Parametrization of area cloud fraction

Boutle, Ian; Morcrette, C. J.

doi:10.1002/asl.293

Cited by 27 publications

(21 citation statements)

References 18 publications

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“…Finally, the methodology will be used to target and test model developments which are expected to strongly impact cloud predictions such as changes to the cloud, microphysics, convection and boundary-layer parametrization schemes. These will include a parametrization designed to improve the forecasts of cloud cover below capping inversions (Boutle and Morcrette, 2010) and changes to the convection scheme aimed at improving the diurnal cycle of convection (Stratton and Stirling, 2011, pers. comm.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of two cloud parametrization schemes using ARM and Cloud‐Net observations

Morcrette

O’Connor

Petch

2011

Quart J Royal Meteoro Soc

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† The contribution of these authors was written in the course of their employment at the Met Office, UK, and is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.Ground-based remote-sensing observations from Atmospheric Radiation Measurement (ARM) and Cloud-Net sites are used to evaluate the clouds predicted by a weather forecasting and climate model. By evaluating the cloud predictions using separate measures for the errors in frequency of occurrence, amount when present, and timing, we provide a detailed assessment of the model performance, which is relevant to weather and climate time-scales. Importantly, this methodology will be of great use when attempting to develop a cloud parametrization scheme, as it provides a clearer picture of the current deficiencies in the predicted clouds.Using the Met Office Unified Model, it is shown that when cloud fractions produced by a diagnostic and a prognostic cloud scheme are compared, the prognostic cloud scheme shows improvements to the biases in frequency of occurrence of low, medium and high cloud and to the frequency distributions of cloud amount when cloud is present. The mean cloud profiles are generally improved, although it is shown that in some cases the diagnostic scheme produced misleadingly good mean profiles as a result of compensating errors in frequency of occurrence and amount when present. Some biases remain when using the prognostic scheme, notably the underprediction of mean ice cloud fraction due to the amount when present being too low, and the overprediction of mean liquid cloud fraction due to the frequency of occurrence being too high.

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Section: Discussionmentioning

confidence: 99%

Evaluation of two cloud parametrization schemes using ARM and Cloud‐Net observations

Morcrette

O’Connor

Petch

2011

Quart J Royal Meteoro Soc

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“…Each process in the model acts as a source/sink of these prognostic variables, including the convection scheme, so that PC2 represents both convective and large-scale cloud in the model. The GA1.0 implementation of the PC2 scheme is modified through use of the parameterisation of Franklin et al (2012) to modify the PC2 ice cloud fraction and the cloud area scheme of Boutle and Morcrette (2010) to account for the effects of coarse vertical resolution on low-level cloud cover.…”

Section: Access13mentioning

confidence: 99%

The ACCESS coupled model: description, control climate and evaluation

Bi¹,

Dix²,

Marsland³

et al. 2013

440

273

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The Australian Community Climate and Earth System Simulator coupled model (ACCESS-CM) has been developed at the Centre for Australian Weather and Climate Research (CAWCR), a partnership between CSIRO 1 and the Bureau of Meteorology. It is built by coupling the UK Met Office atmospheric unified model (UM), and other sub-models as required, to the ACCESS ocean model, which consists of the NOAA/GFDL 2 ocean model MOM4p1 and the LANL 3 sea-ice model CICE4.1, under the CERFACS 4 OASIS3.2-5 coupling framework. The primary goal of the ACCESS-CM development is to provide the Australian climate community with a new generation fully coupled climate model for climate research, and to participate in phase five of the Coupled Model Inter-comparison Project (CMIP5). This paper describes the ACCESS-CM framework and components, and presents the control climates from two versions of the ACCESS-CM, ACCESS1.0 and AC-CESS1.3, together with some fields from the 20 th century historical experiments, as part of model evaluation. While sharing the same ocean sea-ice model (except different setups for a few parameters), ACCESS1.0 and ACCESS1.3 differ from each other in their atmospheric and land surface components: the former is configured with the UK Met Office HadGEM2 (r1.1) atmospheric physics and the Met Office Surface Exchange Scheme land surface model version 2, and the latter with atmospheric physics similar to the UK Met Office Global Atmosphere 1.0 including modifications performed at CAWCR and the CSIRO Community Atmosphere Biosphere Land Exchange land surface model version 1.8. The global average annual mean surface air temperature across the 500-year preindustrial control integrations show a warming drift of 0.35 °C in ACCESS1.0 and 0.04 °C in AC-CESS1.3. The overall skills of ACCESS-CM in simulating a set of key climatic fields both globally and over Australia significantly surpass those from the preceding CSIRO Mk3.5 model delivered to the previous coupled model inter-comparison. However, ACCESS-CM, like other CMIP5 models, has deficiencies in various aspects, and these are also discussed.

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“…The methods used to conduct these modifications have been described in the relevant papers (Shonk et al 2010, Franklin et al 2012, Ma et al 2012, Boutle and Morcrette 2010. Only brief summaries are given in the next section.…”

Section: Modifications To Um Atmospheric Physicsmentioning

confidence: 99%

“…The area cloud fraction for the cloud layer is assigned as the maximum value of the volume cloud fraction from the three sublevels and this is used within the radiation scheme. Boutle and Morcrette (2010) extended this method to work with the PC2 to improve the representation of liquid water cloud forming near capping inversions, which were poorly represented due to the coarse vertical resolution. This scheme was implemented in UM7.3 for ACCESS Modifications to the air-sea flux scheme Air-sea exchanges in a coupled ocean-atmosphere model are important to the accurate simulation of SST because the atmospheric surface stress exerted on the ocean surface is largely responsible for the distribution of the ocean surface current and subsequently the distribution of SST.…”

Section: Evaluation Of Physical Modifications In Accessmentioning

confidence: 99%

Modifications to atmospheric physical parameterisations aimed at improving SST simulations in the ACCESS coupled model

Sun¹,

Franklin²,

Zhou³

et al. 2013

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The Australian Community Climate and Earth System Simulator (ACCESS) has been developed at the Centre for Australian Weather and Climate Research. It is a coupled modeling system consisting of ocean, atmosphere and land surface. The ACCESS atmospheric component is the UK Met Office Unified Model (UM). The initial results from the ACCESS coupled model had significant errors in the sea surface temperature (SST). It has been identified that the SST bias is largely due to errors in the representation of clouds. We have found that the use of the homogenous cloud distribution within model grid-boxes produced an underestimation of solar radiation reaching the surface, causing a cooling effect. The model cloud scheme PC2 does not produce enough high cloud cover, which also led to a cooling effect. These two deficiencies have been largely remedied by the implementation of the triple-cloud scheme and a modification to the ice cloud fraction parameterisation in the PC2 cloud scheme. We have also modified the air-sea flux exchange scheme to improve the simulation of ocean currents. These modifications have led to significant improvements in the simulation of SST in ACCESS.

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Parametrization of area cloud fraction

Cited by 27 publications

References 18 publications

Evaluation of two cloud parametrization schemes using ARM and Cloud‐Net observations

Evaluation of two cloud parametrization schemes using ARM and Cloud‐Net observations

The ACCESS coupled model: description, control climate and evaluation

Modifications to atmospheric physical parameterisations aimed at improving SST simulations in the ACCESS coupled model

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