The Met Office Unified Model Global Atmosphere 7.0/7.1 and JULES Global Land 7.0 configurations

Walters, David; Baran, Anthony J.; Boutle, Ian; Brooks, M. E.; Earnshaw, Paul; Edwards, John M.; Furtado, Kalli; Hill, Peter; Lock, A. P.; Manners, James; Morcrette, C. J.; Mulcahy, Jane; Sánchez, Claudio; Smith, Chris; Stratton, Rachel; Tennant, Warren; Tomassini, Lorenzo; Weverberg, Kwinten Van; Vosper, Simon; Willett, Martin; Browse, Jo; Bushell, Andrew C.; Carslaw, K. S.; Dalvi, Mohit; Essery, Richard; Gedney, Nicola; Hardiman, Steven C.; Johnson, Ben; Johnson, C. E.; Jones, Andy; Jones, Colin; Mann, Graham; Milton, Sean; Rumbold, Heather; Sellar, Alistair; Ujiie, Masashi; Whitall, Michael; Williams, Keith D.; Zerroukat, M.

doi:10.5194/gmd-12-1909-2019

Cited by 424 publications

(348 citation statements)

References 224 publications

Supporting

Mentioning

343

Contrasting

Order By: Relevance

“…Given the realistic simulation of aerosols in the GA7 model (Walters et al, ) and the apparent large contribution of ACI α to the total aerosol ERF (see section ) our investigation focuses on missing or poorly represented processes that could lead to an excessively large negative aerosol ERF, in particular, parameterizations underpinning the aerosol‐cloud‐radiation interactions. Table outlines all the model experiments carried out in this section.…”

Section: Model Developmentsmentioning

confidence: 99%

“…The activation of aerosol particles to cloud droplets is strongly related to the subgrid vertical velocity variance, σ w , as well as the physical and chemical composition of the aerosols themselves. In GA7, σ w is diagnosed in UKCA‐Activate (West et al, ) as follows:

σ_{w} = \max ((), \sqrt{\frac{2}{3} {TKE}_{BL}}, σ_{w}^{\min}),

where the boundary layer turbulent kinetic energy (TKE BL ) is estimated from the model turbulent mixing scheme as follows:

{TKE}_{BL} = \frac{K_{m}}{τ_{turb}},

where K m is the eddy diffusivity for momentum and τ turb a parameterized turbulent time scale (Walters et al, ). The

σ_{w}^{\min}

is a prescribed minimum value, set to 0.1 m/s in GA7.…”

Section: Model Developmentsmentioning

confidence: 99%

“…Both of these parameters are described in Walters et al () and are tuned only within their estimated uncertainty. In both cases the parameters above are retuned back to the values recommended by the original literature describing the relevant model developments (Furtado et al, ; Grant & Lock, ) and brings the PI net TOA radiation balance to within the target range of 0±0.5 W/m 2 .…”

Section: Defining the Ga71 Configurationmentioning

confidence: 99%

“…This weaker aerosol ERF leads to a total anthropogenic ERF that is positive with a global mean value of +0.75 W/m 2 and thereby satisfies the requirement for acceptance for use in both UKESM and wider CMIP6 simulations with the HadGEM3‐GC3.1 physical model. Below we evaluate the PD performance of the GA7.1 configuration relative to its parent GA7 reported by Walters et al ().…”

Section: Defining the Ga71 Configurationmentioning

confidence: 99%

“…By implementing or improving such processes we examine their impacts on the aerosol ERF in section . Section evaluates the impact of these model changes on the present‐day (PD) climate where we apply the additional criterion that they do not degrade the good performance of GA7 as described in Walters et al (). Our overall aim is to develop an improved physical and Earth system model built solidly on GA7 that is suitable for use in CMIP6.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

Mulcahy

Jones

Sellar

et al. 2018

J Adv Model Earth Syst

Self Cite

150

211

View full text Add to dashboard Cite

Aerosol processes and, in particular, aerosol‐cloud interactions cut across the traditional physical‐Earth system boundary of coupled Earth system models and remain one of the key uncertainties in estimating anthropogenic radiative forcing of climate. Here we calculate the historical aerosol effective radiative forcing (ERF) in the HadGEM3‐GA7 climate model in order to assess the suitability of this model for inclusion in the UK Earth system model, UKESM1. The aerosol ERF, calculated for the year 2000 relative to 1850, is large and negative in the standard GA7 model leading to an unrealistic negative total anthropogenic forcing over the twentieth century. We show how underlying assumptions and missing processes in both the physical model and aerosol parameterizations lead to this large aerosol ERF. A number of model improvements are investigated to assess their impact on the aerosol ERF. These include an improved representation of cloud droplet spectral dispersion, updates to the aerosol activation scheme, and black carbon optical properties. One of the largest contributors to the aerosol forcing uncertainty is insufficient knowledge of the preindustrial aerosol climate. We evaluate the contribution of uncertainties in the natural marine emissions of dimethyl sulfide and organic aerosol to the ERF. The combination of model improvements derived from these studies weakens the aerosol ERF by up to 50% of the original value and leads to a total anthropogenic historical forcing more in line with assessed values.

