© University of Reading 2011 www.met.reading.ac.uk/~gb902035

TRI-Napier and RMetSoc Conference Sept 2011

Exploring the feasibility of climate-optimised flight routingEmma Irvine, Keith Shine, Brian Hoskins

Meteorology Department, University of Reading

Contact: e.a.irvine@reading.ac.uk

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Outline

• Motivation for climate-optimised routing– The climate impact of aviation emissions

• The REACT4C project

• Results: Weather and aircraft routing in the N Atlantic– The role of the jetstream and NAO– Identifying weather types for the North Atlantic– Does the climate impact of the emissions vary by type?

• Conclusions and future directions

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Radiative forcing resulting from aviation emissions

Timescale Weather Less relevant

Hours More relevant

• Aviation emissions contribute 3.5% (range 2-14%) of total anthropogenic forcing, including non-CO2 effects (Lee et al., 2009)

Months

Decades

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Motivation

Lee et al (2009) From Laura Wilcox

Growth in global CO2 emissions Altitude of aircraft emissions

1. Climate impact is not just from CO2

2. Climate impact is disproportionate to quantity of emissions

3. Climate impact will increase – sector growing at 5% per year

4. Aviation Industry targets: 50% reduction in net CO2 emissions by 2050: technological and operational measures

9-12km

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• Minimize the climate impact of the aircraft’s emissions

• Traditional constraints: time, cost, fuel

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Advantages: Potential Difficulties:

Low-cost Air-traffic control constraints

Quick to implement High volume of air traffic in N. Atlantic

Does not rely on technological developments

Requires highly accurate weather information (IAGOS helpful)

Climate-optimal aircraft routing

New York London

• North Atlantic Tracks

• Minimum separations:– 1° latitude between tracks– 1000 ft vertical– 10 min along-track

• Specified twice daily by ATC based on airline requirements:

– Eastbound at night– Westbound during day

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Climate-optimal aircraft routing

New York

London

Dec 2009

westbound

eastbound

Climate impact varies with route location, weather and season

18 February 2010 26 January 2010

Flight entirely in stratosphere produces no contrails

Flight mostly in troposphere produces persistent contrails

Flight level

tropopause

contrails

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EU REACT4C Project

• EU FP7 medium-scale collaborative project

• NOT implementing or developing capability to implement!

• Results due END 2012

2006 aircraft emissions (Laura Wilcox)

North Atlantic Flight Corridor

• 6.5% total aviation CO2 emissions

• 97% emissions released above 7km (Wilkerson, 2010)

GOAL: Assess the feasibility of reducing emissions of trans-Atlantic flights through climate-optimal routing

8Website: www.react4c.eu

Climate optimal routing in the EU REACT4C project (1)

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READING/MET OFFICE

DLR/CICERO/MMU/AQUILA

EUROCONTROL

• Calculate the climate-optimal route for separately for each flight across the north Atlantic (~300 per direction per day)

• Aircraft specifications:• current operational fleet• future green aircraft (AIRBUS)

Climate optimal routing in the EU REACT4C project (2)

EUROCONTROL

• Not all aircraft will be able to fly their climate-optimal route

• Iterate to find a combination of climate-optimal and sub-climate optimal trajectories which results in:

• Reduced total climate-impact of NAFC traffic compared to a control scenario (minimal fuel use)

• An acceptable workload for ATC

• Answer will be different for each weather situation!

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Defining typical weather patterns over the north Atlantic

Paper in review:

Irvine et al., 2011, Characterising north Atlantic weather patterns for climate optimal aircraft routing, Meteorological Applications

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Time-optimal route latitude is related to the jet stream latitude

EASTBOUND WESTBOUND

Jet stream latitude is related to NAO and EA patterns (Woollings et al. 2010) 12

The jet stream latitude is related to the North Atlantic Oscillation

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+ve

-ve

From: http://www.ldeo.columbia.edu/res/pi/NAO/

NAO +ve = northerly jet stream NAO -ve = southerly jet stream

ERA-Interim meteorological re-analysis data from 1989-2010

Winter weather types are characterised by the jet

1. Strong zonal jet

2. Strong tilted jet

3. Weak tilted jet

4. Strong confined jet

Eastbound Westbound

Irvine et al., 2011, Met. Apps., submitted14

Winter weather types are characterised by the jet

1. Strong zonal jet

2. Strong tilted jet

3. Weak tilted jet

4. Strong confined jet

Eastbound Westbound

Irvine et al., 2011, Met. Apps., submitted15

Climate impact varies byweather type and route direction

CO2 Contrails

Jet classification: S=strong, W=weak, Z=zonal, T=tilted, C=confined

We define indicative proxies for the climate impacts (other REACT4C partners will do detailed calculations for):

• CO2 route time• Contrails distance contrailing• NOx route time at each latitude• H2O route time in stratosphere

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Probability of making a persistent contrail along a route at different flight levels

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• Cruising at higher altitude decreases contrails (e.g. Fichter, 2009)• Not true if you look at individual weather types!

Summary

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• For the North Atlantic, distinct weather types are identified, each associated with different winds and time-optimal routes

• Both the route location and climate impact are determined by the meteorology

• The climate impact relates to the route length (CO2), latitude (O3),

height relative to the tropopause (H2O) and regions of ice-

supersaturation (contrails)

• The climate-optimisation strategy depends on the relative weighting of the climate impacts

Is climate optimal routing a feasible way of reducing emissions of trans-Atlantic flights? Wait and see: REACT4C results due 2012

Future Directions

• Currently: What weather conditions cause contrail-supporting regions?

• Planning stage: Can we predict the occurrence of contrail-supporting regions with sufficient accuracy at timescales required by operational flight planning?

• REACT4C2 ? (depends on results from REACT4C)

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Thank you!

Information from:

e.a.irvine@reading.ac.uk

www.react4c.eu

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