HadCM3-THC HadCM3 Climate Simulation - suppressed thermohaline circulation experiment. Met Office Hadley Centre HadCM3-THC 2007-02-01 Exeter/Devon/UK Met Office Hadley Centre model grid Investigator Data Owner Tim Johns tim.johns@metoffice.gov.uk +44 (0) 1392 886901 +44 (0) 1392 885681 Met Office Hadley Centre Fitzroy Road Exeter Devon EX1 3PB UK Metadata Contact Mark Elkington mark.elkington@metoffice.gov.uk +44 (0) 1392 884835 +44 (0) 1392 885681 Met Office Hadley Centre Fitzroy Road Exeter Devon EX1 3PB UK EARTH SCIENCE Atmosphere Aerosols EARTH SCIENCE Atmosphere Atmospheric Pressure EARTH SCIENCE Atmosphere Energy/Radiation Balance EARTH SCIENCE Atmosphere Atmospheric Temperature EARTH SCIENCE Atmosphere Atmospheric Water Vapour EARTH SCIENCE Atmosphere Atmospheric Winds EARTH SCIENCE Atmosphere Clouds EARTH SCIENCE Atmosphere Precipitation EARTH SCIENCE Cryosphere Frozen Ground EARTH SCIENCE Cryosphere Sea Ice EARTH SCIENCE Cryosphere Snow/Ice EARTH SCIENCE Land Surface Frozen Ground EARTH SCIENCE Land Surface Land Temperature EARTH SCIENCE Land Surface Soils Soil Moisture EARTH SCIENCE Land Surface Soils Soil Temperature EARTH SCIENCE Land Surface Surface Radiative Properties EARTH SCIENCE Oceans Ocean Circulation EARTH SCIENCE Oceans Ocean Heat Budget EARTH SCIENCE Oceans Ocean Pressure EARTH SCIENCE Oceans Ocean Temperature EARTH SCIENCE Oceans Ocean Winds EARTH SCIENCE Oceans Salinity/Density EARTH SCIENCE Oceans Sea Ice EARTH SCIENCE Terrestrial Hydrosphere Ground Water Soil Moisture EARTH SCIENCE Terrestrial Hydrosphere Snow/Ice EARTH SCIENCE Terrestrial Hydrosphere Surface Water Climatology/Meteorology/Atmosphere 2091-12-01 2257-05-01 360 Day Complete 90S 90N 180W 180E 0 km 50 Pa 0 km 5.2 km 2.75 degrees in the atmosphere 3.75 degrees in the atmosphere 250 km - < 500 km or approximately 2.5 deg - < 5.0 deg 19 levels in the atmosphere 30 minutes in atmosphere - typically averaged on day, month, season or year Daily Climatology 1.25 degrees in the ocean 1.25 degrees in the ocean 100 km - < 250 km or approximately 1 deg - < 2.5 deg 10m to 616m (20 levels in the ocean) 10 meters - < 30 meters 1 hour in ocean - typically averaged on day, month, season or year Daily Climatology HadCM3 Hadley Centre Coupled Model Version 3 Registration with the British Atmospheric Data Centre is required before this data set can be accessed.(http://badc.nerc.ac.uk) This dataset must only be used for scientific purposes unless specific authorisation is given by the Met Office. The Met Office must be acknowledged in any reproduction of data, publication of papers, reports, presentations and other literature arising from the use of these data. British English Met Office Hadley Centre GB/NCAS/BADC British Atmospheric Data Centre, NERC Centres for Atmospheric Science, United Kingdom http://badc.nerc.ac.uk/ HadCM3-THC Data Centre Contact BADC Support badc@rl.ac.uk +44 (0) 1235 446432 +44 (0) 1235 446314 Space Science and Technology Department R25 - Room 2.122 Rutherford Appleton Laboratory Chilton, Nr Didcot Oxfordshire OX11 0QX UK online FTP 165Gb PP None (for scientific use) online FTP 165Gb netCDF None (for scientific use) Vellinga, M., R.A. Wood and J.M. Gregory (2002) Processes governing the recovery of a perturbed thermohaline circulation in HadCM3. Journal of Climate, Vol 15, 764-780. Pope, V., M.L. Gallani, P.R. Rowntree, R.A. Stratton, (2000) The impact of new physical parameterisations in the Hadley Centre climate model: HadAM3. Climate Dynamics, 16, pp123-146. Gordon, C., C. Cooper, C.A. Senior, H.T. Banks, J.M. Gregory, T.C. Johns, J.F.B Mitchell and R.A. Wood (2000) The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled moel without flux adjustments. Climate Dynamics, 16, pp147-168. Johns, T.C., J.M. Gregory, W.J. Ingram, C.E. Johnson, A. Jones, J.A. Lowe, J.F.B. Mitchell, D.L. Roberts, D.M.H Sexton, D.S Stevenson, S.F.B. Tett, M.J. Woodage (2003) Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios. Climate Dynamics, 20, 583-612. The Hadley Centre Coupled Model Version 3 was developed from the earlier HadCM2 model. Various improvements were applied to the 19 level atmosphere model and the 20 level ocean model and as a result the model requires no artificial flux adjustments to prevent excessive climate drift. The atmosphere and ocean exchange information once per day, heat and water fluxes being conserved exactly. Momentum fluxes are interpolated between atmosphere and ocean grids so are not conserved precisely, but this non-conservation is not thought to have a significant effect. The main differences from the previous HadCM2 model are a significantly more sophisticated radiation scheme; the inclusion of the direct impact of convection on