Friday, March 6, 2009
Last Night's Rain
Hello 02. Today in class, Mr Heah posed a very thought-provoking and intriguing question - where did last night's torrential rains come from? We discussed the answer in class, and it is as follows.
The rain was essentially monsoonal rains, coming from the South China Sea.
Since the thermal equator was at the Tropic of Capricorn just last december 21st (Winter Solstice), the Southern Hemisphere, as compared to the Northern Hemisphere, has been receiving more intense heat these past months from December till today in March. As such, the surface air of the Southern Hemisphere is warmer, expands more, and the Southern Hemisphere hence has a lower air pressure. Thus the colder, denser air of the Northern Hemisphere is moving southwards, and going by the direction of wind flow as shown in the Hadley cell, the air will flow in the south-west direction. Thus, as the wind travels over the South China Sea, it picks up moisture, and when the moisture-laden rain passes Singapore, it results in monsoonal rains occuring in Singapore last night!
andrew