Modeling provides the juxtaposition of remote sensing and in situ observations of the geo physical variables and including those which cannot be measured by in-situ methods.
Provides additional variables which cannot be observed directly – 3 D humidity in atmosphere, near live time rainfall / extreme rainfall data The core CAPABILITIES of atmospheric model data are:
Ability to provide high accurate data of the geo physical variables which go into the planning and prediction of water resource management and water cycle
Ability to provide high accurate data for understanding climate change and environmental process and “incident” measurements, monitoring regional wet / dry periods, extreme climatic events like extreme rainfall, mapping flood and land slide potential and also used for agriculture monitoring
6. What is the spatial coverage of a geostationary satellite?
ANSWER:
Spatial coverage of GOES is “GLOBAL”; 60deg N and 60 deg
Spatial resolution is “Ground coverage per pixel”. It refers to the amount of area observed by the sensor. The spatial resolution of GOES is 1km visible, 4km infrared.
7. What is a passive remote sensor? Which one of the following is not a passive sensor?
ANSWER:
a. PR
b. TMI
c. MODIS
Passive remote sensors measure radiant energy reflected or emitted by the earth-atmosphere System Radiant energy is converted to geophysical quantities.
PR is not a passive sensor.
8. What is TRMM satellite’s spatial coverage?
ANSWER:
Latitude: 50°S - 50°N; Longitude:180°W - 180°E Global
9. MODIS is flying on :
ANSWER:
a.TRMM
b.Terra
c. Aqua
d. Landsat
10. What is one limitation of MODIS that results in missing/un-available snow observations?
ANSWER:
No Snow Mapping Under Clouds
11. Which of the following parameters are not directly derived from satellites but are derived from models?
ANSWER:
Rain Rate
Run off
Snow Fraction
B: Run off
Run off and stream flow is calculated with land atmosphere and hydrology models. These models utilize satellite observations as inputs.
12. Which satellite data requires more processing? Level-1 or Level-3?
ANSWER:
Level 3 needs more processing.
Level 1 products provide “orbital data” . They need more user control and are harder to use. They, however, provide HIGH spatial / temporal resolution.
Level 3 products need more processing. They are easier to use and have lesser user control. The products map the geo physical variables on a uniform space – time grid and the data can be made available in multiple resolutions.
They provide lower spatial / temporal resolution as compared with Level 1 products. However, these resolutions are in space – time grid format
13. Which of the following sensors has larger swath size? a: PR b: TMI
ANSWER:
T M I
Precipitation Radar (PR) is an ACTIVE rain sensor
TRMM Microwave Imager (TMI) is a PASSIVE sensor
Swath of PR = 220 kms
Swath of TMI = 760 kms ; higher temporal resolution
14. What is the temporal resolution of TMPA data?
ANSWER:
Daily, once in 3 hours..
TMPA : TRMM Multi-satellite Precipitation Analysis
The product name is 3B42.
This product combines passive and active sensor rain rates, and used in hydrology and decision support models.
The temporal resolution of TMPA TRMM 3B42 is daily, once in 3 hours.
15. Does MODIS provide measurements over Arctic region?
ANSWER:
YES.
16. List two web-sites where MODIS Standard Product is available.
ANSWER:
MODIS Snow product are available from the National Snow and Ice date centre http://nsidc.org/
Selected Aqua – MODIS snow product from Reverb/ECHO @ http://reverb.echo.nasa.gov/reverb
Near – real time and standard MODIS products from http://land-modis.eosdis.nasa.gov/
17. Which parameters are available in MODSCAG?
ANSWER:
Fractional Snow Cover
Grain Size
Albedo of that snow from surface reflectance data
18. Which hydrology model and TRMM data product is used by SERVIR?
ANSWER:
TRMM 3B42RT: Near-Real Time
19. Which parameters are monitored by SERVIR over Africa?
ANSWER:
A SERVIR-Africa project on biodiversity mapping and the vulnerability of biodiversity to climate change in East Africa
20. Go to http://flood.umd.edu and list the parameters shown in the three maps that appear on the main page.
ANSWER:
Flood detection/ Intensity { depth above threshold (mm) }
Stream flow 12km res. (m3/s)
Rainfall (mm)
21. What are the units of : Rain rate; Snow cover ; stream flow
ANSWER:
a. Rain Rate - millimeter / unit area / unit time
Rain fall rates are generally reported as centimeters per hour.
b. Snow Cover -
SNOW COVER EXTENT : km2
SNOW COVER DEPTH : cm
SNOW WATER EQUIVALENT : mm
c. Streamflow - cubic meter / second
22. Which of the following parameters can impact run off?
Evapotranspiration; Soil Moisture ; Soil Type ; Snowmelt
ANSWER:
Soil moisture , soil type and snow melt
23. Do you agree with the following statements?
ANSWER:
There is no need of surface-based observations since there are remote sensing and model-based data available globally (Agree Disagree)
Disagree
Remote sensing measurements are more accurate than surface-based observations (Agree Disagree)
ANSWER:
Agree