© University of Reading st ECATS conference November 2013 The impact of climate change on trans-Atlantic aircraft routing Emma Irvine, Keith Shine, Brian Hoskins, Marc Stringer Meteorology Department, University of Reading 1

Motivation For trans-Atlantic flights the jet stream influences the optimal flight route location, time and its climate impact Climate change may alter characteristics of the jet stream, such as the mean and variability of its location and wind speed Aims of this work: 1.What are the predicted changes to the north Atlantic jet stream by 2100? 2.How do these changes impact trans-Atlantic flights? 2

Eastbound: New York - LondonWestbound: London – New York 0000 UTC 09 Dec UTC 09 Dec 2009 Minimum time route North Atlantic Tracks (defined daily by air traffic control) Trans-Atlantic aircraft routes are weather dependent

Eastbound: New York - LondonWestbound: London – New York 1200 UTC 19 Dec UTC 19 Dec 2009 Minimum time route North Atlantic Tracks (defined daily by air traffic control) Trans-Atlantic aircraft routes are weather dependent

Great circle distance 370 min in still air New York London Trans-Atlantic aircraft routes are weather dependent

Minimum time routes are provided twice-daily by the Met Office, run on 40 km resolution winds at 250 hPa. Route extension = Minimum time route distance – great circle distance Westbound 12 UTC Eastbound 00 UTC Daily Minimum time routes, Dec Trans-Atlantic aircraft routes are weather dependent

Winter weather types are characterised by the jet stream Eastbound Westbound Irvine et al., 2013, Met. Apps. 7 W1. strong zonal jet W2. Strong tilted jet W4. Confined jet Composite 250 hPa geopotential height (black) and wind speed > 40 ms -1 (red). Individual minimum-time aircraft routes between London and New York (blue).

W1 W2W4 Route time and jet stream

W1W2 W4

Projected climate change We analyse the very high greenhouse gas emissions scenario (RCP8.5, red line) over the period IPCC, 2013

Frequency of jet stream winds in EC-EARTH climate model (CMIP5) No change to mean jet latitude (48.4 ºN in both simulations) Small increase in mean jet speed (43.9 to 45.5 ms -1 ) 11 Winter Winter

London-New York route latitude Current climate (solid line) and future climate (dashed line) Negligible effect of wind changes on route location 12 Eastbound Westbound

London-New York route time Current climate (solid line) and future climate (dashed line) Only small changes to mean route time 13 Eastbound dt = -2 min Westbound dt = +1 min

Conclusions For trans-Atlantic flights, both the aircraft routing and subsequent climate impact are weather dependent For one CMIP5 climate model, EC-EARTH, for the period relative to present-day we find: Small changes to the jet stream No significant changes to either route location or time for the analysed city-pair (London – New York) Results are likely to be sensitive to the choice of climate model and emissions scenario Future work will analyse contrail conditions in the future climate

Thank you! Information from: 15

Minimum-Time Routing Code Based on method in Lunnon and Marklow (1992), that is implemented at the UK Met Office From Sawyer, 1949: For a given wind field, the minimum-time path is given by solving: (Rate of change of aircraft heading θ = rate at which tailwind u varies in direction perpendicular to aircraft) 16