momentum; and the inclusion of a new land surface scheme that includes a better representation of evaporation, freezing and melting of soil moisture. The HadCM3 model was used by the Hadley Centre to provide input for the IPCC Third Assessment Report. The Thermohaline Circulation simulation dataset was produced to investigate the response of the HadCM3 model to a suppression of the thermohaline circulation in the Atlantic Ocean. The suppression was induced by a strong initial perturbation to the salinity distribution in the upper layer of the northern North Atlantic. The model was then allowed to adjust freely. VIEW EXTENDED METADATA http://www.metoffice.gov.uk/research/link/metadata/HadCM3_THC.xml More detailed metadata on the model configuration and parameters is available in XML format GET DATA http://badc.nerc.ac.uk/ Users must register with the British Atmospheric Data Centre to access this data set. CEOS IDN DIF 9.7 2008-05-01 2008-12-01 2010-12-01 False HadCM3 NumSim www.metoffice.gov.uk LINK GCM The Hadley Centre Hadley Centre Coupled Model Version 3 was developed from the earlier HadCM2 model in the period 1997-2000. Various improvements were applied to the 19 level atmosphere model and the 20 level ocean model and as a result the model requires no artificial flux adjustments to prevent excessive climate drift. The atmosphere and ocean exchange information once per day, heat and water fluxes being conserved exactly. The main differences from the previous HadCM2 model are a significantly more sophisticated radiation scheme; the inclusion of the direct impact of convection on momentum; and the inclusion of a new land surface scheme that includes a better representation of evaporation, freezing and melting of soil moisture. It improved on the resolution available from previous Hadley Centre models and included support for interactive couplings between the atmosphere and ocean and the biosphere, atmospheric chemistry, the sulphur cycle and atmospheric aerosols. The HadCM3 model was used by the Hadley Centre to provide input for the IPCC Third Assessment Report. Pope, V., M.L. Gallani, P.R. Rowntree, R.A. Stratton, (2000) The impact of new physical parameterisations in the Hadley Centre climate model: HadAM3. Climate Dynamics, 16, pp123-146. Gordon, C., C. Cooper, C.A. Senior, H.T. Banks, J.M. Gregory, T.C. Johns, J.F.B Mitchell and R.A. Wood (2000) The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled moel without flux adjustments. Climate Dynamics, 16, pp147-168. Johns, T.C., J.M. Gregory, W.J. Ingram, C.E. Johnson, A. Jones, J.A. Lowe, J.F.B. Mitchell, D.L. Roberts, D.M.H Sexton, D.S Stevenson, S.F.B. Tett, and M.J. Woodage (2003) Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios. Climate Dynamics, 20, 583-612. Atmosphere Atmosphere The atmospheric model component in HadCM3 is a version of the UKMO unified forecast and climate model configured with a horizontal grid spacing of 2.5° x 3.75° and 19 vertical levels using an Arakawa B gird and hybrid vertical co-ordinates. The time step is 30 min. Davies, T., M. J. P. Cullen, A. J. Malcolm, M. H. Mawson, A. Staniforth, A. A. White, and N. Wood, (2005) A new dynamical core for the Met Office’s global and regional modelling of the atmosphere. Quarterly Journal Royal Meteorology Society, 131, 1759–1782. Radiation Scheme RadiationScheme HadCM3 uses the new radiation scheme developed by Edwards and Slingo (1996) and modified by Cusack et al. (1999). This has six shortwave bands and eight longwave bands. As well as including the effects of CO2, H2O, and O3 it also includes the effects of O2, N2O, CH4, CFC11 and CFC12. The model uses trace gas values appropriate for the period 1979-1988. HadCM3 also includes the developments made by Cusack et al. (1998) to include the effects of background aerosols. Further improvements in HadCM3 are that ice crystals and water droplets are treated separately in the radiation scheme. Cloud overlaps are treated consistently in the shortwave and the longwave regions: in particular, layer cloud in the shortwave is no longer reduced to three layers. Edwards, J.M. and A. Slingo (1996) Studies with a flexible new radiation code. I: choosing a configuration for a large-scale model. Quarterly Journal Royal Meteorological Society, 122, 689-719. Cusack, S., J.M. Edward, and J.M. Crowther (1999) Investigating k-distribution methods for parametrizing gaseous absorption in the Hadley Centre climate model. Journal Geophysical Research 104, 2051-2057. Cusack, S., A. Slingo, J.M. Edwards, and M. Wild (1998) The radiative impact of a simple aerosol climatology on the Hadley Centre climate model. Quarterly Journal Royal Meteorological Society, 124, 2517-2526. Aerosols Scheme