6 Sept 2010
Outcome and prospects from the August 2010 panGEWEX and SSG meetings, Seattle.
Kevin E Trenberth
GEWEX held a “pan-GEWEX” meeting in Seattle for a week in late August 2010. The “pan-GEWEX”
connotation means that it was an opportunity for all of the working groups and panels within GEWEX tomeet together and exchange views while interacting to formulate future plans. Accordingly, the
Scientific Steering Group (SSG) attended and participated fully, and we took the opportunity to have an
SSG meeting after the full meeting closed. In addition, a number of program managers from different
nations attended, and we were fortunate to be able to involve a number of young scientists in theprocess (see report elsewhere).
This pan-GEWEX meeting was especially eventful owing to a number of challenges before thecommunity in formulating plans for the new post-2013 phase of the WCRP, guided by the JSC. In
particular, the guidance suggested that core projects would be retained but with revised responsibilities
to facilitate climate system research at the interface of the physical Earth system components. The
suggested four new core projects should be: 1) Ocean-atmosphere (think CLIVAR); 2) Land-atmosphere(think GEWEX); 3) Cryosphere (think CliC); and 4) Stratosphere-troposphere (think SPARC). Then withineach core project there should be a common set of basic “themes” including 1) Observations andanalysis; 2) Model development, evaluation and experiments; 3) Processes and understanding; 4)Applications and services; and 5) Capacity building. Coordination across projects on these themes would
be via WCRP Modeling and Observations Councils.
In preparation for the forthcoming changes, prior to the last JSC meeting, the GEWEX SSG met in
January 2010 in New Delhi and began formulating plans for the future via a new mission statement, a
set of imperatives (things that must be done), and a set of frontier challenges for the future. The draft
set of these was published in the May 2010 GEWEX newsletter as a basis for the pan-GEWEX
discussions.
At the January meeting, I had challenged the SSG to say why the three GEWEX panels: Radiation (GRP),
Modeling (GMPP), and CEOP should be together. The arguments were strong and convinced me that weshould continue with similar components in any future GEWEX. Figure 1 illustrates the points from thestandpoint of the hydrological cycle, featuring radiation, atmospheric processes and land surfacehydrology and processes. The original motivation for these being together is that they correspond to the“fast” processes in the climate system, and this still applies. Following the JSC meeting in February, key
questions were “how much science falls under land-atmosphere” and “what about those that do not?”Accordingly, the approach taken in the pan-GEWEX meeting was that while the future GEWEX should
indeed be the place where land-atmosphere interactions were featured, it should be much more. In
particular, it should retain the global energy and water cycle as a core focus while adding regional
aspects. It should indeed also feature hydrological and land surface processes and modeling, andinteractions with the atmosphere. However, it should further retain a strong atmospheric component
related to the water and energy cycles, and hence scientific issues related to radiation, clouds,
convection, precipitation, boundary layers, surface fluxes, runoff, and human influences which should
also be included in terms of observations, process understanding and modeling.

Fig. 1 depicts the hydrological cycle schematically and thus the driving by radiation and energy, theatmospheric dynamics that move water and energy around and produce clouds which block the sun, thecomplex land surface complete with human influences and the interactions with the atmosphere, andthe surface and below surface processes that complete the water cycle (adapted from Trenberth et al.
2007).
The meeting provided a venue for vigorous discussions of the draft imperatives and the future directions
for GEWEX. Following the meeting, the SSG has decided on the following. 1) While the old GEWEX namewas liked by many for its uniqueness (e.g., in a google search) and name recognition, no-one has comeup with a viable alternative for the “EX” part that is clearly obsolete. Accordingly, the new name post2013 is suggested to be: “Global and Regional Energy and Water” (GREW). This has many aspects incommon with the old name and the two should be used together for a period of time. The revised
mission statement is:
To measure and predict global and regional energy and water variations, trends, and extremes (suchas heat waves, floods and droughts), through improved observations and modeling of land,
atmosphere and their interactions; thereby providing the scientific underpinnings of climate services.
