A Mass Flux Convection Scheme with Representation of Cloud Ensemble Characteristics and Stability-Dependent Closure

Gregory, D.; Rowntree, P. R.

doi:10.1175/1520-0493(1990)118<1483:amfcsw>2.0.co;2

Cited by 862 publications

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“…Convection is parameterized by a penetrative mass flux scheme (Gregory and Rowntree, 1990) in which buoyant parcels are modified by entrainment and detrainment to represent an ensemble of convective clouds. The convection scheme has been tested using 222 Rn experiments; the agreement with observations is reasonable (Stevenson et al, 1998b).…”

Section: Climate Modelmentioning

confidence: 99%

Impact of climate change on tropospheric ozone and its global budgets

2008

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Abstract.We present the chemistry-climate model UM CAM in which a relatively detailed tropospheric chemical module has been incorporated into the UK Met Office's Unified Model version 4.5. We obtain good agreements between the modelled ozone/nitrogen species and a range of observations including surface ozone measurements, ozone sonde data, and some aircraft campaigns.Four 2100 calculations assess model responses to projected changes of anthropogenic emissions (SRES A2), climate change (due to doubling CO 2 ), and idealised climate change-associated changes in biogenic emissions (i.e. 50% increase of isoprene emission and doubling emissions of soil-NO x ). The global tropospheric ozone burden increases significantly for all the 2100 A2 simulations, with the largest response caused by the increase of anthropogenic emissions. Climate change has diverse impacts on O 3 and its budgets through changes in circulation and meteorological variables. Increased water vapour causes a substantial ozone reduction especially in the tropical lower troposphere (>10 ppbv reduction over the tropical ocean). On the other hand, an enhanced stratosphere-troposphere exchange of ozone, which increases by 80% due to doubling CO 2 , contributes to ozone increases in the extratropical free troposphere which subsequently propagate to the surface. Projected higher temperatures favour ozone chemical production and PAN decomposition which lead to high surface ozone levels in certain regions. Enhanced convection transports ozone precursors more rapidly out of the boundary layer resulting in an increase of ozone production in the free troposphere. Lightning-produced NO x increases by about 22% in the doubled CO 2 climate and contributes to ozone production.The response to the increase of isoprene emissions shows that the change of ozone is largely determined by background NO x levels: high NO x environment increases ozone producCorrespondence to: G. Zeng (guang.zeng@atm.ch.cam.ac.uk) tion; isoprene emitting regions with low NO x levels see local ozone decreases, and increase of ozone levels in the remote region due to the influence of PAN chemistry. The calculated ozone changes in response to a 50% increase of isoprene emissions are in the range of between −8 ppbv to 6 ppbv. Doubling soil-NO x emissions will increase tropospheric ozone considerably, with up to 5 ppbv in source regions.

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Section: Climate Modelmentioning

confidence: 99%

Impact of climate change on tropospheric ozone and its global budgets

2008

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“…Therefore, the mechanism responsible for decadal varying forecast quality of the ISMR also deserves further exploration on the basis of the interaction between the monsoon Hadley and Walker circulations and slowly varying external forcings, particularly from tropical Indian Ocean and Pacific. 19601965197019751980198519901995 Based on the analysis in Section 4.1, one wonders why the MME shows better quality in predicting AIR interannual variability than each single-model ensemble. Does it relate mainly to increased ensemble size in the MME?…”

Section: The Forecast Quality Of Air Interannual Variabilitymentioning

confidence: 99%

Evaluation of the DEMETER performance for seasonal hindcasts of the Indian summer monsoon rainfall

Rodó

Doblas‐Reyes

2011

Intl Journal of Climatology

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On the basis of the observed all-India rainfall (AIR), Climate Prediction Center (CPC) merged analysis of precipitation (CMAP), and the multimodel rainfall simulated in the Development of a European multimodel ensemble system for seasonal to interannual prediction (DEMETER) project, the model performance in terms of forecast quality of the seasonal mean Indian summer monsoon rainfall (ISMR) was evaluated. The approach used included the individual model (single-model ensemble) comparison as well as its comparison with the multimodel ensemble (MME). The results obtained reveal that systematic biases are the main source of the low skill in predicting the ISMR, while improved reproduction of interannual variability may increase the overall forecast quality for the ISMR. The MME shows superior performance in reproducing AIR features than the single-model ensembles. This improved forecast quality achieved by the MME with respect to the ISMR variations primarily depends on model performance and secondly on ensemble size. The MME has improved capability of simulating the ISMR variations during 1972-1990 decades, whereas it exhibits a lower performance in the 1990s. The reason of this decadal varying forecast quality clearly deserves more investigation. In summary, these results suggest that the MME's increase in skill absolutely depends on enhancing the individual model quality.

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“…The model shares its dynamics and physics with the atmospheric component of the Hadley Centre Global Environment Model (HadGEM1; Martin et al, 2006). Its convection scheme is based on the mass-flux scheme of Gregory and Rowntree (1990) but with significant modifications (see Martin et al, 2006, and references therein for details). The cloud scheme is based on Smith (1990) and it has the first-order turbulence closure boundary-layer scheme of Lock et al (2000).…”

Section: Single-column Models (Scms)mentioning

confidence: 99%

Modelling convective processes during the suppressed phase of a Madden–Julian oscillation: Comparing single‐column models with cloud‐resolving models

Woolnough

Blossey

et al. 2010

Quart J Royal Meteoro Soc

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The role of convective processes in moistening the atmosphere during suppressed periods of the suppressed phase of a Madden-Julian oscillation is investigated in cloud-resolving model (CRM) simulations, and the impact of moistening on the subsequent evolution of convection is assessed as part of a Global Energy and Water Cycle Experiment Cloud System Study (GCSS) intercomparison project. The ability of single-column model (SCM) versions of a number of state-of-the-art climate and numerical weather prediction models to capture these convective processes is also evaluated. During the suppressed periods, the CRMs are found to simulate a maximum moistening around 3 km, which is associated with a predominance of shallow convection. All SCMs produce adequate amounts of shallow convection during the suppressed periods, comparable to that seen in CRMs, but the relatively drier SCMs have higher precipitation rates than the relatively wetter SCMs and CRMs. The relatively drier SCMs dry, rather than moisten, the lower troposphere below the melting level. During the transition periods, convective processes act to moisten the atmosphere above the level at which mean advection changes from moistening to drying, despite an overall drying effect for the column. The SCMs capture some essence of this moistening at upper levels. A gradual transition from shallow to deep convection is simulated by the CRMs and the wetter SCMs during the transition periods, but the onset of deep convection is delayed in the drier SCMs. This results in lower precipitation rates for these SCMs during the active periods, although much better agreement exists between the models at this time.

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A Mass Flux Convection Scheme with Representation of Cloud Ensemble Characteristics and Stability-Dependent Closure

Cited by 862 publications

References 0 publications

Impact of climate change on tropospheric ozone and its global budgets

Impact of climate change on tropospheric ozone and its global budgets

Evaluation of the DEMETER performance for seasonal hindcasts of the Indian summer monsoon rainfall

Modelling convective processes during the suppressed phase of a Madden–Julian oscillation: Comparing single‐column models with cloud‐resolving models

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