Aerosol Three modes of sulfate aerosols (Aitken, accumulation and dissolved in cloud droplets) with explicit parameterisations of transfers between the different modes. Sulfur dioxide (SO2) and dimethyl sulfide (DMS) are injected at appropriate levels. The direct radiative effect from scattering and absorption is taken into account. The indirect effect was implemented by prescribing cloud changes claculated using offline models (see Johns et al., 2003). Johns, T.C., J.M. Gregory, W.J. Ingram, C.E. Johnson, A. Jones, J.A. Lowe, J.F.B. Mitchell, D.L. Roberts, D.M.H Sexton, D.S Stevenson, S.F.B. Tett, and M.J. Woodage (2003) Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios. Climate Dynamics, 20, 583-612. Land Surface Scheme LandSurface A new land surface scheme (Cox et al. 1999) includes a representation of the freezing and melting of soil moisture, as well as surface runoff and soil drainage; the formulation of evapotranspiration includes the dependence of stomatal resistance on temperature, vapour pressure and CO2 concentration. The surface albedo is a function of snow depth, vegetation type and also of temperature over snow and ice. Cox, P. M., R. A. Betts, C. B. Bunton, R. L. H. Essery, P. R. Rowntree, and J. Smith, 1999: The impact of new land surface physics on the GCM simulation of climate and climate sensitivity. Climate Dyn., 15, 183–203. Essery, R., M. Best, and P. Cox, 2001: MOSES 2.2 technical documentation. Hadley Centre Technical Note 30, 30 pp. Boundary Layer Scheme Atmosphere In HadCM2, the boundary layer scheme consisted of a local mixing scheme. This uses a mixing coefficient, which is a function of a mixing length, the local wind shear and atmospheric stability. It also includes a representation of non-local mixing ("rapidly mixing scheme"; Smith 1993) which uniformly distributes the heating and moistening resulting from the divergence of the fluxes between the surface and the top of the boundary layer. The rapidly mixing scheme was included because, in unstable regions, the fluxes are in fact not closely related to the local gradients. Also, the local values of stability can be influenced by other parts of the model, particularly the convection scheme, thereby altering the turbulent mixing unrealistically. However, during the development of HadCM3, it was found that the rapidly mixing scheme produced unfavourable interactions with the transport and sink of aerosols. Therefore, the rapidly mixing scheme is switched off in HadCM3. In addition, the mixing length is reduced above the diagnosed top of the boundary layer and increased in the mixed layer. Also, the amount of freezing and melting of convective precipitation which is not falling through downdraughts is limited so that the temperature change due to the phase change does not increase/decrease the temperature above or below the melting point of water. Pope, V., M.L. Gallani, P.R. Rowntree, R.A. Stratton, (2000) The impact of new physical parameterisations in the Hadley Centre climate model: HadAM3. Climate Dynamics, 16, pp123-146. Smith R. N. B (1993) Experience and developments with the layer cloud and boundary layer mixing schemes in the UK Meteorological Office Unified Model. Proc. ECMWF/GCSS Workshop on Parametrization of the Cloud-Topped Boundary Layer, ECMWF, Reading, England, 319–339. Convection Scheme ConvectionScheme The convection scheme in the HadCM3 model was improved by adding a parameterisation of the direct impact of convection on momentum (Gregory et al. 1997). Moist and dry convection are modelled using the mass-flux scheme of Gregory and Rowntree (1990) with the addition of convective downdrafts (Gregory and Allen, 1991). Gregory, D., R. Kershaw, and P. M. Innes (1997) Parametrisationof momentum transport by convection II - tests in single column and general circulation models. Quarterly Journal Royal Meteorological Society 123; 1153-1183. Gregory, J. and P.R. Rowntree (1990) A mass flux convection scheme with representation of cloud ensemble characteristics and stability- dependent closure. Monthly Weather Review, 118, 1483–1506. Gregory, J. and S. Allen (1991) The effect of convective scale downdrafts upon NWP and climate simulations. Ninth Conference on Numerical Weather Prediction. Denver, Colorado. American Meteorological Society pp 122-123. Gravity Wave Scheme GravityWaves A parametrisation of orographic drag (Milton and Wilson 1996) and a new gravity wave drag scheme including anisotropy of orography, high drag states and flow blocking, and trapped lee waves have been included (Gregory et al. 1998). Milton, S.F., and C.A. Wilson (1996) The impact of parameterised sub-grid scale orographic forcing on systematic errors in a global NWL model. Monthly