The Science Of Bathymetry

Good morning again. The other night, I was watching the Weather Channel, and caught some of Abrams and Bettes: Beyond the Forecast. The show was obviously dealing with the situation around Hurricane Ike as it was back over water in the Gulf of Mexico, and forecasts were beginning to point to a Texas landfall. During the discussion on Ike, the topic of waves and surge came up.

Stephanie Abrams pointed out that the waves and surge were inversely related. In other words, places that usually get high waves also get lower surge while the converse is true for places that get low waves. She then went on to use the Gulf Coast as an example. Along the Texas coast, waves are usually high, but the surge is low. Meanwhile, in Louisiana, the converse was true. Waves are low, and the surge is high. Abrams, who joined TWC in 2003, and gained notoriety with her coverage during the 2004 and 2005 Hurricane Seasons according to her bio on weather.com, then mentioned the term, Bathymetry.

At that point, I became curious so the following morning, and even a bit today, I looked up the term Bathymetry on Google, and found an entry for it on Wikipedia. The definition of the word according to the site is the following: The study of underwater depth, of the third dimension of lake or ocean floors. Wikipedia goes on further to state that it is the underwater equivalent of Hypsometry, which is the measurement of land elevation relative to sea level. Orignally, bathymetry was the measure of ocean depth. In the early days of this science, pre-measured heavy rope or cable lowered over a ship’s side was a technique that was used, but it was limited in the sense that “it measures the depth only a single point at a time, and so is inefficient. It is also subject to movements of the ship and currents moving the line out of true and therefore is inaccurate.”

Today, a much more efficient method is used, and that is using sonar. According to Wikipedia, which takes this information from a book called Remote Sensing in Air and Space, the data used to make bathymetric maps today typically comes from an echosounder mounted beneath or over the side of a boat, “pinging” a beam of sound downward at the seafloor or from remote sensing LIDAR or LADAR systems.” How does this relate to hurricanes? Well, in the sense that the shape and the depth of the coastline has an impact on how bad the surge will be. There are other factors too such as wave heights, sustained winds, and barometric pressure, but a shallow or deep coastline also plays a pivotal part in how much surge a location will get when the strongest portion of a hurricane comes ashore.

Researching the topic of Remote Sensing a bit more, I discovered that the Meteorology Department at Rutgers offers a course in the study of Remote Sensing in the Oceans and Atmosphere. The description of the course is as follows: Methods, instruments, and their application to obersvations of ocean and atmosphere. Sensing of oceanic parameters such as temperature, salinity, currents, sea state, turbidity and pollutants, etc. I believe that this course was offered as an elective for the Meteorology Minor that I earned when I was at Rutgers, but I never took the course.

Sciences like this, and Paleotempestology are fascinating ones to look at, and investigate. I had planned writing an article on Paleotempestology last year, but as many of you have probably seen at the site, I haven’t quite gotten around to it yet. I hope so soon. Nevertheless, I did enjoy the discussion on TWC the other night, and it gave me a better understanding of how the ocean behaves along certain coastlines, and why storm surge values can be so much different depending upon where the storm ends up.