1. Coordinated Regional Downscaling Experiment:
CMIP6 & Regional Information for IPCC
CORDEX Scientific Vision:
To advance and coordinate the science and application of regional climate downscaling through global partnerships
Goals:
To better understand relevant regional/local climate phenomena, their variability and changes, through downscaling.
To evaluate and improve regional climate downscaling models and techniques
To produce coordinated sets of regional downscaled projections worldwide
To foster communication and knowledge exchange with users of regional climate information

2. CORDEX: A CMIP6 Diagnostic MIP
Primary CMIP6 Question Addressed: How can we assess future climate changes given climate variability, predictability and uncertainties in scenarios?
Primary WCRP Grand Challenges Addressed:
Regional climate information (though this GC is evolving)
Weather and climate extremes
Potential Coordination: HighResMIP
all three of the key questions for CMIP6 through regional simulations with different climate forcings (CMIP Key Question 1), evaluation of physical processes affecting added value and biases in the downscaled results (CMIP Key Question 2) and characterization of the impact of unforced variability, both internally generated and via ensemble boundary conditions, on the ratio of regional climate change signals versus the noise of unforced variability (CMIP Key Question 3).

3. CORDEX: A CMIP6 Diagnostic MIP
The GCMs are consistent with the observed large-scale climate statistics, while the RCM simulations produce greater consistency with the fine scale statistics.
Empirical Probability Density Function (PDF, i.e. frequency vs. intensity) of daily precipitation events over a West Africa region [73] in: simulations with the regional climate model RegCM4 (50 km grid spacing) driven by the global models MPI and HadGCM (see [73] for details on the models), coarse scale (GPCP, 1.0° [74]) and fine scale (TRMM, 0.25° [75]) observations. Data are for the historical period in the models, for GPCP and for TRMM. The figure is adapted from [73].

4. CORDEX: A CMIP6 Diagnostic MIP
Connectivity to DECK:
Analysis of downscaled CMIP DECK simulations (30 years) for the pre-industrial control compared to the transient forcing cases (e.g., CMIP6 Historical) will determine potential regional climate-change detection.
Connectivity to CMIP6 Historical and Scenario Simulations: 
1. Analysis during the historical period ( ) will indicate where and when the downscaling provides regional detail of physical behavior that agrees better with observations than the driving GCM output and provides robust additional fine scale climate information.
2. Analysis during the historical period ( , though ideally, ) from downscaling of multiple realizations by the same GCM will indicate the magnitude of regional unforced variability. When coupled with analysis of downscaled projections ( ), results will assess where and when the downscaling provides regional detail of physical behavior that exceeds noise levels of unforced internal variability.

5. CORDEX: A CMIP6 Diagnostic MIP
Targeted GCM simulations should:
cover as well as possible the range of GCM climate model sensitivity;
provide acceptable quality of historical climate simulations in the regions where they supply boundary conditions;
provide acceptable quality of historical climate simulations for important large-scale features affecting regional climates, such as ENSO, NAO, etc.;
have a distinctive model development history.
Ideal GCM output for downscaling: 
1) Sufficient for dynamical and empirical statistical downscaling (transient climate-change simulation)
2) Multiple realizations of the same GCM for both the pre-industrial and transient climate-change simulations [explore unforced variability]
3) Pre-industrial control runs (CMIP DECK) and runs with changes in only one climate forcing (if part of CMIP6) [explore regional detection and attribution]

6. CMIP6 & CORDEX – Flagship Pilot Studies
First FPS call closed 15 Feb. 2016
8 proposals (under review) from 6 CORDEX regions
Coordinate developments in conv.-permitting climate sim.
Must have
Fine-scale processes important to region’s climate (physical basis)
Observational basis for verification (analysis basis)
User applications (VIA basis)
Potential connection with other WCRP programs, esp. GEWEX
Details:
·         WAS sent by A.P. Dimri on Indian Summer Monsoon. All okey except that the proposed reviewers are both from the same institution in India so maybe a bit biased.
·         EUR sent by Piet Termonia on gathering Belgian regional downscaling expertise. All okey but a bit longer application than expected and perhaps the reviewers should be reconsidered.
·         NAM sent by Andrew Ireson on Cold regions LSS model intercomparison. All okey.
·         EUR+MED sent by Stefan Sobolowski on Convective phenomena. All okey.
·         EUR sent by Diana Rechid on Impact of land use changes on climate. All okey.
·         SAM sent by Maria Bettolli on Extreme precipitation events. All okey.
·         AFR sent by Chris Lennard on Assessing impact of global warming targets. All okey.
·         MED sent by Solomon Fabien on the Role of the natural an anthropogenic aerosols. All okey

7. CMIP6 & CORDEX – CORE Simulations
CORDEX Coordinated Output for Regional Evaluations (CORE)
In development
Motivated by IPCC Workshop on Reg. Climate (Sept. 2015)
Elements
Succinct set of downscalings for each region
Provide a core foundation for additional work by others
Span plausible range of climate change => 3 distinct GCMs?
CMIP5? Historical + RCP8.5?
3-4 RCMs?
ESD methods?
Resolution?

8. CORDEX: A CMIP6 Diagnostic MIP
Beyond the details, many broad questions to address: 
What are realistic expectations for input to the AR6?
Are contributions possible to IPCC special reports?
What timeline(s) are needed?
. . .

9. CORDEX in CMIP6: Details
Preferred output period: for transient climate change (RCP8.5, RCP4.5 and RCP2.6 for ); 30 years of pre-industrial control.
- For dynamical downscaling:
6-hourly instantaneous surface pressure
6-hourly instantaneous three-dimensional fields of temperature, atmospheric specific humidity, zonal wind and meridional wind
- For statistical downscaling, also:
maximum daily surface (2m) temperature
minimum daily surface (2m) temperature
daily surface temperature (2m)
daily surface dewpoint temperature (2m)
daily zonal wind (10m)
daily meridional wind (10m)
daily precipitation
daily precipitable water
monthly sea surface temperature

10. CORDEX in CMIP6: Details
- Supplementary variables that are desirable:
daily soil moisture (vertically integrated)
daily snow density
daily snow albedo
daily low and medium cloud cover
6-hourly instantaneous geopotential height at 850, 700 and 500 hPa