Weather Review, 124, 2023-2045. Gregory, D., G.J Shutts, and J.R. Mitchell (1998) A new gravity wave drag scheme incorporating anisotropic orography and low level wave breaking: impact upon the climate of the UK Meteorological Office Unified Model. Quarterly Journal Royal Meteorological Society, 124, 463-493. Precipitation and Cloud Scheme CloudScheme The HadCM3 model uses a prognostic cloud scheme, described by Smith (1990) and modified by Gregory and Morris (1996), which diagnoses cloud ice, cloud water and cloud amount from the primary model variables, total moisture and liquid water potential temperature. The model uses the precipitation scheme described by Senior and Mitchell (1993) together with the evaporation of precipitation described by Gregory (1995). The partitioning of mixed phase clouds into ice and water has been changed from 0 to -15 °C to 0 to -9 °C (Gregory and Morris 1996) based on evidence from observational data. A parametrisation of the effective radius of cloud droplets as a function of cloud water content and droplet number concentration is also included (Martin et al. 1994). Several parameters in the layer cloud scheme (Smith 1990) have been altered. Cloud cover forms when the standard deviation of the distribution of total water content in a grid box goes above a critical relative humidity which is held at a constant value at each level of the model. In HadCM3 this has been changed from 0.85 to 0.7 to improve the top-of-the-atmosphere (TOA) radiation balance. The equation for liquid precipitation includes a threshold value of the total water content, below which water does not precipitate. The value of this threshold is different over land and ocean to represent the different amounts of cloud condensation nuclei. In HadCM3, these values were reduced from 8 x 10-4 to 2 x 10-4 over land and from 2 x 10-4 to 0.5 x 10-4 over sea. In combination, these changes improved the net TOA radiative ¯uxes when compared with Earth Radiation Budget Experiment (ERBE) data, especially over northern mid-latitude oceans. Smith, R. N. B. (1990) A scheme for predicting layer clouds and their water content in a general circulation model. Quarterly Journal of Royal Meteorological Society, 116, 435–460. Senior C. and Mitchell J. F. B (1993) CO2 and climate: the impact of cloud parametrisation. Journal of Climatology, 6, 393-418. Martin G.M., D.W. Johnson, and A. Spice (1994) The measurement and parametrisation of effective radius of droplets in warm stratocumulus clouds. Journal of Atmospheric Science, 51, 1823-1842. Gregory D. (1995) A consistent treatment of the evaporation of rain and snow for use in large-scale models. Monthly Weather Review, 123, 2716-2732. Gregory D. and D. Morris (1996) The sensitivity of climate simulations to the specification of mixed phase clouds. Climate Dynamics, 12, 641-651. Ocean Ocean The ocean component of HadCM3 has a number of significant modifications from previous versions of this model component. It is a 20 level version of the Cox (1984) model on a 1.25° x 1.25° latitude-longitude grid. There are six ocean grid boxes to each atmosphere model grid box and each high latitude ocean grid box can have partial sea ice cover. The vertical levels are distributed to provide enhanced resolution near to the ocean surface and are the same as those in the previous coarser horizontal resolution version of the model. The topography was taken from the ETOPO5 (1988) 1/12° resolution dataset and interpolated onto the model grid. A simple smoother was applied to remove gridscale noise. It has been shown that the Bryan-Cox type models are highly sensitive to the depth of the various channels along the Greenland-Iceland-Scotland ridge. Many of these channels are sub-gridscale and so three routes (one grid point wide on the velocity grid) through the ridge were 'excavated'. The Denmark Strait and Iceland-Faeroes ridge were reduced to 797.9 m (bottom of level 12), while the Faeroe- Scotland ridge was set to 534.7 m (bottom of model level 11). This leads to a long-term mean outflow of approximately 8.5 Sv in the coupled simulation, compared with the observed outflow of around 5-6 Sv (Dickson and Brown 1994). An island is also placed at the North Pole to avoid the polar singularity in the spherical co-ordinate system. Cox, M. D. (1984) A primitive equation, three dimensional model of the ocean. Ocean Group Technical Report 1, GFDL, Princeton. ETOPO5 (1988) Global 5' x 5' depth and elevation. Technical Report, National Geophysical Data Centre, NOAA, US Department of Commerce, Boulder, USA.. Journal of Computational Physics, 4, 347-376 Dickson, R.R. and J. Brown. (1994) The production of North Atlantic deep water: sources, rates