• Recommended Use
  • The World Climate Research Programme (WCRP) Coordinated Regional Climate Downscaling Experiment (CORDEX) dataset for South Asia region is provided to assist the science community in conducting studies of climate change impacts at regional scales, and to enhance public understanding of possible future climate patterns at the spatial scale of homogenous regions. This dataset is intended for use in scientific research only, and use of this dataset for other purposes, such as commercial applications, and engineering or design studies is not recommended without consultation with a qualified expert. User feedback to improve and validate the dataset for modeling usage is appreciated.
  • Email comments to sanjay@tropmet.res.in, cccroutreach@tropmet.res.in
  • Dataset and Methods
  • The WCRP CORDEX foster international partnership in order to produce an ensemble of high-resolution past and future climate projections at regional scale. This CORDEX dataset is comprised of downscaled climate scenarios for the South Asia region that are derived from the Atmosphere-Ocean coupled General Circulation Model (AOGCM) runs conducted under the Coupled Model Intercomparison Project Phase 5 (CMIP5) [Taylor et al. 2012] and using three of the four greenhouse gas emissions scenarios known as Representative Concentration Pathways (RCPs) [Meinshausen et al. 2011]. The CMIP5 AOGCM runs were developed in support of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). The coarser spatial resolution ranging from 1.0° to 3.8°, and systematic error (called bias) of these AOGCMs limits the examination of possible impacts of climate change and adaptation strategies on a smaller scale. The CORDEX South Asia dataset includes dynamically downscaled projections from the 10 models and scenarios for which daily scenarios were produced and distributed under CMIP5. The purpose of these datasets is to provide a set of high resolution (50 km) regional climate change projections that can be used to evaluate climate change impacts on processes that are sensitive to finer-scale climate gradients and the effects of local topography on climate conditions.

    The dynamical downscaling method using high resolution limited area regional climate models (RCMs) utilizes the outputs provided by AOGCMs as lateral boundary condition to provide physically consistent spatiotemporal variations of climatic parameters at spatial scales much smaller than the AOGCMs’ grid. The RCMs by resolving the topographical details, coastlines, and land-surface heterogeneities allow the reproduction of small-scale processes and information that are most useful for impact assessment and in decision making for adaptation (Flato et al. 2013). An initial assessment of the ability of the CORDEX RCMs to simulate the general characteristics of the Indian climate indicated that the geographical distribution of surface air temperature and seasonal precipitation in the present climate for land areas in South Asia is strongly affected by the choice of the RCM and boundary conditions (i.e. driving AOGCMs), and the downscaled seasonal averages are not always improved (Sanjay et al. 2017).
  • File Format and Data Access
  • The CORDEX Archive Design document (Cordex Archive Specifications) specifies technical aspects of CORDEX archive file and data formats, as well as archive content. The data is published on the Earth System Grid Federation (ESGF) data nodes by the contributing CORDEX modeling centers after checking for their compliance with the specifications outlined in the archive design document using the tools available for automated quality assurance. The ESGF maintains a global system of federated data centers that allow access to the largest archive of climate data world-wide. Data files comply with the NetCDF format, version 4 compressed with zlib deflation, using the NetCDF 4 classic data model. The CF convention 1.4 is followed.

    CCCR-IITM is the nodal agency for coordinating the CORDEX modeling activity in South Asia (https://www.wcrp-climate.org/wcrp-regional-activities/ra-asia). The CCCR-IITM and several international partner institutions have contributed towards generation and evaluation of regional climate simulations for CORDEX South Asia. Table 1 lists the details of the 17 CORDEX South Asia RCM outputs available on ESGF. This dataset includes the ensemble of high resolution (50 km) downscaled projections of regional climate and monsoon over South Asia until 2100 generated by CCCR-IITM using the RegCM4 RCM developed and maintained by ICTP (Giorgi et al. 2012). The CORDEX South Asia output from this IITM-RegCM4 RCM are archived and published on the CCCR-IITM ESGF data node (http://cccr.tropmet.res.in/home/esgf_node.jsp) for dissemination to users. The list of CORDEX South Asia (domain WAS-44, WAS-44i) multi-model output variables available for download from ESGF and the details for data access are provided on the webpage: (http://cccr.tropmet.res.in/home/esgf_data.jsp)

