RegCM4: Model description and preliminary tests over multiple CORDEX domains

Climate Research (Impact Factor: 2.5). 01/2011; 936:577X. DOI: 10.3354/cr01018

ABSTRACT A new version of the RegCM regional climate modeling system, RegCM4, has been recently developed and made available for public use. Compared to previous versions, RegCM4 includes new land surface, planetary boundary layer, and air-sea flux schemes, a mixed convection and tropical band configuration, modifications to the pre-existing radiative transfer and boundary layer schemes, and a full upgrade of the model code towards improved flexibility, portability, and user friendliness. The model can be interactively coupled to a 1D lake model, a simplified aerosol scheme (including organic carbon, black carbon, SO4, dust, and sea spray), and a gas phase chemistry module (CBM-Z). After a general description of the model, a series of test experiments are presented over 4 domains prescribed under the CORDEX framework (Africa, South America, East Asia, and Europe) to provide illustrative examples of the model behavior and sensitivities under different climatic regimes. These experiments indicate that, overall, RegCM4 shows an improved performance in several respects compared to previous versions, although further testing by the user community is needed to fully explore its sensitivities and range of applications.

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    • "Nevertheless, after all such advancements the simulation models need a long way to go to simulate regional precipitation and cloud and aerosol interactions properly. As far as the involvement of these climate models to carry out the hydrological studies is related both the Regional Climate Models (RCMs) as was studied by Wang et al. (2004) and Block (2009), Haddeland et al. (2011), Ghosh and Katkar (2012), Giorgi and Coppola (2012)and Hagemann et al. (2013) reported that the GCMs are generally taken resort to. These climate models are coupled with the Hydrological Models and help simulating input of the regional weather parameters being translated into the changes in the hydrological processes. "
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    ABSTRACT: In the wake of changing climate the present water crisis seems to tighten its hold on the Mankind hence water resources estimation is integral part of planning, development and management of water resources of the country and the estimation of water resource is based on several hydrological and meteorological parameters. Rainfall is the main source of the ground and surface water resources. Recently due to anticipated climate change it is projected that spatial and temporal pattern of rainfall in different part of the country will be change and there will be increase in intensity of rainfall greater monsoon variability. This unprecedented change is expected to have severe impact on the on the water resource and finally on water resource estimation for future planning and management. Apart from climate change, both the ever increasing population and the rapidly changing land use patterns have left the major river basins of the India in a bleak uncertainty to keep up the required runoff. For planning and management, the climate and the hydrological modellers have begun working out runoff projections. During recent years, the Global Climate Models (GCMs) and Regional Climate Models (RCMs) driven hydrological models are in frequent use to draw such projections. But the projections have been often found to lack of reliability. Very recently, there is another emerging field of multi-model ensembles that has added feather to cap of the climate modeling community but this field is yet to be tried in many of the basin runoff-studies especially in the Indian perspective. There is a dire need for more research input assessing the future runoff as far as the Indian River basins are concerned. The climate models are being improved day by day so are the hydrological models. The multi-model ensembles are expected to bring out more reliability in the model outputs regarding the future runoff regimes of the basins than that could be brought about using individual models. The present study is a brief reviewof the model-based projections made for the some of the major river basins of the world. This attempt also seeks to bring forth the basin wise state-of-the-art research activities of such a kind so that the unexplored horizons of model based hydrological research could be taken up as newer research challenges like eg. in India there hasn’t yet been much basin scale studies conducted using multi-model ensembles. Therefore it is suggested that detailed studies to be taken up to assess the impact of climate change on the various parameters involved in estimation of water resources and asses water resource keeping in view the climate change for more realistic future planning and integrated water resource management.