and pathways. Journal of Geophysical Research, 12, 319-341. Filtering Filtering Fourier filtering is used to decrease the effective resolution of the model at latitudes North of 74.5 degrees, to remove spurious short-wavelength waves due to the convergence of meridians caused by the use of a latitude-longitude grid. An artificial Island is also included. Sunlight Penetration RadiationScheme A two band scheme (one more penetrative) from Paulson and Simpson (1977), assuming pure water type 1B with coefficients adjusted. Paulson C. A. and J. J. Simpson (1977) Irradiance Measurements in the Upper Ocean. Journal of Physical Oceanography, 7, 952-956 Barotropic Solution, Momentum Flux and Diffusion Ocean The HadCM3 model uses a standard "rigid-lid" barotropic solution. Convection ConvectionScheme Convective mixing in the HadCM3 model uses the Rahmstorf (1993) full convection scheme. The equation of state is the UNESCO 1981 polynomial approximation. There are limits on the model surface salinity which is not allowed to go outside the range 0 - 40 PSU. Rahmstorf, S. (1993) A fast and complete convection scheme for ocean models. Ocean Modelling, 101, 9-11. Mixed Layer Scheme MixedLayerScheme Horizontal mixing of tracers uses a version of the adiabatic diffusion scheme of Gent and McWilliams (1990) with a variable thickness diffusion parametrization (Wright 1997; Visbeck et al. 1997). There is no explicit horizontal diffusion of tracers. The along-isopycnal diffusivity of tracers is 1000 m2/s and horizontal momentum viscosity varies with latitude between 3000 and 6000 m2/s at the poles and equator respectively. Near-surface vertical mixing is parametrized by a Kraus-Turner mixed layer scheme for tracers (Kraus and Turner 1967), and a K-theory scheme (Pacanowski and Philander 1981) for momentum. Below the upper layers the vertical diffusivity is an increasing function of depth only. Convective adjustment is modified in the region of the Denmark Straits and Iceland–Scotland ridge better to represent down-slope mixing of the overflow water, which is allowed to find its proper level of neutral buoyancy rather than mixing vertically with surrounding water masses. The scheme is based on Roether et al. (1994). Gent P.R., and J.C. McWilliams (1990) Isopycnal mixing in ocean circulation models. Journal Physical Oceanography, 20, 150–155. Wright D.K., (1997) A new eddy mixing parametrization and ocean general circulation model. International WOCE News, 26, 27–29. Visbeck M., J. Marshall, T. Haine, M. Spall (1997) On the specification of eddy transfer coefficients in coarse resolution ocean circulation models. Journal Physical Oceanography, 27, 381–402. Kraus, E. B. and J. S. Turner (1967) A one-dimensional model of the seasonal thermocline, Part II, Tellus, 19, 98-105. Pacanowski R.C., and S.C. Philander (1981) Parametrization of vertical mixing in numerical models of tropical oceans. Journal Physical Oceanography, 11, 1443–1451. Roether W., V.M. Roussenov, and R. Well (1994) A tracer study of the thermohaline circulation of the eastern Mediterranean. In: Malanotte-Rizzoli P, Robinson AR (eds) Ocean processes in climate dynamics: global and Mediterranean example. Kluwer Academic, 371–394. Salinity Control Ocean Salinity at every point is constrained to remain with the limits 0 - 40 PSU. Some isolated basins reach these limits ; keeping them there implies a small non-conservation of water amounting to 0.2mm/year averaged over the ocean. Surface water fluxes are converted to surface salinity fluxes using a constant reference salinity of 35 PSU. Ocean Straits OceanStraitScheme Mediterranean water is partially mixed with Atlantic water across the Strait of Gibraltar as a simple representation of water mass exchange at an overall level of 1 Sv. Similar parameterisation applied to Hudson Bay. Sea Ice Cryosphere The sea ice model, which is the same as that used in HadCM2, uses a simple thermodynamic scheme and contains parametrisa- tions of ice drift and leads (Cattle and Crossley 1995). A parametrisation of ice concentration based on that of Hibler (1979) is included. Ice concentration is not allowed to exceed 0.995 in the Arctic and 0.980 in the Antarctic since completely unbroken ice cover is rarely observed in reality even in pack ice. Ice forms predominantly by freezing in the leads; it melts at the surface during summer and at the base throughout the year. Ice depth can be increased by the formation of `white ice' (Ledley 1985) where the weight of snow forces the ice-snow interface below the water line. The effect of sea ice formation and melt on ocean salinity is accounted for within the model, assuming a constant salinity of 0.6 parts per thousand for sea