CRTF Telecon - 12-10-2014

Notes from the Telecon

Gil introduced the speakers and emphasized the theme of user needs and applications.

First, Paul Poli described results from a recent users survey commissioned by CORE-CLIMAX, which is a coordinated climate-studies effort among 9 different EU members. The purpose of the survey is to determine how various reanalysis products are being used, who is using them, and the needs of the users. By way of introduction, Paul mentioned that the ECMWF is now administering 2 of 6 services that are part of the European Earth Observing System, the Atmospheric Monitoring and Climate Change services.

The survey obtained a large number of respondents, and the makeup of the respondent pool was likely heavily weighted towards users of the European Reanalysis. For atmospheric reanalyses, most users make use of 3-4 data sets. For oceanic reanalyses, it was noted that the user community appears much more “fragmented”, with a relatively large number of different reanalysis products available. It’s unclear whether this is a good or bad thing, and may also be dependent on the pool of respondents.

Overall, the need for more training in the use of reanalysis data and documentation of observational inputs were two areas that were identified as needing improvement. It was noted that the issues that users identified as having the highest priority to be fixed were also probably the hardest issues to fix.

During Q&A, one question asked if social scientists could be enlisted to help “drill down” into the data, and perhaps to help formulate future follow-on surveys. It was suggested that outreach to social scientists in order to make them aware of this work would be a good thing. It was noted that sorting the responses based on the background of the users and their location (nationality) could be useful additional information. One of the biggest surprises of the survey was the large number of respondents from the private sector, and it seems the energy industry was heavily represented here. In addition, the extensive user comments (often paragraph length) reflected considerable time and attention to the survey on the part of the respondents. The overwhelming consensus was that these reanalysis data sets are very important to a wide range of users from academia, government, and the private sector.

Next, Erica Dolinar presented results from the UND group, which recently undertook an intercomparison of cloud radiative forcing terms among 5 different reanalyses. These were validated using both satellite-based measurements (e.g., TRMM, MODIS, etc.) and ground-based observations from two ARM sites. Detailed comparisons were made using precipitation rate, top of atmosphere (TOA) cloud radiative forcing (CRF), and dynamical quantities such as vertical velocity. Overall, the reanalysis did a good job representing observed large scale features, but there was a tendency for most reanalyses to systematically overestimate or underestimate these quantities, and these systematic biases depended strongly on whether they occurred in regions of pronounced upwelling or downwelling associated with convective precip. Future work will focus in particular on examining additional quantities (e.g., heating rates) within the convective regions, particularly over oceans.

During the Q&A, it was noted that these types of diagnostics could be valuable for validation or QC as a reanalysis data set is being developed/generated. One question was whether all the models have too strong evaporation. In response, it was stated that the treatment of atmosphere/ocean coupling varies among the different systems, which needs to be considered. The need for additional work to determine whether systematic biases in the radiative terms are due to model dynamics or to the physical parameterizations in the models themselves was cited. A question was raised concerning the disagreement between TRMM and other microwave-based observations of precip rates, and whether the observational uncertainty in some of these quantities can be better quantified. Another question was if diurnal or seasonal cycles in the reanalyses have been examined, and this was identified as a potential area for future study.

Finally, Gil reminded everyone to review the outlines for upcoming conference calls and to volunteer to give a presentation. Rapporteurs are also needed. Gil also mentioned that there is a reanalysis-related special session at the Fall AGU, and he advertised an upcoming recap of the S-RIP meeting.