HOUSTON – Did you see us showing Friday morning’s explosion in northwest Houston on the radar? The fact that the explosion could be identified with radar shows how intense it really was. Here is the science behind how that happened.
What is radar?
Radar is an invisible beam of energy that bounces off water droplets in the atmosphere and sends back a signal that meteorologists can interpret as different types of precipitation, depending on which signals are received. The cool thing is that radar beam not only bounces off water droplets but it also bounces off of everything. This makes radar a very powerful tool. Meteorologists use radar to not only show where it is raining, hailing or snowing but it can also be used to study everything from bird and bat migrations to, yes, identifying where we have debris in the air from storms or explosions.
How do meteorologists show debris using radar?
Meteorologists use a parameter on radar called “correlation coefficient” when looking for debris signatures. It’s a measurement of how uniform features are on the radar. Lower values indicate a concentration or cluster of particles that have different sizes. These lower values typically do not represent precipitation. Instead, these clusters usually indicate debris that is floating in the air.
When do meteorologists typically use the correlation coefficient in forecasting?
Meteorologists usually use this parameter when trying to determine if a rotating radar signature (like a thunderstorm) has actually dropped a tornado. If a tornado is on the ground and it is big enough, a debris ball can sometimes be spotted using the correlation coefficient parameter. This gives meteorologists confirmation that a tornado is in fact on the ground. This is extremely helpful when there is no visual confirmation of a tornado. It can also be used to help determine the intensity of a tornado. The more visible the signature, the more debris there is and, therefore, the larger the tornado.