show abstract

Section: Model Developmentsmentioning

confidence: 99%

σ_{w} = \max ((), \sqrt{\frac{2}{3} {TKE}_{BL}}, σ_{w}^{\min}),

where the boundary layer turbulent kinetic energy (TKE BL ) is estimated from the model turbulent mixing scheme as follows:

{TKE}_{BL} = \frac{K_{m}}{τ_{turb}},

where K m is the eddy diffusivity for momentum and τ turb a parameterized turbulent time scale (Walters et al, ). The

σ_{w}^{\min}

is a prescribed minimum value, set to 0.1 m/s in GA7.…”

Section: Model Developmentsmentioning

confidence: 99%

Section: Defining the Ga71 Configurationmentioning

confidence: 99%

Section: Defining the Ga71 Configurationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

Mulcahy

Jones

Sellar

et al. 2018

J Adv Model Earth Syst

Self Cite

150

211

View full text Add to dashboard Cite

show abstract

The Met Office Global Coupled Model 3.0 and 3.1 (GC3.0 and GC3.1) Configurations

Williams

Copsey

Blockley

et al. 2018

J Adv Model Earth Syst

381

347

View full text Add to dashboard Cite

The Global Coupled 3 (GC3) configuration of the Met Office Unified Model is presented. Among other applications, GC3 is the basis of the United Kingdom's submission to the Coupled Model Intercomparison Project 6 (CMIP6). This paper documents the model components that make up the configuration (although the scientific descriptions of these components are in companion papers) and details the coupling between them. The performance of GC3 is assessed in terms of mean biases and variability in long climate simulations using present‐day forcing. The suitability of the configuration for predictability on shorter time scales (weather and seasonal forecasting) is also briefly discussed. The performance of GC3 is compared against GC2, the previous Met Office coupled model configuration, and against an older configuration (HadGEM2‐AO) which was the submission to CMIP5. In many respects, the performance of GC3 is comparable with GC2, however, there is a notable improvement in the Southern Ocean warm sea surface temperature bias which has been reduced by 75%, and there are improvements in cloud amount and some aspects of tropical variability. Relative to HadGEM2‐AO, many aspects of the present‐day climate are improved in GC3 including tropospheric and stratospheric temperature structure, most aspects of tropical and extratropical variability and top‐of‐atmosphere and surface fluxes. A number of outstanding errors are identified including a residual asymmetric sea surface temperature bias (cool northern hemisphere, warm Southern Ocean), an overly strong global hydrological cycle and insufficient European blocking.

show abstract

Cloud Condensate and Radiative Feedbacks at Midlatitudes in an Aquaplanet

Bodas‐Salcedo

2018

Geophysical Research Letters

View full text Add to dashboard Cite

Climate models show a robust negative feedback in the midlatitudes, coincident with an increase in cloud liquid in the mixed‐phase region of the control climate. This “mixed‐phase feedback” is normally attributed to a feedback caused by a phase change feedback (ice to liquid). Here we use an aquaplanet configuration to investigate this in more detail. We use high‐frequency instantaneous diagnostics and composite them in ascending and descending regimes. We find that a large fraction of the increase in cloud liquid water in the mixed‐phase region does not significantly contribute to the radiative feedback due to a masking effect of the ice cloud above. Using some simple arguments and approximate calculations, we estimate that about one third of the total shortwave negative radiative feedback is driven by a phase change feedback, whereas the rest of the feedback is driven by changes in ice and warm liquid clouds.

show abstract

The Met Office Unified Model Global Atmosphere 7.0/7.1 and JULES Global Land 7.0 configurations

Cited by 424 publications

References 224 publications

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

Improved Aerosol Processes and Effective Radiative Forcing in HadGEM3 and UKESM1

The Met Office Global Coupled Model 3.0 and 3.1 (GC3.0 and GC3.1) Configurations

Cloud Condensate and Radiative Feedbacks at Midlatitudes in an Aquaplanet

Contact Info

Product

Resources

About