Monday, 29 October 2007

It's the monsoon season in Thailand!

I have just read the latest postings on Mark's web diary.....
'rain this morning and for most of the day'
'torrential monsoon rain all afternoon - rain like Mark has never experienced before' .
Cue some chat about tropical rain, I think!

Firstly, tropical rain tends to be much more intense than the rain we experience in temperate latitudes. The main reason is that it is related to convection activity associated with heating of the earth's surface. Secondly, although there is rain at all seasons, there is generally one part of the year (known as the wet season) when rainfall amounts are much more than during the rest of the year. The climate data for Songkhla in the south of Thailand illustrates the pattern well...
The abrupt change in total precipitation from month to month is another common feature of tropical climates. While temperatures only vary by a degree of two throughout the year, rainfall amounts vary enormously. Here, for example, in the south of Thailand, the rainfall in January is one fifth of the December total. The reason is related to shifting wind belts which can very swiftly swing from one direction to another bringing warm, moisture laden air from surrounding seas and oceans for part of the year and carrying it away for the remainder.

Unfortunately, Thailand is right in the middle of the wet season just now and if anything, it looks like it is about to get wetter! However, with luck, Mark should be in Australia by the time the worst of the rains hit Thailand.

In common with many Tropical countries, the annual rainfall regime dictates the annual agricultural cycle in Thailand. Although there is some irrigation fed cultivation, most of the farming is rain-fed wet season rice cultivation. Fields are prepared in August, planted in October and the rice is harvested in February. The fields then lie empty awaiting the arrival of the next rainy season. The image below shows rice fields in the dry season just to the south east of where Mark was cycling today (in one of the rare areas of high res coverage in Thailand)...

And here is an idea of what that rain Mark describes might be like (filmed in Penang, Malaysia)..

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