imported>Tomdufall: Update information on current Met Office and BoM UM models

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Update information on current Met Office and BoM UM models

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The '''Unified Model''' is a [[numerical weather prediction]] and [[climate modeling]] software suite originally developed by the [[United Kingdom]] [[Met Office]] from 1990<ref>[http://www.metoffice.gov.uk/research/modelling-systems/unified-model/weather-forecasting Use of the Unified model for weather forecasting at the Met Office] The Met Office 2011. Retrieved 10 November 2011.</ref><ref>[http://www.metoffice.gov.uk/research/modelling-systems/unified-model/climate-models Use of the Unified model for climate modeling at the Met Office] The Met Office 2011. Retrieved 10 November 2011.</ref> and now both used and further developed by many weather-forecasting agencies around the world.<ref>[http://www.metoffice.gov.uk/research/collaboration/um-collaboration The Unified Model Collaboration]. The Met Office 2010. Retrieved 22 April 2010.</ref> The Unified Model gets its name because a single model is used across a range of both timescales (nowcasting to centennial) and spatial scales (convective scale to climate system earth modelling).<ref>[http://www.metoffice.gov.uk/research/modelling-systems/unified-model The Unified Model]. The Met Office 2011. Retrieved 10 November 2011.</ref> The models are [[finite difference method|grid-point]] based, rather than [[spectral method|wave based]], and are run on a variety of [[supercomputers]] around the world. The Unified Model atmosphere can be coupled to a number of ocean models.<ref>[http://www.metoffice.gov.uk/research/models/ocean-models Met Office ocean models] The Met Office 2011. Retrieved 10 November 2011.</ref> At the Met Office, it is used for the main suite of weather prediction models, for deployable and on-demand weather models, and for seasonal and climate modelling. Similar Unified Model suites with global and regional domains are used by many other national or military weather agencies around the world for operational forecasting.

Data for numerical weather prediction is provided by observations from satellites, from the ground (both human and from automatic weather stations), from buoys at sea, radar, [[weather balloon|radiosonde weather balloons]], [[wind profiler]]s, commercial aircraft and a background field from previous model runs.
The computer model is only adjusted towards the observations using [[Data assimilation|assimilation]], rather than forcing the model to accept an observed value that might make the system unstable (and could be an inaccurate observation).<ref>[http://www.metoffice.gov.uk/research/weather/data-assimilation-and-ensembles Met Office data assimilation and ensembles]. Retrieved 28 December 2009.</ref>
The Unified Model software suite is written in [[Fortran]] (originally 77 but predominantly 90 {{as of|2003|lc=y}}).<ref name="for_90">{{cite web |url=http://www.metoffice.gov.uk/research/nwp/numerical/fortran90/index.html |archive-url=http://webarchive.nationalarchives.gov.uk/20030430155846/http://www.metoffice.gov.uk/research/nwp/numerical/fortran90/index.html |url-status=dead |archive-date=2003-04-30 |title = Fortran 90 |year=2008 | publisher=The Met Office |access-date=2008-08-30}} </ref>
Because most developments of interest are near to the ground the vertical layers are closer together near the surface.<ref name="vert_layers">{{cite web |url=http://research.metoffice.gov.uk/research/nwp/numerical/operational/index.html |title = 2008 Operational Numerical Weather Prediction suites |year=2008 | publisher=The Met Office |access-date=2008-08-30}}</ref> A major update was deployed in August 2002, called "New Dynamics".<ref name="new dynamics">{{cite web |url=http://research.metoffice.gov.uk/research/nwp/numerical/unified_model/new_dynamics.html |archive-url=http://webarchive.nationalarchives.gov.uk/20100618184311/http://research.metoffice.gov.uk/research/nwp/numerical/unified_model/new_dynamics.html |url-status=dead |archive-date=2010-06-18 |title=New Dynamics |year=2008 |publisher=The Met Office |access-date=2008-09-03 }}</ref>

==Principal UM suites at the Met Office==
The Met Office runs a range of [[Numerical Weather Prediction]] suites using the UM.<ref>[http://www.metoffice.gov.uk/science/creating/daysahead/nwp/um.html Met Office Unified Model]. Met Office 2009. Retrieved 28 December 2009.</ref>

