Saildrones Go Hurricane A-Hunting – Inside Unmanned Systems

This summer, five orange Unmanned Surface Vessels (USVs) departed the U.S. Virgin Islands, fitted with heavy-duty hurricane wings to operate in winds over 70 mph and waves over 10 feet. Their destination: the heart of the tropical storms that ravage the Atlantic. Their mission: to collect scientific data where it has never been collected before.

Saildrones, manufactured by the company of the same name based in Alameda, Calif., Are autonomous ocean-going vessels designed to study the environment. They are very manoeuvrable, wind and solar powered vehicles designed for long range data collection missions. They collect weather and environmental data above and below the sea surface and can withstand the extreme winds and sea conditions present during a hurricane. The hurricane model is 23 feet long and has four cameras, a dual GPS with inertial measurement unit (IMU) and several other sensors (see diagram at the bottom of this article).

Saildrone USVs are under the constant surveillance of a human pilot via satellite and navigate autonomously from one waypoint to another, taking into account the wind and currents, while remaining in a safety lane defined by the ‘user.

The Pacific Marine Environment Laboratory (PMEL) and the Atlantic Oceanographic and Meteorological Laboratory (AOML) of the National Oceanic and Atmospheric Administration (NOAA) collaborate on hurricane-hunting missions. This summer, the Saildrones took up positions in areas of the Atlantic Ocean that have historically experienced a large number of storms. Scientists from PMEL and AOML worked together to pilot the vehicles through a series of hurricanes for testing and sampling. This mission created a foundation for PMEL and AOML to deploy a larger fleet of saildrones as part of a major field campaign for hurricane watching.

The biggest hurricane forecasting challenge is the rapid intensification, which can have a huge impact if a storm intensifies just before it makes landfall. Hurricane Ida, which hit the Gulf Coast before making its way to the northeast recently, went from a Category 1 storm to a Category 4 storm in less than 24 hours. Scientists need to understand the oceanic processes that occur as intensity increases, which means collecting data immediately before and during a hurricane.

A tropical cyclone is an umbrella term for a rapidly rotating tropical storm with a center of low pressure and clouds moving towards the center of the system. In the Atlantic, they are also called hurricanes; in the Pacific they are called typhoons.

The NOAA Climate Prediction Center has predicted a 60% chance that the 2021 Atlantic hurricane season will be above normal, with 13 to 20 named storms. About half of them are expected to become hurricanes, and 3 to 5 of them are expected to become major hurricanes, category 3 or higher.

“The biggest gap in our understanding of hurricanes is in the processes by which they escalate so rapidly, as well as the ability to accurately predict their strength. We know that the heat exchange between the ocean and the atmosphere is one of the key physical processes providing energy to a storm, but to improve understanding we need to collect in situ observations during a storm. Of course, this is extremely difficult given the danger of these storms. We hope that the data collected with the saildrones will help us improve the physics of the model, and then, in turn, we can improve the prediction of hurricane intensity, ”explained Dr. Jun Zhang, scientist in the Research Division on the NOAA / AOML hurricanes. .

The 23ft Saildrone Explorer is typically fitted with a 16.5ft (5m) rigid wing for forward propulsion. This wing is optimized for a wide range of sailing conditions, from very light to moderately strong wind speeds. In November 2020, Saildrone began a five-month test of the first, shorter, hardened cyclonic wing in an area of ​​the North Pacific where winter storms are frequent. Proven, this model sailed the Atlantic hurricane season in the summer of 2021.

??[Image above: Saildrone Explorer equipped with a hurricane wing,  is a shorter, ruggedized wing optimized for tropical storm wind events Category 1 (74–95 mph/118–151 km/h) and above on the Saffir-Simpson Hurricane Wind Scale. All images courtesy Saildrone.]

The USVs transmitted real-time meteorological and oceanographic data from the eastern tropical Atlantic, including air temperature and relative humidity, barometric pressure, wind speed and direction, temperature and salinity of water, sea surface temperature, and wave height and period. The data was also sent to the Global Telecommunications System (GTS) of the World Meteorological Organization (WMO) and disseminated to all major forecasting centers, some 20 agencies around the world, including NOAA.

The data will also be valuable to other groups, including the National Weather Service (NWS) and the National Environmental Satellite, Data and Information Service (NESDIS). NWS will use Saildrone data to improve forecasting. NESDIS will align findings from Saildrone data with those from other observation platforms, such as gliders.

Saildrone has built around 100 ships and plans to build more, including larger vehicles. The company’s USVs have logged more than 10,000 days at sea and 500,000 nautical miles from the Arctic to the Southern Ocean. In addition to the Atlantic hurricanes, Saildrones is engaged this year in other studies in the Atlantic, the Pacific, the Great Lakes and a year-round mission to study air-sea carbon dioxide exchanges in the Gulf Stream.

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