    12/2015; 4:730-738. DOI:10.1016/j.aqpro.2015.02.094
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    • "Previous studies also found that the Emanuel scheme tends to produce excessive rainfall over land while the Grell scheme cannot capture major events over ocean (Gianotti et al. 2012; Adeniyi 2014). Giorgi et al. (2012) suggests that Grell scheme can be used over land with Emanuel scheme over ocean to overcome these weaknesses. Here, it is further noticed from Table 2 that among the results of E-C-Z2, GAS-C-Z2 and GFC-C-Z2, GFC produces the smallest MAB and largest COR over land area, while the results from GAS have the largest MAB and smallest COR over land area. "
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    ABSTRACT: This study evaluates the sensitivity of summertime rainfall simulations over East-to-southeast Asia and the western north Pacific in the regional climate model version 4 (RegCM4) to cumulus (including Grell with Arakawa–Schubert type closure, Grell with Fritsch–Chappell type closure, and Emanuel), land surface (Biosphere–atmosphere transfer scheme or BATS, and the community land model or CLM) and ocean surface (referred to as Zeng1, Zeng2 and BATS1e in the model) schemes by running the model with different combinations of these parameterization packages. For each of these experiments, ensemble integration of the model was carried out in the extended boreal summer of May–October from 1998 to 2007. The simulated spatial distribution, intensity and inter-annual variation of the precipitation, latent heat flux, position of the subtropical high and tropical cyclone genesis patterns from these numerical experiments were analyzed. Examinations show that the combination of Emanuel, CLM and Zeng2 (E-C-Z2) yields the best overall results, consistent with the fact that physical mechanisms considered in E-C-Z2 tend to be more comprehensive in comparison with the others. Additionally, the rainfall quantity is found very sensitive to sea surface roughness length, and the reduction of the roughness length constant (from 2 × 10−4 to 5 × 10−5 m) in our modified BATS1e mitigates the drastic overestimation of latent heat flux and rainfall, and is therefore preferable to the default value for simulations in the western north Pacific region in RegCM4.
    Climate Dynamics 07/2015; DOI:10.1007/s00382-015-2714-y · 4.67 Impact Factor
    • "From the four options to represent subgrid-scale convection, a mixed convection configuration is chosen, whereby the Grell (Grell, 1993) with the Fritsch and Chappell (1980) closure assumption and the MIT Emanuel (Emanuel, 1991) schemes are used over land and ocean grid points respectively. This combined scheme was demonstrated to perform better in most Coordinated Regional Downscaling Experiment (CORDEX) domains (Giorgi et al., 2012) and also in the preliminary test runs over the South African domain (not shown). The biosphere atmosphere transfer scheme (BATS, Dickinson et al., 1993) is chosen to represent land surface processes. "
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    ABSTRACT: This study presents an assessment of the skill and economic benefits of a seasonal forecast carried out by nine-member ensembles of regional and global models over southern Africa for the period of 1991–2002. The regional ensemble seasonal hindcasts were conducted at a resolution of 25 km by driving RegCM4 with the corresponding ensembles of the European Centre for Medium-Range Weather Forecasts (ECMWF) seasonal hindcasts. Skill and cost/loss ratio analysis were carried out on the probabilistic hindcasts to assess how much added value a regional model would bring over the driving ECMWF forecasts. RegCM4 shows an added value over most areas of southeastern Africa where the skill of the global circulation model (GCM) is already positive. In terms of economic benefits, RegCM4 brings additional benefits for southeastern Africa either by benefiting more users with interest in larger cost/loss ratio or by providing a higher economic value for users with small cost/loss ratio. Additional RegCM4 simulations with the same resolution were performed using a near ‘perfect’ boundary conditions with ‘continuous (climate)’ and ‘reinitialized’ modes to test the impact of land surface initialization/ spin up time on the seasonal mean precipitation simulation. Evaluation of the ‘perfect’ boundary forced simulations reveals that the regional model not only generates finer spatial-scale features that are missing in the ECMWF GCM, in terms of the December to April (DJFMA) climatology, but also reduced the wet bias of the driving GCM. Land surface initialization is found to have less impact on the DJFMA seasonal mean rainfall for forecasts initialized on 1 November, suggesting that 1 month is enough to recover from the shock of poor soil moisture initialization.
    International Journal of Climatology 06/2015; DOI:10.1002/joc.4375 · 3.16 Impact Factor
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