Food & Climate 

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Worksheet: Drought in the Mediterranean

Sheet 2: Drought driving factors

In the text “Drought in the Mediterranean” you have read about the NVDI.

Two Explanations of NVDI are:

a) Normalized Difference Vegetation Index (NDVI) imagery is calculated from the red and near infra-red reflectance observed by the AVHRR (Advanced Very High Resolution Radiometer) sensor on NOAA meteorological satellites.

The NDVI image provides an indication of the vigour and density of vegetation at the surface. Images of NDVI are sometimes referred to as "greenness maps" since they represent the vegetative vigour of plants.

The time series of NDVI data (from 1982 to the present) allows analysis of changes in vegetation vigour and density in response to bio-physical conditions (including plant type, weather and soil).
Processed by NASA and the U.S. Geological Survey, the data are represented as pixels (cells), with each pixel representing an area of 8.0 x 8.0 km.
NDVI values range between -1 and +1, with dense vegetation having higher values (e.g., 0.4 - 0.7), and lightly vegetated regions having lower values (e.g., 0.1 - 0.2).

The primary use of these images is to compare the current state of vegetation with previous time periods, for example the same time in an average year or a reference year (a particularly good or bad year) to detect anomalous conditions.

b) To measure and map the density of green vegetation across the Earth's landscapes, scientists use satellite sensors that observe the distinct wave lengths of visible and near-infrared sunlight that is absorbed and reflected by the plants.

Calculating the ratio of the visible and near-infrared light reflected back up to the sensor yields a number from minus one (-1) to plus one (+1).

The result of this calculation is called the Normalized Difference Vegetation Index, or NDVI.

An NDVI value of zero means no green vegetation and close to +1 (0.8 - 0.9) indicates the highest possible density of green leaves.

(Source: http://earthobservatory.nasa.gov/Observatory/Datasets/ndvi.fasir.html)

Exercise 1: 

The following satellite pictures show the NVDI (Normalized Deviation Vegetation Index) of the year 1998 for Spain.
Look at the simulation and describe the changes throughout the year!

Please click for a higher resolution into the picture! (330 K)
Quicklook of the Iberian Peninsula in 1998, Source of the animation: http://satgeo.zum.de/satgeo/beispiele/interpretation/ndviueb.htm

Exercise 2:

There is a struggle for water in dry countries.
Imagine different stakeholders and look for their arguments to get the greatest portion of the water.

  
Exercise 3:

In the following table the temperature and precipitation data for a place in Spain is shown.
Use the table and create a climate diagram.

Find out where in Spain this climate station could be.

Exercise 4:

Is this typical for Mediterranean climate?
Give reasons for your opinion.

Exercise 5:

Look at the following climate diagrams!
(Be careful to note the order of months.)

Which ones are of the Mediterranean type?
Where could the other station be situated?

Exercise 6:

Have a look into your atlas.
Where else can you find Mediterranean climate?
Have these regions something in common?
Can you explain this fact? 

Exercise 7:

You have learnt about the water use in Spain and Norway and the relations between water resources and water use in those two countries.
What about your country?

First have a guess how the situation is there, then look at the website
http://www.fao.org/ag/agl/aglw/aquastat/dbase/index2.jsp

Transform the data for water use into a circle diagram and compare  the water use and the water resources of your country to the situation of Spain.
Is there also a risk of drought in your country?

About this page:

- Author: S. Schnell - University of Nürnberg - Germany
- scientific reviewing:
- educational reviewing: Dr. Schrettenbrunner / J. Heres
- last update: 07.01.04