All of the models use varying resolutions of [[topography]] with greater accuracy at higher resolutions. The limiting factor with all models is that for a weather event to be recorded by the model it must be at least three grid points in size. Thus, for a model at 40 km, a weather system must be at least 120 km to be modelled. This means smaller phenomena such as small depressions, smaller hurricanes and large thunderstorms are too small for the model to handle. As the resolution increases, smaller events can be caught; the 1.5 km model for example, is reputedly capable of modelling individual showers.

===Global Ensemble Model (MOGREPS-G)===
MOGREPS-G is an [[Ensemble forecasting|ensemble]] model that runs multiple simulations to reduce the overall average error caused by the inherent uncertainty in the observation and modelling process. The model consists of 18 ensemble members with a 10 km horizontal resolution and 70 vertical levels, forecasting out to 168 hours (7 days) with a model run every 6 hours.<ref name="metoffice"/> The latest two runs can be combined to give a 36-member ensemble.

===UK Ensemble Model (MOGREPS-UK)===
The UK ensemble model consists of 3 ensemble members with a 1.5-4 km horizontal resolution and 70 vertical levels, forecasting out to 120 hours (5 days) with a model run every hour.<ref name="metoffice"/> The latest 6 runs can be combined to give a 18-member ensemble.

===Global Deterministic Model===
Approximately 10 km resolution with 70 vertical levels across the entire global domain.<ref name="metoffice">[http://www.metoffice.gov.uk/research/approach/modelling-systems/unified-model/weather-forecasting Atmospheric numerical model configurations as of 2025]. Met Office 2025.</ref> Forecasts alternate between 60 hour (2.5 day) and 144 hour (6 day) extents. The Global model provides boundary information for the smaller-domain models. The model is kept close to the real atmosphere using [[Data assimilation#4D-Var|hybrid 4D-Var data assimilation]]<ref name="hybrid">[http://www.ecmwf.int/newsevents/meetings/annual_seminar/2011/presentations/Barker.pdf Hybrid variational/ensemble data assimilation] {{Webarchive|url=https://web.archive.org/web/20120316084111/http://www.ecmwf.int/newsevents/meetings/annual_seminar/2011/presentations/Barker.pdf |date=2012-03-16 }}. Met Office 2011.</ref> of observations.

===UK Deterministic Model (UKV)===
1.5-4 km horizontal resolution and 70 vertical levels.<ref name="metoffice"/> The resolution is 1.5 km over the UK and 4 km over surrounding areas.<ref name="moukvd">[http://research.metoffice.gov.uk/research/nwp/publications/mosac/doc-2009-06.pdf Issues with high-resolution NWP], discussing the UKV model, Met Office 2010.</ref><ref name="moamsukvd">[http://ams.confex.com/ams/91Annual/webprogram/Paper177409.html Experiences with a 1.5km version of the Met Office Unified Model for short range forecasting], discussing the UKV model, Met Office 2011.</ref> Forecast lengths vary, with hourly forecasts out to 12 hours, three-hourly forecasts out to 54 hours (2.25 days), and twice-daily forecasts out to 120 hours (5 days.) The model uses boundary conditions from the global deterministic model, sea conditions from the [https://www.metoffice.gov.uk/research/weather/ocean-forecasting/high-resolution-regional-ocean-model AMM15 shelf seas model], and is kept close to observations using [[Data assimilation#4D-Var|4D-Var data assimilation]] hourly.

===North Atlantic and European model (retired)===
The Met Office's North Atlantic and European model (NAE) model had 70 levels with a 12 km resolution.<ref name="metoffice" /> It was run out to 48 hours from start. Because the UK is at a northern latitude the model transposes the model area to an equatorial location so that the grid points give an area that is more square. This reduces the load on the model, allowing it to run more quickly. The model was kept close to the real atmosphere using [[Data assimilation|4D-Var data assimilation]] of observations.