ice. Sublimation increases ocean salinity, as the salt is assumed to blow into leads, and white ice formation reduces it to account for the salt added in converting snow to ice. Snowfall reduces ocean salinity in leads, and accumulates onto ice, and all rainfall is assumed to reach the ocean through leads. Cattle, H. and J. Crossley (1995) Modelling Arctic climate change. Philosophical Transactions of the Royal Society, London, A352, 201-213. . Hibler, W. D. (1979) A dynamic-thermodynamic sea ice model. Journal of Physical Oceanography, 13, 1093-1104. Ledley, T. S. (1985) Sea Ice: multiyear cycles and white ice. Journal of Geophysical Research, 90, 5676-5686. Sea Ice Dynamics Cryosphere A simple parametrisation of sea ice dynamics based on Bryan (1969) is also included. The windstress is applied to the ocean beneath the ice. The ice thickness, concentration and snow depth are advected using the top layer ocean current, using an upstream advection scheme. Ice rheology is crudely represented by preventing convergence of ice once the ice depth reaches 4 m (Steele et al. 1997). The ice may become deeper than 4 m due to further freezing. Del-squared horizontal diffusion of ice depth is also applied, with a coefficient 2000 m2 s-1. There is no explicit representation of iceberg calving, so a prescribed water flux is returned to the ocean at a rate calibrated to balance the net snowfall accumulation on the ice sheets, geographically distributed within regions where icebergs are found. In order to avoid a global average salinity drift, surface water fluxes are converted to surface salinity fluxes using a constant reference salinity of 35 PSU. Bryan, K. (1969) Climate and the ocean circulation III: The ocean model. Monthly Weather Review, 97, 806-827. Steele, M., J. Zhang, D. Rothrock, and H. Stern (1997) The force balance of sea ice in a numerical model of the Arctic Ocean. Journal of Geophysical Research, 102, 21 061 - 21 079. Sea Ice Thermodynamics Cryosphere The thermodynamics of the sea-ice model is based on the zero-layer model of Semtner (1976). Surface fluxes over the ice and leads fractions of each grid box, and surface temperatures, are calculated separately within the atmosphere component of the model, assuming a linear temperature profile in the ice. A windmixing energy, used in the mixed layer model, is calculated using the drag coefficient appropriate for leads and weighted by the leads fraction of the grid square. Oceanic heat flux into the base of the ice is related to the temperature difference between the ocean top level and the base of the ice (assumed to be at freezing point of -1.8 °C) with a coupling coefficient of 20 Wm-2 K-1. Semtner, A. (1976) A model for the thermodynamic growth of sea ice in numerical investigations of climate. Journal of Physical Oceanography, 6, 379-389 Sea Ice Albedo Cryosphere The surface albedo is 0.8 at -10 °C and below, and between -10 and 0 °C it falls linearly to 0.5. This parametrisation aims to reproduce some of the effect of the ageing of snow, the formation of melt ponds, and the relatively low albedo of bare ice. events. Atmosphere to Ocean Coupler Coupler The models are coupled once per day. The atmospheric model is run with fixed SSTs through the day and the various forcing fluxes are accumulated each atmospheric model time step. At the end of the day these fluxes are passed to the ocean model which is then integrated forwards in time. The updated SSTs and sea ice extents are then passed back to the atmospheric model. As there are six ocean grid points to every atmospheric grid point interpolation and/or averaging is used to transfer fields between the two grids conserved. River outflow is also included allowing ocean salinity feedbacks via changes over land. Runoff is converted into river outflow using river catchments over land and associated coastal outflow points are defined relative to the model grid. River transport is not modelled explicitly, so runoff is transported instantaneously to the coast. Gordon, C., C. Cooper, C.A. Senior, H.T. Banks, J.M. Gregory, T.C. Johns, J.F.B Mitchell and R.A. Wood (2000) The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Climate Dynamics, 16, pp147-168. HadCM3 Climate Simulation - suppressed thermohaline circulation experiment. NumSim www.metoffice.gov.uk LINK HadCM3 configuration of the Unified Model Version 4.5 The Thermohaline Circulation simulation data contained in this dataset were used to investigate the response of HadCM3 to a significant increase in the freshwater influx to the ocean thus weaking the thermohaline circulation. Vellinga, M., R.A. Wood and J.M. Gregory (2002) Processes governing the recovery of a perturbed thermohaline circulation in