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Global prediction:Dynamical Seasonal forecasting system : GloSea
• Enhanced version of the Hadley Centre Climate model HadCM3• AGCM: 2.5° x 3.75° x 19L• OGCM: (1.25° to 0.3°) x 1.25° x 40L
• 41-member ocean-atmosphere global forecast ensemble• run to 6 months ahead from initial conditions on 1st of each month• 5 ocean analyses from perturbed wind stresses• Ocean analyses further perturbed with instantaneous SST perturbations• hindcast (‘BACKRUN’) period, 1987-present (1987-2001 calibration)• run at ECMWF as part of developing European multi-model – EURO-SIP
A two in three chance of a colder-than-average winter for much of Europe. If this holds true, parts of the UK – especially southern regions – are expected to have temperatures below normal
There is also an indication for a drier-than-average winter over much of the UK.
Observed temperature anomalies DJF 2005/6
Customers:
• public
• government (Cabinet office)
• planners in utilities, transport, finance & insurance, defence, aviation, local authorities
• biggest ‘story’ ever run by Met Office press office
The statistical forecast suggested colder than average winter (it was supported by the experimental decadal forecast system).
GloSea September and October forecasts suggested cold conditions over Europe.
GloSea forecast the SST tripole and geopotential height patterns consistent with a negative NAO situation – but the signal is weak ~ 40% of observed amplitude (as expected).
Real time analysis of sub-surface ocean temperatures supported the re-emergence of tripole SST anomalies in winter. This was closely (weekly) monitored to see if the forecast was ‘on track’.
Expert interpretation (by research and forecast staff) was used to draw all this together into the headline forecast and to subsequently decide if the forecast should be revised.
Advice was favourably received by UK government – raised profile of SF Met Office now contracted for routine ‘operational’ seasonal forecast briefings
to Cabinet Office …and to Environment Agency re drought in SE UK. transfer of ‘operational’ tasks from Research to Operations Centre
Need ‘pull-through’ of existing understanding to improve CGCMs new post focused on improving European skill, also NERC knowledge transfer
post ENSEMBLES project comparison of decadal and seasonal models
Improve communication being developed for next winter ‘how cold is cold?’ based on feedback (in part from April RMS meeting) issue more detailed probability information avoid confusion caused by displaying component forecasts on the website
(NAO and GloSea output) ‘consolidated’ forecast maps (combining forecasts)
Hindcasts do not give full skill picture – need to know how the models perform under different modes of forcing
this impacts on model calibration/combining strategies Need ways of accounting for climate trend in the preparation and