Thursday, June 11, 2009


I've been not posting about Air France 447 for a reason: because it's hard to say what actually caused the crash. I've ready a lot of articles about the tragic flight, and many of them cite weather as one possible cause. There is chance that we'll never know what exactly happened. But there is a still a chance that the weather was at least a factor. I've heard from multiple sources that storms were in the area at the time of the crash.

A recent article on highlights not the specifics of AF447, but rather the general dangers of the region that the flight was traveling through. This region around the equator is called the Intertropical Convergence Zone, or ITCZ. This region near the equator is known for persistant thunderstorms. It is a ring of low pressure that wraps around the globe. This low pressure allows parcels of moist, unstable air to rise, forming thunderstorms. If you look at a global satellite picture, you will likely see these thunderstorms in a broken line through the tropics. This time of year, with more sunlight falling on the northern hemisphere, the ITCZ is to the north of the equator. During the northern hemisphere winter, it is located to south of the equator.

What can make this region dangerous to flying is the height that the storms reach. At their peak, thunderstorms cap off at the tropopause. This is the reason that anvil heads are prevalent for large storms. The rising, unstable air reaches the stable boundary between the troposphere and the stratosphere and is stopped in its tracks. The clouds can't rise, so it stretches out in the direction that the upper level winds are blowing. This happens in the ITCZ as well, only the stable layer is much higher. The tops of these storms can reach up to 50,000 feet, higher than commerical planes can fly. As a result, if a pilot cannot avoid the thunderstorm and fly around it, they may need to fly through it. Within the storm, the plane will feeel a lot of turbulence because of rising and falling air within the thunderstorm, as well as the possibility of frequent lightning and hail. Weather radar equiped on all aircraft helps pilots avoid the worst of it. And better technology for everything from forecasting to the design of aircrafts mean that flights can fly through the ITCZ without issue.

No comments: