Why was Winter 2009/10 so cold? Mike Blackburn National Centre for Atmospheric Science, University of Reading With input from Chris Bell, Thomas Toniazzo, Tim Woollings (NCAS; University of Reading); Brian Hoskins (Grantham Institute, Imperial College) Thomas Jung, Laura Ferranti, Frederic Vitart (ECMWF) Royal Meteorological Society, 5 February 2011
Why was Winter 2009/10 so cold?. Mike Blackburn National Centre for Atmospheric Science, University of Reading With input from Chris Bell, Thomas Toniazzo, Tim Woollings (NCAS; University of Reading); Brian Hoskins ( Grantham Institute, Imperial College) - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Why was Winter 2009/10 so cold?
Mike Blackburn
National Centre for Atmospheric Science, University of Reading
With input from
Chris Bell, Thomas Toniazzo, Tim Woollings (NCAS; University of Reading);
Brian Hoskins (Grantham Institute, Imperial College)
Thomas Jung, Laura Ferranti, Frederic Vitart (ECMWF)
Royal Meteorological Society, 5 February 2011
Summary of observed anomalies
• UK global
• Circulation patterns
NAO & blocking
• The phenomena
• Remote influences
Predictability – forecasts
Early winter 2010/11 – comparison
Attribution studies
Outline
Reading, 6 January 2010
Winter 20009/10 in the UK DJF averages
Reading: Tmax, Tmin DJF 0910
Temperature
• Mean 1.6°C
• 2.0°C below 1971-2000 average
Precipitation (%)
• Total 249mm
• 75% of average
Mike Stroud
European anomalies - DJF
NOAA Climate Prediction Center
Temperature Precipitation (% normal)
Surface air temperatureDecember 2009 January 2010 February 2010
DJF average
• Persistence
• Warm Arctic + sub-tropics
NOAA ESRL
Cold mid-latitudes, amid global warmth
NASA Goddard Institute for Space Studies – Hansen et al (2010)
Annual temperature anomalies relative to 1951-1980
Monthly comparison, 2010 vs. previous years
• DJF 2010 global average Ts second warmest on record to 2007
• Contribution from El Niño
“Global temperature is rising as fast in the past decade as in the prior two decades, despite year-to-year fluctuations associated with the El Niño-La Niña cycle of tropical ocean temperature”, Hansen et al (2010)
Downward influence on troposphere (Northern Annular Mode, NAM)
Potential interaction with tropical winds (QBO)(Gray et al (2001)
Solar activity – mechanism 2
Haigh et al (2005), Simpson et al (2009)
Idealised model response to lower stratospheric heating
Feedback between winds and weather systems in the storm-track
5K0K
Equatorial heating
Zonal wind climatology
Zonal wind response
Cold equatorial stratosphere in winter 2009/10 (solar-min + QBO?)
Temperature anomaly DJF 2009/10
Did we expect a disturbed stratospheric vortex in winter 2009/10?
DJF 09/10
QBO – equatorial winds
Modified mean state:
• Solar minimum (Labitzke & Van Loon 1988; Kodera and Kuroda 2002)
• QBO East (Holton & Tan 1980)
• Trend (stronger Brewer-Dobson circulation) (Charlton et al 2008; Bell et al 2010)
…all fit weaker than average polar vortex
Met Office analyses, University of Reading Labitzke and Kunze (2010, JGR)
QBO- east
30hP
a he
ight
, Nor
th P
ole
Did we expect a disturbed stratospheric vortex in winter 2009/10?
Increased planetary wave activity
• El Niño (Ineson and Scaife, 2009; Bell et al 2009)
• Blocking (Martius et al 2010)
• 25 of 27 SSWs in the period 1958-2001 were preceded by blocking
• SSW type is related to blocking location
Blocking frequency preceding stratospheric sudden warming (SSW) events, 1958-2001
Key features of stratospheric flow:• Minor warming – early December• Strong vortex until mid-January – major stratospheric sudden warming (SSW)• Weak, disturbed vortex late winter – persistent easterlies over polar cap
North Pole temperature at 10hPa Zonal wind at 60N 10hPa
Courtesy Andrew Charlton-Perez http://www.met.reading.ac.uk/research/stratclim/current/