===Euro 4km model (retired) ===
70 Vertical levels, 4.4 km horizontal resolution. Ran out to 120 hours.<ref name="metoffice"/> Now superseded by the UKV in many applications and by the Global Model in others.

===DRMs/CAMs===
Defence Regional Models and Crisis Area Models are models using the same science configuration as the UK model which can be deployed rapidly to support military operations and disaster relief efforts.<ref name="metoffice"/> For example, to support the [[Mobile Met Unit|MMU]] or environmental catastrophes.

===Mountain Wave Models===
This high resolution model provides information on [[lee waves|mountain waves]] for a variety of locations around the UK and other areas of interest to the Met Office.

===Met Office's Global Wave Model===
This models sea waves around the world.

==UM suites outside the Met Office==

Unified Model suites which are similar to those from the Met Office are run by the Australian [[Bureau of Meteorology]], the Australian [[Commonwealth Scientific and Industrial Research Organisation]], the [[South African Weather Service]], the [[Norwegian Meteorological Institute]], the New Zealand [[National Institute of Water and Atmospheric Research]], the (South) [[Korea Meteorological Administration]] and the [[National Centre for Medium Range Weather Forecasting]], a subordinate office of the Indian [[Ministry of Earth Sciences (India)|Ministry of Earth Sciences]].

===Australian Bureau of Meteorology===

The Australian [[Bureau of Meteorology]], have an operational 12.5 km resolution deterministic (ACCESS-G) and 33 km resolution ensemble (ACCESS-GE) global forecasting system utilizing the Unified Model. This global system provides boundary conditions for a number of higher resolution regional systems also using the Unified Model. These include a 1.5 km resolution deterministic (ACCESS-C) and 2.2 km resolution ensemble (ACCESS-CE) model over Australia and a 4km resolution relocatable model (ACCESS-TC.)<ref>http://www.bom.gov.au/australia/charts/about/about_access.shtml About the ACCESS model</ref>

===(South) Korea Meteorological Administration===

The (South) [[Korea Meteorological Administration]] have an operational 10 km resolution global forecasting system utilizing the Unified Model. This global system provides boundary conditions for a 1.5 km resolution local Unified Model [[Numerical Weather Prediction|NWP]] system covering the Korean Peninsula Region.

==UKCA==
United Kingdom Chemistry & Aerosols ([[United Kingdom Chemistry and Aerosols model|UKCA]]) is a sub-model of the UM that deals with trace gas and aerosol chemistry within the model.<ref>[http://www.metoffice.gov.uk/research/collaboration/jwcrp/ukca United Kingdom Chemistry and Aerosol model] developed in a collaboration including the Met Office. Accessed 10 November 2011</ref> This includes calculating the concentrations of climatically relevant gases such as [[methane]] and [[ozone]], as well as the composition and evolution of [[aerosols]]. As with most of the UM, the UKCA was written in a collaboration between the [[UK Met Office]] and UK Academia.

==JULES==
Joint UK Land Environment System is a land surface model that has been developed in a collaboration between the Met Office and other research institutes.<ref>[http://www.metoffice.gov.uk/research/collaboration/jwcrp/jules JULES collaboration]. The Met Office 2011. Accessed 10 November 2011</ref> JULES models the exchange of heat and moisture between the Unified Model atmosphere and the land surface and vegetation. JULES can also be used offline to estimate the impacts of different climate models on the land surface and hydrology.

== References ==
{{reflist}}

==External links==
* [http://www.metoffice.gov.uk/research/collaboration/um-collaboration Unified Model Collaboration webpage] at the Met Office.
* [http://www.metoffice.gov.uk/research/nwp/publications/papers/unified_model Unified Model Papers]
* [https://web.archive.org/web/20080918035729/http://ncas-cms.nerc.ac.uk/content/view/67/26/ Introduction to the UM by NCAS]

{{The Met Office}}
{{Atmospheric, Oceanographic and Climate Models}}

[[Category:Numerical climate and weather models]]
[[Category:Met Office]]
[[Category:Scientific simulation software]]

Unified Model - Revision history

imported>Tomdufall: Update information on current Met Office and BoM UM models