extreme precipitation from extra-tropical cyclones: a limited area model climate change analysis

Extreme Precipitation from Extra-Tropical Cyclones:A Limited Area Model Climate Change Analysis

Adrian Champion, Kevin Hodges, Lennart BengtssonNCEO National Centre for Earth Observation

University of Reading

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Past Events – July 2007 (Reading)

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Past Events – November 2009 (Cumbria)

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Past Events – Winter 2009/2010 (UK)

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Outline

• Global Climate Model

• Limited Area Model

• Downscaling

• Conclusions

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Outline

• Global Climate Model

• Limited Area Model

• Downscaling

• Conclusions

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Global Climate Model

• ECHAM 5 GCM T319 & T213– 40km (T319), 60km (T213) resolutions

• TRACK software developed by Hodges (1995,1999)– 850hPa relative vorticity at T42 resolution– 2 day duration, travel 1000 km

• 2 periods:– “20th Century”: 1980-2000 (T319)/1960-1990 (T213)– “21st Century”: 2080-2100/2070-2100 (T213)

• 5° area around centre of storm• Extreme Value Theory used to investigate tails of distributions

– Generalised Pareto Distribution (Peaks-over-Threshold)

Champion, A.J., Hodges, K.I., Bengtsson, L.O., Keenlyside, N., 2011, Tellus A, submittedAdrian Champion a.j.champion@reading.ac.uk

EGU, Vienna, 3rd – 8th April 2011

Global Climate Model

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Global Climate Model

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Global Climate Model

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Outline

• Global Climate Model

• Limited Area Model

• Downscaling

• Conclusions

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Limited Area Model

• UK Met Office’s Unified Model– vn6.1, non-hydrostatic– 12 km & 4 km resolutions– nested vs. makebc– 12W to 10E, 44N to 62N

• ECMWF Operational Analysis initial conditions and boundary conditions

• 4 lead times: 12, 24, 36 and 48 hours before peak precipitation, boundary conditions applied every 6 hours

• Output every hourAdrian Champion a.j.champion@reading.ac.uk

EGU, Vienna, 3rd – 8th April 2011

Limited Area Model

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Limited Area Model

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Limited Area Model

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Outline

• Global Climate Model

• Limited Area Model

• Downscaling

• Conclusions

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Downscaling

• Boundary conditions from ECHAM 5 T213 GCM• Events identified via TRACK

– 6 events: 3 20th century climate, 3 21st century climate– cross the UK– travelling from South-West to North-East

• UK Met Office’s Unified Model– vn6.1, non-hydrostatic– 12 km & 4 km resolutions– nested vs. makebc– 12W to 10E, 44N to 62N– 4 lead times: 12, 24, 36 and 48 hours before peak precipitation

• ~100 km2 area around peak precipitation

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Outline

• Global Climate Model

• Limited Area Model

• Downscaling

• Conclusions

Adrian Champion a.j.champion@reading.ac.ukEGU, Vienna, 3rd – 8th April 2011

Conclusions

• GCM– resolution

• DJF – more extreme events in 21C higher resolution only• JJA – more extreme events at higher resolution (both climates)

– warmer climate• reduction in return periods for a given return level

• LAM– 12 hour lead time produces most intense precipitation– nested/makebc: little difference at 12 hour lead time– raingauges: Met Office and 4km agree, EA don’t

• Downscaling– no preliminary results

www.nerc-essc.ac.uk/~ajcAdrian Champion a.j.champion@reading.ac.uk

EGU, Vienna, 3rd – 8th April 2011