Ensemble perturbations

Seasonal and climate models

These are usually lower resolution than the models used for day to day weather forecasting, and include ocean and sea-ice components coupled to the atmosphere model in order to represent the full coupled climate system. Additional processes associated with atmospheric chemistry and the ecosystem are included in "Earth System" configurations only (due to computational cost).

Seasonal and climate configurations of the Unified Model

Current operational seasonal and climate configurations of the Unified Model are indicated in the table below, with higher horizontal and vertical resolution versions under development.

Configuration Atmosphere Resolution Ocean Resolution Initial Conditions Typical Run Length
Seasonal

85 levels to 85 km

0.83° x 0.55°
(~50 km at mid-latitudes)

75 levels

0.25° x 0.25°

Atmos: Met Office global analyses

Ocean and sea ice (concentrations): data assimilation based on 

42-member ensembles of ~7 month runs, updated monthly
Decadal

85 levels to 85 km

0.83° x 0.55°
(~50 km at mid-latitudes)

75 levels

0.25° x 0.25°

Atmos: ECMWF global analyses

Ocean: data assimilation of observed full fields

10-member ensembles of ~5 year runs, updated annually
Centennial

38 levels to 40 km

1.875° x 1.25°
(~140 km at mid-latitudes)

40 levels

1.0° x (1.0° increasing smoothly from 30°N/S to 0.33° at equator)

Atmos: Met Office global analyses representative of current climate

Ocean: Levitus present-day observed ocean conditions

Sea ice: present-day conditions taken from previous climate model 20th century simulation

~100s years
Earth System

38 levels to 40 km

1.875° x 1.25°
(~140 km at mid-latitudes)

40 levels

1.0° x (1.0° increasing smoothly from 30°N/S to 0.33° at equator)

Atmos: Met Office global analyses representative of current climate

Ocean: Levitus present-day observed ocean conditions

Sea ice: present-day conditions taken from previous climate model 20th century simulation

~100s years

Regional climate

19 levels

0.22° x 0.22° (~24km) to 0.44° x 0.44° (~50km)

Limited area

- Met Office global analyses;
ECMWF reanalyses used at lateral boundaries
~10 years, or up to 150 years for climate change runs

Climate change predictions

Centennial climate predictions from the Met Office Hadley Centre have been included in all of the climate change Assessment Reports of the Intergovernmental Panel on Climate Change. The named climate configurations used in these reports were:

More information on our seasonal and climate models

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