extreme precipitation from extra-tropical cyclones: a limited area model climate change analysis
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Extreme Precipitation from Extra-Tropical Cyclones: A Limited Area Model Climate Change Analysis. Adrian Champion, Kevin Hodges, Lennart Bengtsson NCEO National Centre for Earth Observation University of Reading. Adrian Champion [email protected] EGU, Vienna, 3 rd – 8 th April 2011. - PowerPoint PPT PresentationTRANSCRIPT
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 [email protected], Vienna, 3rd – 8th April 2011
Past Events – November 2009 (Cumbria)
Adrian Champion [email protected], Vienna, 3rd – 8th April 2011
Outline
• Global Climate Model
• Limited Area Model
• Downscaling
• Conclusions
Adrian Champion [email protected], Vienna, 3rd – 8th April 2011
Outline
• Global Climate Model
• Limited Area Model
• Downscaling
• Conclusions
Adrian Champion [email protected], 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 [email protected]
EGU, Vienna, 3rd – 8th April 2011
Outline
• Global Climate Model
• Limited Area Model
• Downscaling
• Conclusions
Adrian Champion [email protected], 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 [email protected]
EGU, Vienna, 3rd – 8th April 2011
Outline
• Global Climate Model
• Limited Area Model
• Downscaling
• Conclusions
Adrian Champion [email protected], 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 [email protected], Vienna, 3rd – 8th April 2011
Outline
• Global Climate Model
• Limited Area Model
• Downscaling
• Conclusions
Adrian Champion [email protected], 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 [email protected]
EGU, Vienna, 3rd – 8th April 2011