Introduction
The North Atlantic hurricane season officially started on June 1st, before which date, all winds were zephyrs. The Northeast and Central Pacific season started on May 15th. Every major ocean has its season, and these signify a degradation in satellite communication. In this article, we look at the impact this will have on maritime users.
Hurricanes are the tropical storms that form over the North Atlantic Ocean and the North east Pacific between June and November. Over the South Pacific and Indian Ocean, these are called cyclones characterised as lasting from April to December. The Northwest Pacific Ocean has typhoons between May and October, climate change permitting. All these storms are full of hot air and rain.
The Antarctic Ocean is exceptional in that it has storms all year round getting more ferocious the further south, so these latitudes are called the Roaring Forties, Furious Fifties and Screaming Sixties.
Most meteorological agencies are forecasting a doozy of a hurricane season in 2024 because of record sea water temperatures (that’s where the energy for the hurricanes comes from). The extent of the 26°C sea surface temperature (SST) isotherm (the areas which support tropical cyclone development) is across much of the tropical North Atlantic and Caribbean Sea; the largest at this time of year since 2010. This is exacerbated by La Niña in the equatorial Pacific Ocean which, whenever it arrives, will intensify hurricanes in the North Atlantic.
The map below shows all categories of marine heatwaves for March 26, 2024, for the entire global ocean – GLO12 analysis.
(Source: Mercator Ocean International)
There are several other minor variables to add to the mix such as the North Atlantic oscillation (NAO), the horizontal flow of the dry, dusty Saharan air layer (SAL), and the Madden-Julian oscillation (MJO) which is increased rainfall in the Indian Ocean and affects the generation of hurricanes in the North Atlantic. The upshot of this is lots of wind and rain between August and October for ships trading across the North Atlantic. It is certainly worrying the maritime insurers.
How Does This Affect Maritime Satellite Communication?
The reason that big storms affect maritime satellite communication is that moisture and other gases and dust in the atmosphere absorb the energy carried in the radio waves. This is generally termed ‘rain-fade’. The reality is a tad more complicated but, essentially, the gas molecules of water in the atmosphere are similar size to the wavelength of the communication and absorb the energy of the transmission leaving an attenuated signal to reach the dish antenna.
The atmosphere has many gas molecules and dust particles, all of which have the potential to absorb communication energy. Luckily, although present enough to weigh down on our bodies at atmospheric pressure, they are relatively sparse leaving lots of room for communication to get through. During heavy storms, such as hurricanes, the water vapour aggregates to such an extent that the space between vapour molecules is less and wavelength energy is absorbed.
Atmospheric water vapour absorption peaks around 22.3 GHz, although it continues to absorb at higher frequencies making K and Ka-band more susceptible to any type of atmospheric moisture. The Ku band is less susceptible, but not entirely free from absorption. L-band is fairly clear in this regard. Additionally, the leading edge of a storm can cause electromagnetic interference. In general, the higher the frequency, the deeper the fades can be.
(Source: https://www.esa.int/)
Providers have addressed this problem by increasing power of transmission and modulating signals and communication is better than it was, but still suffers for maritime users. Tropical storms such as hurricanes are huge. They can be several hundred miles across, so high speed communication can become hit and miss for prolonged periods.
Longer wavelengths are less susceptible to rain fade, with the trade-off being they’re not able to carry as much data. The L-band network is used for global maritime and aviation safety services and is also used for navigation, including GPS and satellite radio systems. Modern data links can achieve up to 10 Mbps although 1 Mbps and lower are far more common.
Ka band data download transmission rates can be 300 Mbps under test conditions although download speeds up to 50Mbps and up to 5Mbps for upload are advertised.
These transmission rates are significant for more than downloading HD movies. For autonomous shipping and stationary vessels, such as offshore platforms using cloud-based AI, assistance may require three hundred times the transfer rate. This is an exaggerated statement, but remote AI can require significant data transfer and consume significant amounts of power. It makes sense for as much AI as possible to be on-board. Qualcomm already has chips incorporating AI capability and advertised as power efficient.
Summary
Major tropical storms such as hurricanes are a danger to merchant vessels and offshore platforms, putting their crews, cargoes, processes and marine ecosystems at risk if they capsize or founder. During these storms, vessels will normally have good L-band service for safety services, navigation and GPS. Legacy L-band services such as Iridium satellite phones will still work properly.
When it comes to high throughput applications that utilise the higher wavebands, Ku and Ka, then there exists the possibility of disruption. The use of adaptive power control, which is the most effective weather mitigation tool allowing increase of signal strength to try to ‘burn’ through the storm, and adaptive modulation using advanced signal processing algorithms to reinforce data transmission, can help, but are not totally fool proof.
In all likelihood, hurricane seasons and their other ocean counterparts will become more problematic as climate warming really starts to bite. Maritime operators need to plan for this future, and it might make sense to embed as many AI functions as possible on-board so that slower satellite bands can take up the workload as higher wavelengths suffer from weather related phenomena.
The future of maritime connectivity and the future of autonomous maritime vessels will be a core focus of Valour’s upcoming syndicated reports. The former is due to be published July 2024 and will analyse the current and future marketplace for mobile operators, ISPs, maritime service providers and cellular hardware manufacturers. The latter will examine the emerging market for autonomous maritime vessels, detailing technical requirements. To learn more, download our report information brochures here.