There were strong sentiments for fewer more succinct imperatives, and the following seven have been
approved by the SSG:
Datasets: Foster development of climate data records of atmosphere, water, land, and energy-related
quantities, including metadata and uncertainty estimates.
Analysis: Describe and analyze observed variations, trends and extremes (such as heat waves, floods
and droughts) in water and energy-related quantities.
Processes: Develop approaches to improve process-level understanding of energy and water cycles insupport of improved land and atmosphere models.

Modeling: Improve global and regional simulations and predictions of precipitation, clouds, and landhydrology, and thus the entire climate system, through accelerated development of models of theland and atmosphere.
Applications: Attribute causes of variability, trends and extremes, and determine the predictability ofenergy and water cycles on global and regional bases in collaboration with the wider WCRP
community.
Technology transfer: Develop diagnostic tools and methods, new observations, models, data
management, and other research products for multiple uses and transition to operational applications
in partnership with climate and hydro-meteorological service providers.
Capacity building: Promote and foster capacity building through training of scientists and outreach tothe user community.
The header in each case highlights the link between the imperative and the themes outlined by the JSC.
There is still much to be done to flesh out these imperatives with more details about what they mean interms of the actions to be taken, the lead groups in GEWEX and interactions with other parts of WCRP,
and the other organizations involved.
Modeling
Prior to the pan-GEWEX meeting, extensive discussions had been held by email that set the stage for the
discussions in Seattle. These arose in particular from a desire for the chair of GMPP (Christian Jakob) tostep down and a proposal to remove the layer of GMPP, as well as the need to address the future
structure of GEWEX and GEWEX modeling post-2013. The many questions and statements that arose
were summarized as a series of questions, mostly related to modeling, that were appended to the panGEWEX meeting agenda. Based on those discussions, I offered some proposals for how this may move
forward that turn out to be similar to those adopted.
The proposal of removing the GMPP layer between GCSS, GABLS and GLASS with the SSG met withstrong approval. Instead GCSS/GABLS will be combined and, along with GLASS, will report to and takeadvice from the SSG directly. This proposal was subsequently approved by the SSG.
As a consequence of the removal of the GMPP layer there is a need for GCSS/GABLS to undergo somereorganization. This will also pave the way for the post-2013 transition. As a result of the discussions it
was proposed that GCSS abandons its current Working Group structure. Instead, the group will operate
through projects. Those can be initiated by any member of the community. A Science Steering
Committee (SSC), which will form the GCSS/GABLS Panel, will be responsible for the successful runningof the program. This includes the approval of proposals as well as engagement with the community to
explore new opportunities. The GABLS activities will be fully integrated into this structure through
GABLS-specific projects as well as GABLS membership on the SSC. The GCSS and GABLS brand names will
be maintained. This proposal was also subsequently approved by the SSG.
Most of the discussion in the group was about the extension of the current atmospheric model
development activities in the post-2013 structure. This resulted in the proposal for a Framework for
Atmospheric Model Enhancement (FAME). The mission of FAME is proposed as: Improving therepresentation of physical and dynamical processes in the troposphere in models for all purposes andespecially weather and climate services. Its main focus would be the improvement of the representation

of clouds and precipitation in atmospheric models, which can only be achieved by improving ourunderstanding of the intricate coupling of physical and dynamical processes associated with clouds andprecipitation at various scales.
FAME was proposed in recognition of need expressed by the IPCC in several reports which highlighted
the significant shortcomings in models in the simulation of clouds and precipitation with consequences
for the simulation of important climate feedbacks and climate sensitivity. Other important factors
included the recent revolution in the ability to observe clouds and precipitation, especially from space,and improvements in ability to model the processes involved at the process-scale. The experience ofmore than 15 years of the GCSS program and almost 10 years of the GABLS program makes the timeright for a more concerted effort in atmospheric model improvement that builds on the existing
strengths and adds to them the important new research area of physics-dynamics coupling.
The envisaged ingredients of FAME would be programs on the PBL (GABLS), clouds, convection andprecipitation (GCSS), radiation (currently residing in GRP and SPARC), coupling to dynamical processes(new) and potentially also coupling to numerics (new). FAME will be built around the core approaches
identified by the WCRP JSC, e.g., observations, modeling, data analysis and model diagnosis, and process
studies. Through the direct involvement of operational modeling centers in FAME as well as through theengagement of scientists throughout the world, the activities in FAME will make major contributions tocapacity building and services.
