Sea Breeze

The difference in temperature between land and sea surfaces produced by the same radiation intensity leads to a circulation system known as land and sea breeze. Both land and sea breezes are examples of strongly forced circulations which either modify the large scale winds, or, in the case of large scale calm conditions, cause winds to blow across shore lines of the ocean, lakes and large rivers. The Coriolis force usually turns the winds so that the direction is nearly parallel to the shore.

The sea breeze can be demonstrated by using two cans of 3" diameter, such as pet food cans, and 1" height filled with fine dry dark soil and the other with water placed inside an box. The soil should be sifted and should be as dark as possible to increase the absorbency of light. If only light soil is available, darken it by mixing soot, copier toner or charcoal powder into it.

The box should be constructed so that the top and front are transparent but the other walls are either painted flat black or lined with construction paper.

petrie dishes in boxPlace both cans in an aquarium or a box with transparent top and front as in the diagram. For better visibility of the smoke used in the experiment, the inside of the back and side panels should be painted flat-black or lined with black construction paper. Then fasten, with cement or tape, a sheet of glass or plastic to the top; a transparent plastic sheet is taped to the front, so that it can be removed for setting the two tin pans inside or taking them out. Cut a small hole in the front plastic just above the base to insert some smoke.

Place a 150 or 200 watt light bulb about 4" above the middle of the top, so that the same radiation is received by each of the pans. The bulb is turned on, and after 15 to 20 minutes very slowly blow some smoke through the hole in the front panel being careful not to create any eddies. The smoke should merely seep into the box. Watch the smoke drift and describe the motion.

Material: Two tin cans of 3" diameter

One box with top and front removed

Some flat-black point

Transparent plastic to cover front and top

Some dark, sifted soil; water

A smoke source

A 150 or 200 watt light bulb.