Impact of the North Atlantic Oscillation on Transatlantic Flight Routes and Clear-Air Turbulence

Abstract

The variation of wind-optimal transatlantic flight routes and their turbulence potential is investigated to understand how upper-level winds and large-scale flow patterns can affect the efficiency and safety of long-haul flights. In this study, the wind-optimal routes (WORs) that minimize the total flight time by considering wind variations are modeled for flights between John F. Kennedy International Airport (JFK) in New York, New York, and Heathrow Airport (LHR) in London, United Kingdom, during two distinct winter periods of abnormally high and low phases of North Atlantic Oscillation (NAO) teleconnection patterns. Eastbound WORs approximate the JFK–LHR great circle (GC) route following northerly shifted jets in the +NAO period. Those WORs deviate southward following southerly shifted jets during the −NAO period, because eastbound WORs fly closely to the prevailing westerly jets to maximize tailwinds. Westbound WORs, however, spread meridionally to avoid the jets near the GC in the +NAO period to minimize headwinds. In the −NAO period, westbound WORs are north of the GC because of the southerly shifted jets. Consequently, eastbound WORs are faster but have higher probabilities of encountering clear-air turbulence than westbound ones, because eastbound WORs are close to the jet streams, especially near the cyclonic shear side of the jets in the northern (southern) part of the GC in the +NAO (−NAO) period. This study suggests how predicted teleconnection weather patterns can be used for long-haul strategic flight planning, ultimately contributing to minimizing aviation’s impact on the environment.

Aviation Turbulence: Dynamics, Forecasting, and Response to Climate Change

“…This is one of the reasons for the success in forecasting turbulence of CAT diagnostics containing vertical wind shear [e.g., Colson-Panofsky index (Colson and Panofsky 1965), TI1, TI2 (Ellrod and Knapp 1992)]. Kim et al (2016) studied the impact that the North Atlantic Oscillation (NAO) has on aviation turbulence. The NAO is a measure of the relative strength of the Icelandic low and the Azores high.…”

“…This change to the jet stream, therefore, has an impact on turbulence for transAtlantic flights. Kim et al (2016) used wind-optimal routes to find the fastest possible flight path between London (LHR) and New York (JFK). The study found that eastbound flights fly more frequently through regions of CAT than westbound flights, and, therefore, experience more turbulence in both the positive NAO phase and the negative NAO phase.…”

“…According to Kim et al (2016), in the positive NAO phase, westbound flights experience more moderate-or-greater (MOG) CAT than in the negative NAO phase, because some of the westbound flights detour northward to be on the cyclonic shear side of the northerly shifted jet stream, which is more susceptible to MOG turbulence. In contrast, eastbound flights in the negative NOA phase fly through the cyclonic shear side of the southerly shifted jet.…”

Aviation Turbulence

“…And the turbulence potential along these trajectories also highly depends upon these weather conditions, because local gradients of meteorological variables like horizontal and vertical wind and temperature are generally large within the jet stream (e.g., Kim et al 2016). …”

Update of upper level turbulence forecast by reducing unphysical components of topography in the numerical weather prediction model

“…Unexpected turbulence encounters at cruising altitudes of z = 8 ~ 12 km are a leading cause of weather hazards for the aviation industry and may cause in‐flight injuries, flight delays, and structural damage [e.g., Sharman et al , ]. Turbulence in the absence of adjacent deep convection is normally referred to as Clear‐Air Turbulence, which often occurs near the upper level jet and frontal system due to shear instability, inertial instability, and geostrophic adjustment or spontaneous imbalance [e.g., Endlich , ; Dutton and Panofsky , ; Shapiro , ; Ellrod and Knapp , ; Knox et al , ; Kim et al , ]. Upper level turbulence can also occur over the complex mountainous regions mainly due to the interactions between mountain waves and the background wind, which is known as mountain‐wave turbulence (MWT) [e.g., Lane et al , ; Kim and Chun , , ; Sharman et al , ].…”