As FAME is tightly focused on providing a means for the improvement of the representation of core
physical processes in atmospheric models, it will partner with many other programs to contribute to theresearch on phenomena that go beyond the physics-dynamics coupling in the atmosphere. Those
include partnerships with the land (e.g., GLASS, GHP), ocean (e.g., CLIVAR), aerosol (e.g., ACPC, iLEAPS),
atmospheric chemistry (e.g., SPARC, IGAC), stratosphere (e.g., SPARC), and cryosphere (e.g., CliC)
communities. Necessarily, these go well beyond GEWEX alone.
FAME could be seen as a natural extension to the existing GCSS/GABLS panel described above, if the
post-2013 GEWEX structure still allows for such an activity. This would maintain continuity, provide close
links to the land and limited area modeling communities and ensure FAME’s natural focus on the energy
and water cycles. These activities were originally grouped together to provide a focus on relatively “fastprocesses” as compared with those involving the ocean or cryosphere. FAME could also make a major
contribution to a potential cross-WCRP effort on atmospheric model development.
This proposal was subsequently discussed by the SSG who strongly recommend keeping FAME within
the post-2013 GEWEX structure. Questions include how FAME goes forward, whether as a panel orworking group. Many of the other modeling activities in WCRP come under working groups. WGSIP isan example where the WG reports to the CLIVAR SSG but acts on behalf of the WCRP to deal withseasonal to interannual prediction. A new group, integrating FAME and possibly called WGAP, short for
WG on Atmospheric Processes and modeling for climate, could operate similarly within the new post2013 GEWEX. However, as the activities relate to the established WGs, especially WGNE, this aspect is
yet to be decided after broad consultation with the community.

Land surface and hydrological science
Major changes were also underway in the realm of the regional hydrological projects at the pan-GEWEX
meeting. In part these came about naturally from the evolution of the program, and given extra nudge
by the change in leadership. Under the leadership of Toshio Koike, CEOP developed an impressive andextensive program, including the Regional Hydrometeorological Programs (RHPs), associated modelingand data base development, and the Hydrologic Applications Project (HAP). CEOP remains at the core of
the GEWEX mission, includes more than a thousand researchers, and provides important regional data,
modeling and a valuable end-user interface.
The brief history is that the Continental Scale Experiment (CSE) concept was developed in the 1990s. Its
purpose was the development, diagnosis, and testing of coupled land-atmosphere models with a focus
on water and energy budget closure at near-continental scales. An example was the GEWEX Continental
Scale International Project (GCIP) for the Mississippi basin as a well instrumented and analyzed region.
This led in turn to the development of RHPs to extend this concept to other regions: MAGS, BALTEX,
GAME, LBA, AMMA; and even more recent RHPs, see Figure 2. The panel set up to provide coordinationand oversight was the GEWEX Hydrometeorological Panel (GHP). Then to take advantage of many newsatellite and other observations the Coordinated Enhanced Observing Period (CEOP) was begun in 1995
and continued into the second phase of GEWEX for 2001-2006. This activity, which also developed
extensive data management activities, led by Toshio Koike in Japan, also led to some similar panels to
those in GHP and some duplication of effort. Accordingly, this first CEOP activity was combined withGHP and evolved to become the Coordinated Energy and Water Cycle Observations Project with thesame acronym, CEOP, in 2007-2008. The initial observing period grew to become a move to produce a
10 year dataset and archive especially set up for the regional projects. However, other developments
had already occurred in observations and data management, which suggested the activity should be
wrapped up and refocused, even as it is utilized and hopefully becomes part of the heritage of GEWEX.
In particular, the development of the many flux towers around the globe provide alternatives to the
CEOP reference sites for local studies of energy, water and biogeochemistry.
