Weather Watch

Sound can travel great distances depending on weather conditions

Special to The TribuneJanuary 4, 2014 

This photo was taken Friday morning and shows white pelicans and cormorants at Morro Bay. You could hear these birds miles away.

JOHN LINDSEY

My 10-year-old son Sean and I went kayaking on Morro Bay on a hazy and windless day from Baywood Park pier. On that morning you could hear many different sounds traveling across the bay: The laughter of people on Morro Bay’s sand spit, the barking of sea lions from the Embarcadero, strange guttural sounds of cormorants near the Morro Bay estuary along South Bay Boulevard, crashing waves.

On that morning the atmosphere was acting like a seashell. You see, seashells capture the ambient noise from the environment. The sound resonates inside the shell and produces a wavelike noise; no matter how far away one is from the ocean. The walls of the seashell capture and direct sound to our ears.

When the weather conditions are right, the sounds from the bay are captured much like the seashell. Let me explain — when the air is calm and still, most likely in the morning, the cool and dense air sinks toward the Earth's surface and produces a temperature inversion layer. This layer of cool and dense air produces a sound channel much like the walls of the seashell.

This temperature inversion layer can range from a few feet above the ocean surface to hundreds of feet high. When the inversion layer is at the right height, the sound of the waves breaking on the sand spit can easily be heard throughout Los Osos and Morro Bay. The sounds of laughter or calls of birds reflect or skip off the inversion layer toward the water.

In other words, the sounds of the bay are captured in the surface channel and propagate toward the shoreline with little loss in intensity, so that the folks on the sand spit sounded as if they were standing just a few feet away.

Due to this winter’s lack of storms these tranquil conditions have become much more common. At other times, the winds blow fast enough to mix up the temperature inversion layer, allowing the sound to spread out in all directions, with a much greater loss in sound intensity. That makes it seem quieter regardless of the amount of sound from wildlife or persons. You could say the sound of their voices was lost on the wind.

 

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John Lindsey’s column is special to The Tribune. He is a media relations representative for PG&E and a longtime local meteorologist. He is president of the Point San Luis Lighthouse Keepers. If you have a question, send him an email at pgeweather@pge.com.

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