Normalised Difference Vegetation Index (NDVI): Vegetation From Space

Exercise 1.
1.         Describe the NDVI images

In simple words, NDVI stands for normalized different vegetation index. How NDVI works is that through Near-Infrared Radiation reflectance aka NIR reflectance. Different value of NIR reflectance indicates different vegetation on the earth surface. For example, high NIR reflectance normally indicates area with high vegetation and vice versa.

From the formula, (NIR- visible red)/ (NIR + visible red). If the value shown close to 1, normally that area were high in vegetation. This happens to be the other way round when the value is close to -1. What else can we know from the range -1 to 1 is that the status of the crop. For example, the health of the crops.

From the exercise, dark green shows healthy crop, with light green show unhealthy crops while white color shows residential area. By comparing the 2 images, SPOT NDVI January 2000 and SPOT NDVI August 2000, significant changes is portion of darker green color increases which indicates more healthier crops can be found in later.

2.         Where do you find the most abundant vegetation

Peru

3.         Where do you find the least abundant of vegetation?

            Argentina

4.         Compare the precipitation maps for two seasons and try to explain the changes in vegetation from January to August.

            Vegetation of an area in basically depend on sufficiency of water or precipitation to undergo normal processes like photosynthesis and so on. From what we know, precipitation is normally affected by wind direction. During December to February wind flown from North-East towards the central of Latin America, winds carries cloud and caused more precipitation over there. As for June to August, wind flows from South- East to the north part of the Latin America, so it just has more precipitation on north part. Therefore the patterns is in central part of the Latin America, from Dec to Feb has more precipitation but dry season from June to Aug. In north part of Latin America, June to August has more precipitation but less from Dec to Feb.

5.         Find some area where there is much variation in the NDVI. By comparing the NDVI with the precipitation map can you explain the variation?

            Brazil , Bolivia and Argentina as I mention before NDVI value reflects the healths of a plant. These area suffers from droughts at June to August and sufficient precipitation at Dec and Feb. Therefore, plant is healthier from December to February which has high NIR reflectance and NDVI is near 1. While plant is unhealthier from June to August which has high red reflectance and NDVI is near -1.

6.         Find some desert area. Can u explain why precipitation is so low in these area?

            For example, northern part of Chile. In these area, wind blows wildly and carries all the cloud away. That’s why low precipitation in these area.

7.         There are some area with high NDVI values in both seasons, Why?

            For example,Urugual and Chile. Because these area are not affected with wind flow.

Exercise 2

1.      1.                   Observe and describe the variation in the NDVI value in the year 2000

From the observation, when NDVI of an area increases, colour changed from light green into dark green. While NDVI decreases, colour changed from dark green into light green.

2.     2.                    In what months is the NDVI at its maximum in Amazon basin? Why?

November, this is because dark green area covered the most in Amazon

3.      3.                 Observe the Dec image for the northeastern part of Brazil along the Atlantic coast and inland. Can you explain the vegetation image?

During Dec, image shows higher in light green colour which mean is suffer from dry seasons due to wind blow from north-east to south.

4.     4.                     Can you explain the variation in vegetation along the Pacific coast?

In my opinion, this mainly due to monsoon season which abruptly interfere with amount of precipitation.

5.     5.                      Compare the information on  climate as described in the maps in a normal school atlas with the NDVI image. How are yearly changes of the location of the Inter-Tropical Convergence Zone (ITCZ) reflected in the NDVI images?

ITCZ area converge trade wind and raising air that encircle the equator of the earth. The rising air produces high cloudiness, frequent thunder storm and heavy rainfall. The ITCZ shift north and south with the Sun seasonally. It is responsible for the wet and dry seasons in the tropics. The tendency for convective storms in the tropics is short in duration, usually on a small scale but can produce intense rainfall. Greatest rainfall typically occurs when the midday Sun is overhead. On the equator this occurs twice a year in March and September, and consequently there are two wet and two dry seasons. Further away from the equator, the two rainy seasons merge into one, and the climate becomes more monsoonal, with one wet season and one dry season. In the Northern Hemisphere, the wet season occurs from May to July, in the Southern Hemisphere from November to February.