Everybody knows the atmospheric turbulence, which among other things cause those annoying and disturbing jumps when we travel by plane. In fact, these disturbances are responsible for 71% of the injuries that occur on board, usually of a minor nature. Now, as scientists from the University of Reading (United Kingdom) have discovered, the frequency and intensity of these turbulences are set to increase in the coming years due to global warming. It is time, therefore, to fasten the seat belts.
Although winter is the most conducive season for turbulencecomputer models suggest that by the year 2050, summers will register the same intensity of this phenomenon as the winters of 1959.
The article that includes the results of the research, entitled ‘Clear air turbulence trends over the North Atlantic in high-resolution climate models’, has been published in the international journal Climate Dynamics.
Clear Air Turbulence (CAT) is one of the most damaging weather-related hazards. It usually develops in cloud-free environments of the upper level atmosphere. Offering no visual cues to pilots and being undetectable by onboard radar, these events seem to appear out of nowhere.
In fact, prolonged exposure to this type of atmospheric disturbance shortens the life of the ship and the time it can be in service. Aircraft equipment can be damaged and even serious structural damage can occur due to more intense than usual turbulencehe. In extremely rare cases, it could even fracture the plane. During moderate turbulence, items of cargo, luggage, or passengers themselves may shift and cause damage or injury.
In December 1997, a Boeing 747 flight UA826 operated by United Airlines encountered a CAT event en route from Tokyo to Hawaii. The Boeing moved upward at 1.8 times the force of gravity, sideways moved at 0.1 g, and six seconds later the aircraft descended rapidly, causing a negative g-force of -0.8 g. As a consequence, one passenger died and others suffered serious injuries. The plane, for its part, had to be withdrawn from service a year before the scheduled deadline.
Transatlantic air travel often encounters CATs due to the presence of the mid-latitude eddy-driven jet stream over the North Atlantic. According to the researchers, CAT events take place in regions of instability driven by the so-called ‘shear effect’ of the atmosphere. They often occur in upper-level jet streams, narrow bands of strong winds that have a strong seasonal dependency.
14% more for each degree of heating
The intensity of a jet stream depends on latitudinal horizontal temperature gradients. Due to a series of temperature changes between the pole and the equator, Jet streams are expected to intensify in the ‘wind shear’ effect with human-induced climate change.
To analyze this phenomenon, the study used three global climate modeling simulators covering the period 1950–2050. By combining these models with 21 mechanisms for turbulent airflow, the researchers created a wide range of CAT-generated scenarios.
According to this research, for every 1°C of near-surface global warming, moderate CAT events will increase by 14% in summer and fall and 9% in winter and spring. Moderate turbulence is understood as inflicting vertical accelerations of up to 0.5g.
In an earlier study by Paul D. Williams, professor of atmospheric science in the Department of Meteorology at the University of Reading, it was predicted that these events would increase between 40% and 170% over the North Atlantic if pre-industrial atmospheric CO2 concentrations doubled.
Since turbulence will increase in all seasons, current flight routes will have to deal with more of these annoying situations. One option for airlines may be to try to avoid areas where CATs form. This could result in longer transatlantic flights and would also result in thousands of additional hours of accumulated fuel costs.
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