Shanghai, China
|  | Shanghai natural colour | |
From an astronaut's point of view
The MERIS instrument onboard Envisat provides us with a partial view of the central Chinese coast and the East China Sea. The image is processed to simulate natural colours. In order to obtain bright colours, as we are used to seeing, the image has been contrast enhanced. Astronauts from their spacecraft would never see the area in such bright colours, but just in a brownish colour tone.
Click on the image above to get a larger version of the natural colour image of Shanghai.
In the centre of the image you can see the Yangtze River. The city of Shanghai is situated south of the river, but we cannot see it in the image because it is covered by clouds. South of Shanghai is the hilly forest of the Zhejiang Province. Slopes which are not illuminated by the Sun appear very dark. The region in the northern part of the image belongs to the Jiansu Province. Even though it is a rural area, mist and smoke still pollute its atmosphere. The smoke partially originates from the region's industries.
Compare the Envisat image with the best map you can find in your school atlas.
Try to locate Shanghai.
| | | Shanghai - NO2 concentration |
Air pollution
Envisat studies atmospheric pollution. The satellite provides us with daily information about the atmosphere. China is one of the problematic regions of the world. Let's access this data source.
Go to the Tropospheric Emission Monitoring website
and look for Tropospheric NO2.
Ozone, nitrogen and sulphur dioxides are carefully monitored by Envisat at a global and regional level. The information is even provided in 'near real-time' for ozone.
'Near real-time' means that the delay between image acquisition by the satellite and its reception by a user, for instance, is relatively short. This delay corresponds to the time needed for data processing and its communication from one location to the other.
Take a look to the monthly averages in 2003, especially for NO2 over China, and compare them with other highly industrialised regions of the world.
List the regions mostly affected, and note the maximum values measured each month!
Try to rank the regions according to your results.
| | Shanghai total suspension | |
Yangtze River sediments
Download here a larger version of the Shanghai total suspension image(0.6 Mb)
The MERIS sensor onboard Envisat tells us a lot about the oceans. The 15 spectral bands can also be modelled to estimate the amount of small particles floating in the water. These small particles consist eroded soil, and other fine sedimentary material, which make the water look dirty. The waters of river inlets are therefore often brown or yellow. In order to show the quantities involved, we have artificially coloured the image.
Here is the coding:
| Colour |
Material in suspension in the water
(g/m3) |
| Yellow |
>72 |
| Yellow reddish |
72 - 30 |
| Red |
30 - 5 |
| Brown |
5 - 3 |
| Green |
3 - 1,9 |
| Light blue |
1,9 - 0,03 |
| Blue |
<0,03 |
| Black |
Land or clouds |
Open the image in LEOWorks. Remember that the pixel size is 300 m.
Observe the huge plume of earthy material that is flushed into the sea.
How far out does this plume reach?
Measure the distance from the river mouth for the maximum measurable quantities!
Can you imagine that even out there, the water is still yellow?
How many kilometres into the sea is it?
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