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KEESLER AIR FORCE BASE, Biloxi, Miss. -- A team with the Naval Academy's Training and Research in Oceanic and Atmospheric Processes in Tropical Cyclones, or TROPIC, internship program completed six weeks of ocean operations and research with the Air Force Reserve's 53rd Weather Reconnaissance Squadron Hurricane Hunters Aug. 31.
This was the fifth summer a TROPIC team deployed with the Hurricane Hunters to gather storm data in the Atlantic and Pacific Oceans, which is used to determine how the relationship between the ocean and a hurricane can improve forecasts of storm track and intensity.
"The Navy research team is trying to help answer the problem of forecasting tropical cyclone intensification which is one of the biggest forecast challenges facing the forecasters and computer models which forecast storm intensity over time," said Lt. Col. Jon Talbot, 53rd WRS chief meteorologist. "The team has been dropping ocean sensors around these storms, from our aircraft, to get a better understanding of the ocean heat content; how deep and warm the ocean is around hurricanes and tropical storms. In several cases, the data has shown to be beneficial to the computer models in helping make this intensity forecast better."
Most hurricane prediction models evaluate conditions in the atmosphere, said Navy Cmdr. (Dr.) Elizabeth Sanabia, a permanent military professor in the Naval Academy's Department of Oceanography. They include ocean surface temperatures, but rely primarily on predicting changes in the atmosphere to determine a hurricane's future track and intensity. Without factoring in changes in the ocean, the air-sea link is challenging to get right, because it is hard to know how much heat is transferred between the ocean surface and the atmosphere, she added.
"The oceans are an energy source for hurricanes," Sanabia said. "They provide heat and moisture to the atmosphere, which makes the air more buoyant and results in greater convection that promotes strengthening of a storm."
Several organizations, including the Navy and the National Weather Service, have developed "coupled" numerical forecast models, which include atmosphere, ocean, and wave information to improve hurricane prediction.
"In 2008 and 2010 the Navy worked with 53rd WRS in the Western Pacific to research the impact of the ocean on the intensification of tropical cyclones, and it was shown then that with enough information about the ocean, the coupled models could produce more accurate forecasts" said Sanabia. "The focus now is to translate that research success into an operational one.
While the Hurricane Hunters gather real-time storm data such as wind speeds and central pressures for forecasters at the National Hurricane Center and Central Pacific Hurricane Center, the navy team deploys specialized ocean instruments, Airborne eXpendable BathyThermographs, or AXBTs, during the Hurricane Hunter missions to capture the temperature of the ocean beneath the storm. The buoys send data by a radio signal from the ocean surface while diving down 800 meters into the water.
"We get a temperature profile; and we can look at how deep the mixed layer is, the warm layer at the surface, and how the temperature changes with the depth," she said. "If you were to equate it to a car, the heat in the ocean would be like the gas in the car's gas tank. The hurricane winds at the ocean surface act as the gas pedal to move that heat energy to the atmosphere and intensify the storm - the higher the wind speed at the surface, the more gas, or ocean heat, is extracted from the tank. It helps to know how much fuel is available for the storm."
Last year, researchers had a unique opportunity to collect data on Hurricanes Julio and Iselle, which were back-to-back hurricanes that followed a similar track in the Pacific; said Sanabia.
"When we flew Iselle and Julio, the data we collected from the AXBT observations did more to correct the ocean models than any other observation in the Pacific Ocean during the same period," she said.
Most observations over the oceans are from satellites, which primarily measure temperature at the sea surface, Sanabia said. The AXBTs measure temperature well below the surface and correct the initial conditions in the model.
"If we can give the model a better set of information to start with, the forecasts the models produce will be better as well," said Sanabia.
Actual improvements to the Navy's coupled numerical model are evaluated by a team at the Naval Research Laboratory in Monterey, California, who receive and use the data collected by the TROPIC team.
"These evaluations are complex and take a great deal of time," Sanabia said. "To date, the team has evaluated results in four storms over the past four years .There has been an improvement each time, either in track or intensity or both. Improvements are slight sometimes, but they are always there."
This year the team focused on incorporating a new instrument into their observation plan. Along with colleagues from the Woods Hole Oceanographic Institute, the team deployed several Air-Launched Autonomous Micro-Observer profiling floats, commonly referred to as ALAMO, which are similar in size, shape and weight to the AXBT, but have several important improvements, said Sanabia.
"While each AXBT is capable of measuring the ocean column temperature one time, the ALAMO can measure 1,000 temperature profiles," she said. "Also, while AXBTs rely on fall-rate equations to measure depth, the ALAMO directly measures pressure (a proxy for depth), which increases the accuracy of the observation. The increased number of observations from a single buoy also enables the researchers to better understand the response of the ocean, while still contributing to the hurricane forecast improvement."
"We are interested in how the ocean responds in different areas of the storm," she said.
While the overall goal of the project is to improve forecasts using ocean data, some parts of the research change from year to year. These research projects are tackled by the Midshipmen. Navy Ensign Sara Reynolds graduated from the Naval Academy in May and completed her third year with the 53rd WRS. She deployed to Hawaii last year to fly Iselle and Julio, and presented her senior research project on those storms in December.
She studied how the outflow patterns, the clouds that move away from the storm, can impact the intensity of a storm, she said.
"Because Hurricanes Julio and Iselle followed a similar path, there was a lot of control: same area; same basin; same general timeframe. Both storms were impacted by the subtropical jet to the north of the storm, but in different ways. It was interesting to study the similarities and differences between the storms."
The Midshipmen not only gain valuable research experience, but they get to see how an operational squadron works, said Reynolds.
"I enjoy seeing how the squadron operates: what work goes into a deployment, how the flights and schedules are managed. I also enjoy seeing real world benefits of what the squadron is doing and how our research is able to fit in and help the models," she said.
| Date Taken: | 08.31.2015 |
| Date Posted: | 11.23.2016 16:07 |
| Story ID: | 215763 |
| Location: | KEESLER AIR FORCE BASE, MISSISSIPPI, US |
| Web Views: | 45 |
| Downloads: | 0 |
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