WCRP GEWEX GMPP GCSS PCS NewsJun08

I would like to begin by thanking everyone who contributed to the PCS breakout sessions - either by giving talks, or through participation in the discussions.

There was a strong drive to work within to GCSS framework to tackle a range of problems relevant for the PCS group. While the next main case study will carry out modelling of TWP-ICE (focusing on microphysical aspects, transport and the impact of convection on the TTL), there was a range of suggestions for other case studies. Where someone is willing to lead a case, and there is consensus that is a relevant problem for the PCS group, I will be happy to have it running as a case alongside any ongoing cases.

The breakout sessions were quite large so if you have any points you were unable to raise, or were not able to make the meeting and have any comments on any PCS issues (such as those discussed here), please do e-mail me them.

Jon Petch

Case 5: Transition of tropical convection

This case has progressed well with a paper describing the case study published ( Petch et al. 2008) and a paper comparing NWP models accepted subject to minor revisons by QJ RmetS. Steve Woolnough who is leading the CRM and SCM comparison is not well and we wish him well. Once he recovers, he will finish off the paper describing the results from the SCMs and CRMs.

TWP-ICE: Convective transport, microphysics and the TTL

Ann Fridlind (CRMs) and Maria Russo (LAMs) presented the design and preliminary results for a TWP-ICE model comparison study. It was also revealed that Laura Davies will work with Christian Jakob on the design of an SCM component of this multi-model comparison. More details will follow on this in the coming month or two. We hope to have preliminary results by the end of November (see future meetings).

An idealised study of the role of convection in the TTL

Wojtek Grabowski presented an idealised case for CRMs, specifically to study the role of convection on the TTL. He will be at the ARM meeting in November so this could be discussed further then with a view to releasing this case towards the end of this year if there is sufficient interest. If you have any suggestions or queries about this case in the mean time please do e-mail Wojtek.

AMMA: convection over tropical land

The were preliminary suggestions for an AMMA based case study which could be carried out in the longer term. Background issues were presented by Catherine Rio and Francoise Guichard but at this stage we do not have a specific case or a case leader. I would welcome suggestions along these lines.

Other suggested studies

Brian Mapes and Steve Sherwood suggested other case studied we could consider. Expect to hear more on these in the coming year if they have the chance to advance these plans.

The suggestion by Brian and Zhiming Kuang would be to carry out experiments where the large scale forcing is able to respond the behaviour of the CRM or SCM itself (Kuang 2008). The likely timescale for this case study to be developed would be around a year from now (depending on ARM funding). This can be discussed further at our next meeting (see below).

Given that the TWP-ICE case study is joint with ARM, we agreed that the PCS WG will get together at the ARM joint Cloud Modelling/ Radiative Processes Working Group Meeting this fall. The meeting will be held at the Nassau Inn in Princeton, NJ from Nov 17-21, 2008. You can register online at https://secure2.pnl.gov/rpwg/rpwg.nsf/registration?OpenForm. Many thanks to ARM for allowing us to meet jointly with them.

No further plans to meet were agreed and I would welcome suggestions for this. I am sure the TWP-ICE case will be discussed at the spring ARM meeting. It may make sense to get back together jointly with SPARC at some point to discuss progress on TTL issues and/or if an AMMA case is designed then some joint meeting with others in GEWEX may be appropriate.

Finally I note that on 24-28 Aug 2009 there will be the 6th International Scientific Conference on the Global Energy and Water Cycle and 2nd iLEAPS Science Conference. This will be held in Melbourne and may well be a good place to have a PCS session depending on who can attend this meeting.

Ann Fridlind kindly attended the SSG meeting on my behalf. Here are the main issues arising for the PCS. If anyone want to comment/respond to these then please get in touch with me.

• It would be desirable to identify a "case designer" for AMMA on the soon side so that ties can be made to a land surface flux coordinator from GLASS/GABLS. The AMMA case could provide a project-oriented start to closer collaboration among the GEWEX groups (and land surface couping is too often neglected). Once an AMMA case designer/coordinator is identified, please contact Christian.
• It was asked whether there is a desire in the PCS working group to collect and rerun past cases, as the BL group is doing. This could be an element of the land-ocean convection theme emerging from the past cases. Please respond to me if you have any thoughts on this. My current take would be to see how the BL group get on and get feedback on how useful this has been to their group.
• Martin Miller suggested that the PCS group could make interesting use of Marat's high-resolution simulation results. The results aren't public at this point, but Steve Krueger agreed that interest could be solicited from the PCS group in advance if so desired.
• Regarding mid-level clouds, it was requested to bring more attention to the role of congestus in the TWP-ICE case (2nd week of the case study). This was pointedly requested in general response to the lack of (i) GCSS case study focus on mid-level clouds and (ii) a clear direction for how to address that. We may also want to place more emphasis on the mid-level clouds already present in existing case studies.
• Sandrine Boney requested that the PCS group consider two study areas that could shed important light on deep convection-climate relationships: (i) water isotopes and (ii) the tropical TOA balance of SW and LW cloud radiative forcing. Re water isotopes, Ann believes the CRYSTAL-FACE and TC4 experiments provided the type of field data that might provide a basis for case study analysis, and she believe the TC4 data may have indicated much more dilute but more frequent updraughts than during CRSYTAL-FACE; Re the TOA radiative balance, issues of time/area averaging were briefly discussed; namely, that the balance emerges over areas/times that are likely larger/longer than PCS case studies, which does not preclude studying how the case studies include related and perhaps very relevant information (e.g., about cloud structure, etc.).
• Re GEWEX 2009, themes are needed. A promising general theme is the cloud-precipitation-radiation cycle, for instance. Ideas should be sent to Christian and Pier.