Email from Mich to TIRA
Dear Masa,
Yes, the S-RIP and ORA-IP efforts presented during the TIRA conf calls and related discussions suggest there are opportunities to better coordinate our efforts which may ultimately also result in more integrated reanalysis science products and subsequent exploitation by the user community.
I think it was Mike who actually offered to initiate the discussion, but here are some suggested bullet points from my perspective that we could address during our next conf call:
- common infrastructure, protocols, standards: CMIP's success to a large extent results from the community agreeing on a set of basic principles around those, which is now expanding into obs4MIPs (https://www.earthsystemcog.org/projects/obs4mips/) and ana4MIPs (https://esgf.nccs.nasa.gov/projects/ana4mips/). To what extent can TIRA push in this direction and build on ESGF (https://esgf.llnl.gov/)? I suspect this is almost a prerequisite.
- intercomparison efforts: we have already a guiding document regarding best practices for data set assessments (https://www.wcrp-climate.org/WDAC/document/WDAC_Report_DataSetQualityAssessments.pdf) but we now need to think this through as you Masa pointed out in terms of diagnostics and metrics, and maybe also uncertainties, on the basis of what reference observations, etc
- synthesis products/climate indicators down the line: how can we potentially leverage the above to serve a broad range of purposes (assessment reports, end-users, etc). There are lots of discussions these days on this, in particular within GCOS, in the context of the UNFCCC Global Stocktake. I expect reanalyses to play their role in this. The EU Copernicus Climate Change Service (adding Jean-Noel in CC) for example is embarking on this too.
Email Reply from Masatomo to TIRA 6 APR 2017
It might be good for us TIRA to do a small, pilot
project, e.g., writing a paper on ... comparison of some key diagnostics from all available
reanalyses, which is e.g. useful for forthcoming IPCC AR6 report.
(The key diagnostics may include: global surface temperature, sea ice extent, area of land covered by snow and Ice, heat waves, as in the GCOS document attached in the previous Mich's email. And, I think that we may not need to worry too much about reference observations for these - showing the reanalysis intercomparison would be still very useful.)
(... and here, I need to point out that we should think about covering all types of reanalyses, not only global atmospheric reanalyses and ocean reanalyses but ...)
(and of course, we will use Jerry's and Gil's tools)
Doing such a small project within us TIRA (perhaps plus some more researchers) would be good for us to further think about Mich's other points, such as "common infrastructure, protocols, standards" and "synthesis products/climate indicators down the line"
- we will also know key persons and key documents relevant to these.
With my best wishes,
Masatomo
Potential Metrics
I think a good set of metrics might be related to the definition of storm track, as in monthly mean v prime square, or kinetic energy. Mid latitude obs are reliably assimilated and dynamics are handled well, but the reproduction of these in global models would need validated.
Also a point of discussion at Obs4MIPS
The Obs4MIPS group had a discussion about what variables they wanted for IPCC present day validation, from reanalyses. Surface air temperature doesn't add too much, since there are pure obs data sets (e.g. CRU). I stressed care with atmospheric water vapor profiles, as the differences among reanalysis gets large in the tropics. Heights, temperature and generally winds are generally comparable among reanalysis. Variables too closely related to clouds likely have too much uncertainty. However, global observations of surface downward longwave radiation are lacking and this is a key component of the energy balance.