a. cloud

Cloud is formed when air rises, cools and the water vapour (an invisible gas) turns into water droplets (a visible liquid). We can see this happening on a frosty morning when we breathe out warm air containing water vapour which quickly cools and turns into water droplets. (This looks like smoke coming from our mouths).

One way in which air is forced to rise, cool and produce cloud is when air moves from the sea and has to climb over the land e.g. :-

As this air is forced to climb even further we may get rain (relief rainfall). Usually the higher up we go, the wetter it is.
If we think about Ayrshire, on this diagram towns 1, 2 and 3 would be :-
1. Ayr 850 mm. average total rainfall
2. Kilmarnock 1000 mm. average total rainfall
3. Fenwick 1200 mm. average total rainfall
We can often find it dry at Ayr, drizzle at Kilmarnock and rain at Fenwick.

We measure the amount of cloud cover by looking at the sky and seeing how much of it is covered by cloud. This cloud cover is measured in OKTAS (eighths of the sky covered in cloud) eg :- 0 OKTAS = No Cloud
4 OKTAS = Half the sky (4/8) covered in Cloud.

The two main types of cloud we get are :-

b. stratus ... a total layer of cloud covering the whole sky

 

b. sunshine

The amount of sunshine during the day is measured on a sunshine recorder.

The glass ball focuses the sun's rays onto the special card behind it. The rays burn the card so that the times when the sun was shining can be read from this card. We can thus calculate the total hours of sunshine each day.
We measure sunshine in hours.

Every day a new card is fitted onto the Sunshine recorder.

 

This card shows burn marks on it. The card also shows time on it so we can tell when the sun started to shine, for how long it shone and when it stopped shining.

On this card the sun
:- started shining at 0600 hrs (6 AM)
stopped shining at 1000 hrs (10 AM)
and shone for 4 hours
started shining again at .............

 

Cloud Cover + Sunshine Questions

C. + S. 1. Fill in your weather Summary Sheet for sunshine.

C. + S. 2. For cards 1 and 2 give a detailed description of :-
the times when the sun started to shine
the times when the sun stopped shining and
the total hours of sunshine for each day.

C. + S. 3. Use graph 2 in your worksheet to draw a sunshine card showing the sun :-
started to shine at 0700 hrs. (7 am)
stopped shining at 0900 hrs (9 am)
started to shine at 1030 hrs. (10.30 am)
stopped shining at 1300 hrs (1 pm)
started to shine at 1430 hrs. (2.30 pm)
stopped shining at 1700 hrs (5 pm)

C. + S. 4. For how many hours did the sun shine that day ?

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