HadCM3. Journal of Climate, Vol 15, 764-780. Fixed forcing representative of late nineteenth century conditions as per the HadCM3 control run. Vellinga, M., R.A. Wood and J.M. Gregory (2002) Processes governing the recovery of a perturbed thermohaline circulation in HadCM3. Journal of Climate, Vol 15, 764-780. Johns, T.C., J.M. Gregory, W.J. Ingram, C.E. Johnson, A. Jones, J.A. Lowe, J.F.B. Mitchell, D.L. Roberts, D.M.H Sexton, D.S Stevenson, S.F.B. Tett, M.J. Woodage (2003) Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios. Climate Dynamics, pp583-612. The model was initialised using the conditions from 1991 of the HadCM3 control run. These conditions were perturbed by producing a weakened thermohaline circulation in the model. This was achieved by replacing the salinity field in the top 800m of the northern North Atlantic [(50-90 degrees N) x (80 degrees W to 20 degrees E)] with a vertical profile that is much fresher and has a deeper pycnocline. On average the water in the area of the perturbation is made 2 PSU fresher. Assuming a reference salinity of 35 PSU, the area would have to receive a freshwater pulse of about 16 Sv yr to experience this freshening. Conservation of salt was assured by globally redistributing the salt taken out of the North Atlantic, increasing salinity everywhere by about 0.01 PSU. The model was allowed to adjust freely to the new salinity field. Vellinga, M., R.A. Wood and J.M. Gregory (2002) Processes governing the recovery of a perturbed thermohaline circulation in HadCM3. Journal of Climate, Vol 15, 764-780. UM Runid 2091-12-01T00:00:00 2257-05-01T00:00:00 2091-12-01T00:00:00 2241-12-01T00:00:00 2091-12-01T00:00:00 2091-12-01T00:00:00 SURFACE TEMPERATURE AFTER TIMESTEP 0 01:00:024 SURFACE ZONAL CURRENT AFTER TIMESTEP 0 01:00:028 SURFACE MERID CURRENT AFTER TIMESTEP 0 01:00:029 FRAC OF SEA ICE IN SEA AFTER TSTEP 0 01:00:031 SEA ICE DEPTH (MEAN OVER ICE) M 0 01:00:032 GEOPOTENTIAL HEIGHT: PRESSURE LEVELS 0 01:16:202 TEMPERATURE ON PRESSURE LEVELS 0 01:16:203 RELATIVE HUMIDITY WRT ICE ON P LVS 0 01:16:204 PRESSURE AT MEAN SEA LEVEL 0 01:16:222 U COMPNT OF WIND AFTER TIMESTEP 128 01:00:002 V COMPNT OF WIND AFTER TIMESTEP 128 01:00:003 THETA AFTER TIMESTEP 128 01:00:004 SPECIFIC HUMIDITY AFTER TIMESTEP 128 01:00:010 CONV CLOUD AMOUNT AFTER TIMESTEP 128 01:00:013 CONV CLOUD LIQUID WATER PATH 128 01:00:016 SNOW AMOUNT OVER LAND AFT TSTP KG/M2 128 01:00:023 SURFACE TEMPERATURE AFTER TIMESTEP 128 01:00:024 BOUNDARY LAYER DEPTH AFTER TIMESTEP 128 01:00:025 FRAC OF SEA ICE IN SEA AFTER TSTEP 128 01:00:031 SEA ICE DEPTH (MEAN OVER ICE) M 128 01:00:032 POTENTIAL TEMPERATURE (OCEAN) DEG.C 128 02:00:101 SALINITY (OCEAN) (PSU-35)/1000 128 02:00:102 BAROCLINIC U_VELOCITY (OCEAN) CM/S 128 02:00:121 BAROCLINIC V_VELOCITY (OCEAN) CM/S 128 02:00:122 STREAMFUNCTION (OCEAN) CM3/S 128 02:00:130 STREAMFN TENDENCY (OCEAN) CM3/S/TS 128 02:00:132 MIXED LAYER DEPTH (OCEAN) M 128 02:00:137 HSNOW: AGGREGATE LOCAL SNOW DEPTH M 128 02:00:141 GBM CARYHEAT MISC HEAT FLX(ICE) W/M2 128 02:00:142 GBM HEAT FLUX:OCEAN TO ICE(OCN) W/M2 128 02:00:143 RATE OF SALINITY CHANGE (ICE) PSU/S 128 02:00:144 AICE: AGGREGATE ICE CONCENTRATION 128 02:00:146 HICE: AGGREGATE GBM ICE DEPTH M 128 02:00:147 TAUX: X_WINDSTRESS N/M2 A 128 02:00:150 TAUY: Y_WINDSTRESS N/M2 A 128 02:00:151 WME: WIND MIXING ENERGY FLUX W/M2 A 128 02:00:152 SOL: PEN.SOLAR*LF INTO OCEAN W/M2 A 128 02:00:161 HTN:NONPEN.HT.FLX*LF INTO OCN W/M2 A 128 02:00:162 PLE:PRECIP-EVAP INTO OCEAN KG/M2/S A 128 02:00:165 RIVER OUTFLOW INTO OCEAN KG/M2/S A 128 02:00:166 SNOWFALL INTO OCN/ONTO ICE KG/M2/S A 128 02:00:171 SUBLIMATION FROM SEAICE KG/M2/S A 128 02:00:172 P-E FLUX CORRECTION KG/M2/S A 128 02:00:186 TOPMELT: GBM SEAICE HEAT FLUX W/M2 A 128 02:00:190 BOTMELT: GBM SEAICE HEAT FLUX W/M2 A 128 02:00:191 THICKNESS DIFF COEFF (OCEAN) CM2/S 128 02:00:194 NET DOWN SURFACE SW FLUX: SW TS ONLY 128 01:01:201 NET DN SW RAD FLUX:OPEN SEA:SEA MEAN 128 01:01:203 NET DOWN SURFACE SW FLUX BELOW 690NM 128 01:01:204 INCOMING SW RAD FLUX (TOA): ALL TSS 128 01:01:207 OUTGOING SW RAD FLUX (TOA) 128 01:01:208 CLEAR-SKY (II) UPWARD SW FLUX (TOA) 128 01:01:209 CLEAR-SKY (II) DOWN SURFACE SW FLUX 128 01:01:210 CLEAR-SKY (II) UP SURFACE SW FLUX 128 01:01:211 SW HEATING RATES: ALL TIMESTEPS 128 01:01:232 CLEAR-SKY SW HEATING RATES 128 01:01:233 TOTAL DOWNWARD SURFACE SW FLUX 128 01:01:235 NET DOWNWARD SW FLUX AT THE TROP. 128 01:01:237 UPWARD SW FLUX AT THE TROP. 128 01:01:238 NET DOWN SURFACE LW RAD FLUX 128 01:02:201 NET DN LW RAD FLUX:OPEN SEA:SEA MEAN 128 01:02:203 TOTAL CLOUD AMOUNT IN LW RADIATION 128 01:02:204 OUTGOING LW RAD FLUX (TOA) 128 01:02:205 CLEAR-SKY (II) UPWARD LW FLUX (TOA) 128 01:02:206 DOWNWARD LW RAD