    Additionally, the raw CORDEX South Asia RCM outputs shared by the modeling partners, which do not strictly conform to the CORDEX archive design specifications, are archived and published on the CCCR-IITM climate data portal designed to facilitate the dissemination of climate information using a publicly accessible FTP and web-based interface (http://cccr.tropmet.res.in/home/old_portals.jsp). Table 2 lists the details of the RCM outputs available on this CORDEX South Asia regional data bank. The details of the few selected CORDEX South Asia multi-model output variables available for download are provided on the webpage: (http://cccr.tropmet.res.in/home/ftp_data.jsp)
  • Acknowledgment
  • For publications that use the CORDEX South Asia model outputs, an appropriate credit as mentioned in the (Cordex Terms of Use), must be given to the data providers by an acknowledgement similar to the following: “The World Climate Research Programme's Working Group on Regional Climate, and the Working Group on Coupled Modelling, former coordinating body of CORDEX and responsible panel for CMIP5 are gratefully acknowledged. The climate modeling groups (listed in Table 1 and Table 2) are sincerely thanked for producing and making available their model output. The authors thank the Earth System Grid Federation (ESGF) infrastructure and the Climate Data Portal hosted at the Centre for Climate Change Research (CCCR), Indian Institute of Tropical Meteorology (IITM) for providing CORDEX South Asia data.”
  • References:
  • Dobler, A., and B. Ahrens (2008)
    Precipitation by a regional climate model and bias correction in Europe and South Asia, Meteorol. Z., 17, 499–509.
  • Flato, G., J. and Coauthors, 2013: Evaluation of Climate Models. In: Climate Change 2013:
    The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  • Giorgi, F. and Coauthors (2012)
    RegCM4: model description and preliminary tests over multiple CORDEX domains. Clim Res 52:7–29.
  • McGregor, J. L., and M. R. Dix (2001)
    The CSIRO Conformal-Cubic Atmospheric GCM. IUTAM Symposium on Advances in Mathematical Modelling of Atmosphere and Ocean Dynamics, P. F. Hodnett, Ed., Kluwer: Dordrecht, 197–202.
  • Meinshausen M., S.J. Smith, K. Calvin, J.S. Daniel, M.L.T. Kainuma, and et al., 2011:
    The RCP greenhouse gas concentrations and their extensions from 1765 to 2300. Climatic Change, 109, 213-241.
  • Sabin, T. P. and Coauthors (2013)
    High resolution simulation of the South Asian monsoon using a variable resolution global climate model. Clim Dyn 41:173–194. DOI 10.1007/s00382-012-1658-8.
  • Samuelsson, P. and Coauthors (2011)
    The Rossby Centre regional climate model RCA3: Model description and performance. Tellus, 63A, 4–23.
  • Sanjay J., M.V.S. Ramarao, M. Mujumdar and R. Krishnan, 2017:
    Regional climate change scenarios. Chapter of book: Observed Climate Variability and Change over the Indian Region. Editors: M. N. Rajeevan and Shailesh Nayak, Springer Geology, pp. 285-304, doi: 10.1007/978-981-10-2531-0.
  • Taylor K. E., R. J. Stouffer, G. A. Meehl, 2012:
    An Overview of CMIP5 and the Experiment Design. Bull. Amer. Meteor. Soc., 93, 485–498.
  • Teichmann C, Eggert B, Elizalde A, Haensler A, Jacob D, Kumar P, Moseley C, Pfeifer S, Rechid D, Remedio A, Ries H, Petersen J, Preuschmann S, Raub T, Saeed F, Sieck K, Weber T (2013)
    How does a regional climate model modify the projected climate change signal of the driving GCM: A study over different CORDEX regions using REMO, Atmosphere, 4(2), 214-236.