The
Unified Model is the collection of
Numerical Weather PredictionNumerical weather prediction uses current weather conditions as input into mathematical models of the atmosphere to predict the weather. While the first efforts to accomplish this were done in the 1920s, it wasn't until the advent of the computer that it was feasible to do in real-time...
computer models used by the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
Met OfficeThe Met Office , is the United Kingdom's national weather service, and a trading fund of the Ministry of Defence. Part of the Met Office headquarters at Exeter in Devon is the Met Office College, which handles the training for internal personnel and many forecasters from around the world...
. It includes the main suite of a Global Model, a UK and North Atlantic model and a high resolution UK model, in addition to a variety of Crisis Area Models and other models that can be run on demand. The models are grid based, rather than wave based and are run on a variety of supercomputers.
Data are provided by observations (human and automatic), satellites, radar,
radiosonde weather balloonsA weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, and humidity by means of a small, expendable measuring device called a radiosonde...
,
wind profilerA wind profiler is a type of weather observing equipment that uses radar or sound waves to detect the wind speed and direction at various elevations above the ground. Readings are made at each kilometer above sea level, up to the extent of the troposphere...
s and a background field from previous model runs.
The produced data are verified against actual data for initial conditions and the first two hours and problems are worked towards in subsequent model runs, rather than force the model to accept a real value that may make the system unstable.
The models are written in Fortran (originally 77 but working towards 90) and use height as the vertical variable .
Because most developments of interest are at near to the ground the vertical layers are closer together near the surface.
Approximately 40 km resolution (at mid latitudes, 0.5625 x 0.375 degrees) with 50 vertical levels.
The
Unified Model is the collection of
Numerical Weather PredictionNumerical weather prediction uses current weather conditions as input into mathematical models of the atmosphere to predict the weather. While the first efforts to accomplish this were done in the 1920s, it wasn't until the advent of the computer that it was feasible to do in real-time...
computer models used by the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
Met OfficeThe Met Office , is the United Kingdom's national weather service, and a trading fund of the Ministry of Defence. Part of the Met Office headquarters at Exeter in Devon is the Met Office College, which handles the training for internal personnel and many forecasters from around the world...
. It includes the main suite of a Global Model, a UK and North Atlantic model and a high resolution UK model, in addition to a variety of Crisis Area Models and other models that can be run on demand. The models are grid based, rather than wave based and are run on a variety of supercomputers.
Data are provided by observations (human and automatic), satellites, radar,
radiosonde weather balloonsA weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, and humidity by means of a small, expendable measuring device called a radiosonde...
,
wind profilerA wind profiler is a type of weather observing equipment that uses radar or sound waves to detect the wind speed and direction at various elevations above the ground. Readings are made at each kilometer above sea level, up to the extent of the troposphere...
s and a background field from previous model runs.
The produced data are verified against actual data for initial conditions and the first two hours and problems are worked towards in subsequent model runs, rather than force the model to accept a real value that may make the system unstable.
The models are written in Fortran (originally 77 but working towards 90) and use height as the vertical variable .
Because most developments of interest are at near to the ground the vertical layers are closer together near the surface.
Global Model
Approximately 40 km resolution (at mid latitudes, 0.5625 x 0.375 degrees) with 50 vertical levels. Covers the entire globe and 144 hours in the future twice a day. The Global model provides boundary information for the North Atlantic European (NAE) model, for which additional shorter runs (48 hours) are produced twice a day.
North Atlantic and European
The North Atlantic and European model (NAE) has 38 levels with a 12 km resolution. It is run out to 48 hours from start. Because the UK is at a northern latitude the computer transposes the model area to an equatorial location so the grid points give an area that is more square. This reduces the load on the model, allowing it to run more quickly.
UK 4km
38 Vertical levels, 4 km horizontal resolution. Run out to 36 hours.
CAM
The Crisis Area Model is a 12 km model that can be run for any area of the world should the need arise. This can include military use (the MMU use this on deployed operations) or environmental catastrophes.
Mountain Wave Models
This high resolution model provides information on
mountain wavesIn meteorology, lee waves are atmospheric standing waves. The most common form is mountain waves, which are atmospheric internal gravity waves...
for a variety of locations around the UK and other areas of interest to the Met Office.
1.5-4 km variable resolution UKV model
A trial model, not operational at the time of writing. This is run every 3 hours using starting conditions from the 12-km North Atlantic and European (NAE) model. The resolution is 1.5 km over the UK, and 4 km over surrounding areas.
All of the models use varying resolutions of
topographyTopography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
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 the global 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 catch them. As the resolution increases smaller events can be caught, the 1.5 km model for example, is reputedly capable of modelling individual showers.
UKCA
United Kingdom Chemistry & Aerosols (
UKCAUKCA is a community Chemistry-Aerosol-Climate model which is a submodel of the Met Office's Unified Model....
) is a sub-model of the UM that deals with trace gas and aerosol chemistry within the model. This includes calculating the concentrations of climatically relevant gases such as
methaneMethane is a chemical compound with the chemical formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees. Burning methane in the presence of oxygen produces carbon dioxide and water. The relative abundance of methane and its clean...
and
ozoneOzone or trioxygen is a simple triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic O
2. Ground-level ozone is an air pollutant with harmful effects on the respiratory systems of animals...
, 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.
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