FLUX: SURFACE 128 01:02:207 CLEAR-SKY (II) DOWN SURFACE LW FLUX 128 01:02:208 LW HEATING RATES 128 01:02:232 CLEAR-SKY LW HEATING RATES 128 01:02:233 NET DOWNWARD LW FLUX AT THE TROP. 128 01:02:237 TOTAL DOWNWARD LW FLUX AT THE TROP. 128 01:02:238 OZONE MASS MIXING RATIO AFTER LW 128 01:02:260 HT FLUX THROUGH SEAICE:SEA MEAN W/M2 128 01:03:201 HT FLUX FROM SURF TO DEEP SOIL LEV 1 128 01:03:202 SURFACE HEAT FLUX W/M2 128 01:03:217 X-COMP OF SURF & BL WIND STRESS N/M2 128 01:03:219 Y-COMP OF SURF & BL WIND STRESS N/M2 128 01:03:220 SURFACE TOTAL MOISTURE FLUX KG/M2/S 128 01:03:223 WIND MIX EN'GY FL TO SEA:SEA MN W/M2 128 01:03:224 10 METRE WIND U-COMP B GRID 128 01:03:225 10 METRE WIND V-COMP B GRID 128 01:03:226 SFC SH FLX FROM OPEN SEA:SEA MN W/M2 128 01:03:228 EVAP FROM OPEN SEA: SEA MEAN KG/M2/S 128 01:03:232 SURFACE LATENT HEAT FLUX W/M2 128 01:03:234 SEAICE TOP MELT LH FLX:SEA MEAN W/M2 128 01:03:235 TEMPERATURE AT 1.5M 128 01:03:236 SPECIFIC HUMIDITY AT 1.5M 128 01:03:237 DEEP SOIL TEMPERATURE AFTER B.LAYER 128 01:03:238 RELATIVE HUMIDITY AT 1.5M 128 01:03:245 SURFACE SNOWMELT HEAT FLUX W/M2 128 01:03:258 CANOPY CONDUCTANCE M/S 128 01:03:259 GROSS PRIMARY PRODUCTIVITY KG C/M2/S 128 01:03:261 NET PRIMARY PRODUCTIVITY KG C/M2/S 128 01:03:262 PLANT RESPIRATION KG/M2/S 128 01:03:263 EVAP FROM SOIL SURF : RATE KG/M2/S 128 01:03:296 EVAP FROM CANOPY : RATE KG/M2/S 128 01:03:297 SUBLIM. SURFACE (GBM) : RATE KG/M2/S 128 01:03:298 LARGE SCALE RAINFALL RATE KG/M2/S 128 01:04:203 LARGE SCALE SNOWFALL RATE KG/M2/S 128 01:04:204 CONVECTIVE RAINFALL RATE KG/M2/S 128 01:05:205 CONVECTIVE SNOWFALL RATE KG/M2/S 128 01:05:206 CONV. CLOUD AMOUNT ON EACH MODEL LEV 128 01:05:212 TOTAL RAINFALL RATE: LS+CONV KG/M2/S 128 01:05:214 TOTAL SNOWFALL RATE: LS+CONV KG/M2/S 128 01:05:215 TOTAL PRECIPITATION RATE KG/M2/S 128 01:05:216 X COMPONENT OF GRAVITY WAVE STRESS 128 01:06:201 Y COMPONENT OF GRAVITY WAVE STRESS 128 01:06:202 LAND SNOW MELT HEAT FLUX W/M2 128 01:08:202 SOIL MOISTURE CONTENT 128 01:08:208 CANOPY WATER CONTENT 128 01:08:209 SOIL MOISTURE CONTENT IN A LAYER 128 01:08:223 UNFROZEN SOIL MOISTURE FRACTION 128 01:08:229 FROZEN SOIL MOISTURE FRACTION 128 01:08:230 CANOPY THROUGHFALL RATE KG/M2/S 128 01:08:233 SURFACE RUNOFF RATE KG/M2/S 128 01:08:234 SUB-SURFACE RUNOFF RATE KG/M2/S 128 01:08:235 BULK CLOUD AMOUNT AFTER MAIN CLOUD 128 01:09:201 CLOUD LIQUID WATER AFTER MAIN CLOUD 128 01:09:206 CLOUD ICE CONTENT AFTER DYNAM CLOUD 128 01:09:207 ATMOS ENERGY CORR'N IN COLUMN W/M2 128 01:14:201 U WIND ON PRESSURE LEVELS B GRID 128 01:15:201 V WIND ON PRESSURE LEVELS B GRID 128 01:15:202 GEOPOTENTIAL HEIGHT: PRESSURE LEVELS 128 01:16:202 TEMPERATURE ON PRESSURE LEVELS 128 01:16:203 RELATIVE HUMIDITY WRT ICE ON P LVS 128 01:16:204 PRESSURE AT MEAN SEA LEVEL 128 01:16:222 VERT.VEL. ON OCEAN HALF LEVELS CM/S 128 02:30:201 GBM HTN INTO OCEAN BUDGET W/M**2 128 02:30:206 SNOWRATE WHERE NO ICE KG M**-2 S**-1 128 02:30:207 CARYHEAT AFTER ROW CALCULATION W/M2 128 02:30:208 MEAD DIAGNOSTICS: TEMPERATURE W 128 02:30:211 MEAD DIAGNOSTICS: SALINITY KG/S 128 02:30:212 BAROCLINIC X-ACCN (ZUN) CM/S**2 128 02:30:246 BAROCLINIC Y-ACCN (ZVN) CM/S**2 128 02:30:247 ANOM. HEAT "SINK" AT OCN FLOOR W/M2 128 02:30:279 WATER_FLUX*SALINITY/DENSITY m Gs**-1 128 02:30:280 GM EDDY U VELOCITY (OCEAN) 128 02:30:281 GM EDDY V VELOCITY (N FACE) (OCEAN) 128 02:30:282 GM EDDY W VEL (TOP FACE) (OCEAN) 128 02:30:283 TOTAL OCEAN U-VELOCITY CM S**-1 128 02:30:320 TOTAL OCEAN V-VELOCITY CM S**-1 128 02:30:321 AICE INC. DUE TO ADVECTION FRACT/TS 128 02:32:201 HICE INC. DUE TO ADV (& DIFF) M/TS 128 02:32:202 GBM SNOWDEPTH INC ADVECTION M/TS 128 02:32:203 HICE INC. DUE TO DIFFUSION M/TS 128 02:32:204 U COMPONENT OF ICE VELOCITY (M.S-1) 128 02:32:209 V COMPONENT OF ICE VELOCITY (M.S-1) 128 02:32:210 AICE INC. (THERMODYNAMIC) FRACT/TS 128 02:32:211 HICE INC. (THERMODYNAMIC) M/TS 128 02:32:212 GBM SNOWDEPTH THERMODYNAMIC INC M/TS 128 02:32:213 GBM HTN INTO ICE BUDGET W/M**2 128 02:32:214 SNOWRATE WHERE ICY KG M**-2 S**-1 128 02:32:215 GBM HTN INTO OCN WHERE ICY W/M**2 128 02:32:217 GBM SNOWDEPTH ON SEA-ICE M 128 02:32:218 SURFACE HEAT FLUX W/M2 192 01:03:217 X-COMP OF SURF & BL WIND STRESS N/M2 192 01:03:219 Y-COMP OF SURF & BL WIND STRESS N/M2 192 01:03:220 SURFACE TOTAL MOISTURE FLUX KG/M2/S 192 01:03:223 SPECIFIC HUMIDITY AFTER TIMESTEP 2176 01:00:010 CLOUD LIQUID WATER AFTER MAIN CLOUD 2176 01:09:206 CLOUD ICE CONTENT AFTER DYNAM CLOUD 2176 01:09:207 Indicator of local q diffusion 2176 01:13:201 TEMPERATURE AT 1.5M 4096 01:03:236 TEMPERATURE AT 1.5M 8192 01:03:236 BADC 2007-02-01 PP Network 99 Data Extraction Completed 2008-02-01T00:00:00 Data Transfer Completed 2008-02-01T00:00:00 Closed: Request Fulfilled