GeSMOGraphy! Jakarta's Smog Problem and the Temperature Inversion

Sitting here in the bubble waiting on papers to clear, I was at something of a loss as to what to write about. Then it hit me, like a ton of particulate matter suspended in the lower atmosphere: I’ll write about the dense layer of smog that perpetually blankets the Greater Jakarta Metropolitan area. I noticed a layer of low-lying clouds on the plane ride from Jogja to Jakarta last week extended out 20-30 minutes of flight time, which must be around 100 miles (on approach). I’m hesitant to say with certainty that this regional cover is smog rather than something natural, but it wouldn’t surprise me. The megacity of 20 million belches out so much pollution on a daily basis that it obviates the need for sunscreen on “clear” days.

To give you an idea of the amount of crud, I walked barefoot outside on my friend's 32nd-floor terrace here in the heart of Jakarta. I counted the steps required to get the bottom of my feet covered with urban grime (see photo to the right) which, due to the height of the terrace, can only have been deposited via settling. It took a mere 17 steps to accumulate the filth you see in the photo, and a full 3 minutes to scrub my feet clean.

What is smog, you ask? “Smog” is a combination of the words smoke and fog and refers to air pollution from cars, coal burning for electricity generation and other industrial sources. There are several different types of smog, but among the most common are photochemical (1) smog, which results from the reaction of some industrial pollutants and sunlight. There is also particulate smog, which consists of the dirt, soot, dust, and other crud that makes it into the air.

Smog is a fundamentally geographic phenomenon because it is trans-regional in effects and the severity of smog is influenced by a number of factors including topography, latitude, and atmospheric and oceanic circulation. Smog is also a factor of development and counter-intuitively can give us clues as to the prosperity of a city. A significant percentage of smog comes from cars, which are relatively expensive goods. As people make more money in the developing world, one of the first things they buy is a car or motorcycle. Thus more smog might suggest that more people are making the leap into car ownership. In addition, bigger cities produce more smog, and in places where rural-to-urban migration is significant the problem is compounded. Rural-urban migration is seen by development geographers as part of the process whereby countries become rich, and so smog is an unfortunate byproduct of this process.

But smog can gives us clues about the climatological characteristics of a region as well. In the US the place most known for smog is Los Angeles. While it’s true that Los Angeles is a sprawling city with millions of cars (2) traveling millions of miles, there are natural factors at work as well. When the air quality is at its worst in LA it signals the presence of an inversion layer. Normally in the lowest layer of the atmosphere (3) the air temperature decreases as your elevation increases. You’ve probably experienced this if you’ve ever been hiking in the mountains. Under normal circumstances warm air at the surface of the earth can rise up through the atmosphere, where it cools down and is blown out by upper level winds. If there is pollution it will be carried away. However, when a temperature inversion is present it means there is a layer of warmer air higher in the atmosphere. Cool air won’t rise through warmer air, and so the inversion layer acts as a lid on the cooler, and in the case of LA, dirtier air below. Since the air can’t circulate, it accumulates smog (4). At night the air cools thus breaking the inversion layer barrier and allowing the pollutants to dissipate.

Landforms also contribute to smog problems. Another city known for its smog, Mexico City, also periodically experiences an inversion layer. However, Mexico City is in a valley (5) surrounded by high mountains (see the satellite image to the left). The mountains trap the polluted air. The problem is much worse in Mexico City than Los Angeles because there are so many more people and the government has been less able to implement measures to alleviate the problem.

Jakarta's smog is mainly produced by automobiles (70%) and is exacerbated by a temperature inversion and relatively light winds attributable to its location close to the equator. The air doesn't really circulate much here, and so the pollution tends to accumulate. Being close to the equator also ensures that there is a lot of sunlight year-round, which fuels the chemical reactions that lead to photochemical smog.

As yet another demonstration of how much crud there is in the atmosphere, I set up a little experiment. Out on the aforementioned terrace I scrubbed two of the "white" floor tiles as clean as I could get them. You can see the tiles to the right. The letters I taped on the tiles stand for "control" (C) and "experimental" (E). While I'm here in Jakarta I'll check the tiles on a daily basis. I'll clean the control tile daily to serve as a contrast; the experimental tile will be left to accumulate grime. We'll see if there is a noticeable accumulation after a couple of days.

In Hawaii we sometimes experience air pollution as well, but ours is a result of the volcanoes on the Big Island. You’ve probably noticed that on some days this “vog” (volcanic fog) is worse than other days. This is due to geographic factors as well. As you probably know, most of the time the weather in Hawaii is pretty breezy. This is caused by the trade winds, part of the global atmospheric circulation described in a previous post. The trade winds blow the vog away, but when the trades die down the air tends to become stagnant. This is a more frequent occurrence in the winter months. These are the days when it's most humid and hazy outside.

(1) The prefix photo means "light". Can you think of some other "photo" words? What do they have to do with light?

(2) I read once that one-quarter of the surface area of Los Angeles is covered with cars.

(3) The troposphere….I’ll write a future post about the vertical layers of the atmosphere when I can figure out a way to relate it to Indonesia. But for now you can see for yourself in the diagrams below. I took these from Texas A&M's Oceanworld site. The first graph shows the decreasing temperature with elevation in three US cities. Temperature is on the x-axis; elevation is on the y-axis. As you can see, the temperature decreases as you go higher in the troposphere. The second graph is a close-up of the first. Notice on the Dallas and San Diego plots that temperature actually increases with altitude. This is an inversion layer.



The inversion layer in San Diego is caused by an upwelling of cool water in the ocean near the city. The cool water in turn cools the air closest to the ground.

(4) Hawai'i frequently experiences an inversion layer as well. Hawai'i inversion layer is associated with a consistent area of high pressure (sinking air) in the eastern Pacific that is part of the global atmospheric circulation system.

(5) The mountains around Los Angeles also contribute to the smog problems there.

REFERENCES:

Suhadi, D., Awang, M., Hassan, M., Abdullah, R., and Muda, A. 2005. Review of Photochemicla Smog Pollution in Jakarta Metropolitan, Indonesia. American Journal of Environmental Sciences 1:2, pp110-118.