Accordingly, the community began what might be called a “back to basics” movement, with recognitionof the need to reinvigorate the regional hydrological projects. In particular there was a call by the new
co-chair, Dennis Lettenmaeir, for stronger hydrological activities which would foster the next generationof hydrologically realistic land surface schemes and provide a home for projects like PILPS. The
recommendation to the SSG was along these lines and thus a new GEWEX Hydroclimatology Panel(GHP: note the change in the name from the first version) has been formed to replace CEOP, effective
immediately. The SSG also followed up on the recommendation from CEOP to approve a new RHP
called the HYdrological cycle in the Mediterranean Experiment (HyMeX), focused on the 20 countries
around the Mediterranean Sea and the fresh water and salinity of the Sea itself.
GHP is thus the home for hydrologic science and modeling within WCRP and there is considerable scopefor developments in this area, e.g. in seasonal forecasting, the detection and attribution of change, andthe development and analysis of climate projections. Challenges remain in dealing with monsoons andto help coordinate the multitude of national initiatives in this area. There are also opportunities forlinkage with GLASS in bringing disciplines together in the development of next generation Land Surface
Models as well as increasing interactions with CORDEX. Changes in the management structure are likely
to accompany the new consolidation of efforts as GHP realizes its considerable potential.

Fig. 2: The GEWEX RHPs as of 2008(??).
GEWEX Datasets
The original GEWEX datasets were developed under the auspices of the GEWEX Radiation Panel (GRP)
which continues, but is also looking for a name change as it does a lot more than radiation. It does deal
with all of the global satellite data related to energy and water and their synthesis into products, and iscurrently leading and promoting reprocessing of the datasets with a goal of creating climate data
records of sufficient quality to be useful for examining trends. Some of the datasets, such as GPCP and
ISCCP, are well known and already used extensively, but the scientists are confident that they can bemade much better and more consistent with each other, and with better estimates of uncertainties.
In general GRP is working well toward the new goals and has produced simulators, that take into
account the sampling and characteristics (such as thresholds) of the observations to enableintercomparisons of satellite products with model data. Interactions with other parts of GEWEX were
fostered by the pan-GEWEX meeting, and the GEWEX datasets have potential for great use in evaluating
and improving models on issues such as clouds and indirect effects of aerosols, precipitation frequency,
intensity and amount, and in providing the context for the RHPs.
Extremes
The recent summer record breaking flooding in Pakistan, India and China, and heat-waves and wildfiresin Russia highlight the extremes of the hydrological cycle of drought and floods that are changing fromhuman activities. Dealing with extremes in WCRP is a cross-cutting activity that involves all projects
although GEWEX plays a leading role. Olga Zolina, who is a member of the GEWEX SSG, led the WCRP
extremes workshop involving some 150 people at UNESCO in late September. Breakout groups were
held on issues of 1) data requirements and availability (such as the need for hourly precipitation data toproperly characterize extremes); 2) representation of extremes in models, including scaling and spatial
issues (how station data relate to grid squares, comparing apples to apples); and 3) methodologies forestimating extremes across areas and disciplines, including statistical methods. Continuing issues are
sorting out the human changes in extremes and how to best communicate with the general public onsuch technical attribution issues.
For instance, it is likely that the southeast Asian floods and the Russian drought were linked by themonsoonal circulation and teleconnections linked to the anomalous latent heating of the atmosphereassociated with the heavy rains. The pattern of the rains was related to the rapidly developing La Niña
but the previous El Niño had left behind a residue of abnormally high sea surface temperatures in theIndonesian-northern Indian Ocean region that provided an enhanced supply of moisture to themonsoon rains. No doubt those elevated temperatures have a global warming component. The
persistent “blocking high” over Russia led to drought that was no doubt more intense and longer lasting
owing to global warming, with increased risk of heat waves and wild fires. While these connections arevery likely, they are hard to prove as models do not reproduce monsoon rains very well, and blocking ispoorly simulated. These scientific challenges extend across the WCRP.
Closing remarks
The above is but a sample of the goings on and developments from the pan-GEWEX meeting. What I
have tried to do is provide a sense that we are looking forward to the future with considerable
excitement at the science we can achieve through collaboration and friendly competition, with the helpof coordination through GEWEX and, in the future, GREW. I would like to thank all of those who
attended and participated.