Thursday, September 16, 2010
Will it Ever Stop Raining?
It's raining again! It seems like it's been raining everyday here in Jogja, and that makes it very humid here. It rains a lot because this is a tropical location (like Honolulu) and an island. However, under normal circumstances there is a dry season and a wet season, again much like Honolulu. Think of your experiences. When does it usually rain in Honolulu? When is it generally dry? The pattern matches this area of Indonesia as well. Climatologists (people that study long-term weather and atmospheric trends) refer to this dry-wet season pattern as a monsoon. Many people think that monsoon means "lots of rain", but this isn't exactly true. Monsoon refers to a seasonal shift in winds. This means that during one season the prevailing wind blows from one direction, whereas during the other season the wind blows from a different direction. Probably the most well known example of a monsoon pattern is India. You may have seen stories on the news or in National Geographic about the monsoons there. In India for part of the year the wind comes from the north, which is all land and mountains, so there isn't much rain. However during the other part of the year the wind brings air from the Indian Ocean and Bay of Bengal (find these on a map), and so the air is very moist and thus there is rain.
The monsoon is important for farmers but it has also been important historically for global trade! Find Indonesia on a map. Now locate India and China. You can see that Indonesia is about in the middle of the sea route between these two nations, which are home to ancient civilizations. Hundreds of years ago, before steam and diesel engines sailing was the best way to go long distances, especially with heavy cargo. The interesting thing about Indonesia is that the monsoon winds actually aided trade. For part of the year the winds blow towards Indonesia, making it easy to go from China or India to Indonesia. Then for the other part of the year the winds blow away from Indonesia, making it easy for Chinese and Indian traders to get home!
These islands in the past have been referred to as the "Spice Islands". That's because this is the natural home of many spices like black pepper, nutmeg, cloves, and many others! You are probably very familiar with some of these, but just a few hundred years ago in Europe these spices were virtually unknown. When they were discovered by Europeans a huge demand was created. Can you imagine eating food without pepper or other spices? The demand for spices from what is now known as Indonesia was so great that these spices for a time were worth more than gold! Monsoon winds helped stimulate the trade between Indonesia and Europe.
The problem these days though is that the monsoon seems to be getting less reliable. Indonesia is an agricultural country, and rice is the major crop. It is very productive, especially in the tropics. However, it needs regular and plentiful water for maximum yields. The other day I was talking to a farmer (in Indonesia), and he told me that global climate change (sometimes referred to as "global warming") seems to be disrupting the monsoon. When it rains unexpectedly the crops are damaged, and the farmers get confused as to when to plant new rice. Now back to my first point...the rain... Remember I said that Indonesia (like Hawaii) has a dry season and a wet season. The problem is that now it's supposed to be the dry season! So it's not just me that's asking this question...the farmers are too.
I'll write more soon, but in the meantime you might want to try to answer some of the questions I've included below.
Can you find a climate map that shows where monsoon climates are found? Try using the internet. Can you find some stories about the relationship between global climate change and shifting monsoon seasons?
What do I mean when I use the term "tropics"?