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The 2001 GLASS panel meeting, Toulouse 7-9 November 2001
Participants : Aaron Boone, Paul Dirmeyer, Han Dolman, Paul Houser (over
phone), Randy Koster (over phone), Bart Nijseen, Taikan Oki, Andy
Pitman, Jan Polcher, Nicolas Viovy.
[14:00] Jan Polcher
- Confirmation of Agenda.
- Taikan Oki was appointed to take notes of the meeting.
[14:10] PILPS-2e by Bart Nijseen
- The aim of PILPS-2e is to evaluate land-surface
Parameterizations in Northern Regions. Preliminary results from the
PILPS-2e Model inter-comparison prepared by Laura Bowling, Dennis
Lettemaier, and Bart Nijseen were presented.
- PILPS-2e is the first step in a 3 stage process
- Stage 1: Torne/Kalix Rivers, 58 000 km2 Sweden/Finland
- Stage 2: (proposed) Mackenzie River, 1 800 000 km2
- Stage 3: (proposed) Lena River
- 21 models from 11 countries have participated in PILPS-2e.
- The 58 000 km2 basin of the Torne/Kalix rivers was modeled with
218 computational grid cells (0.25 degree grids) in this experiment.
- The meteorological forcing was provided at an hourly time step
over the 1979-1998 period. For spin-up the 1979-1998 period was used.
- Only 20 rain gauge stations are available over the basin and
thus there is a limit to the accuracy of the data. Precipitation was
gridded from SMHI station data. Lapsed for elevation and adjusted
for gauge under-catch per SMHI recommendations. Finally it was
statistically disaggregated to hourly data. A similar procedure was
applied for temperature, Pressure and relative humidity. Clouds were
derived from a 1 degree SMHI dataset. Wind speed was taken from
NCEP/NCAR reanalysis and finally long-wave radiation was estimated from air
temperature and the other variables.
- Original short-wave radiation was underestimated and corrected afterward.
- Moisture and energy balances were calculated to verify the
consistency of the data set.
- Using the annual mean latent and sensible heat fluxes the LSMs
can be divided into 4 groups.
- Some models have large sublimation fluxes which are compensated
by a negative sensible heat flux to maintain net radiation.
- For the mean annual turbulent fluxes the question was raised if
an error bar exists for observations.
- Simulated discharges were evaluated at the monthly time
scale. They reflect the large differences between models on the
simulated sublimation and snow melt. The runoff differences among
LSMs is highest in May, when the snow melt season starts.
- Different sensitivities for net radiation have been found. In May
it is controlled by albedo while in January is controlled by surface
radiative temperature (4.6W/m2/K).
- At high latitudes available net radiation rather than available
water is the limiting factor for latent heat.
- largest evaporation rates occur in the summer, but inter-model
variations in mean annual runoff are primarily related to the
model-predicted winter snow sublimation and melt.
- A participant's view on the value of the ALMA infrastructure was given :
- PILPS-2e participants were pleased with the ALMA variable definitions.
- Better documentation of the NetCDF interface on the ALMA web page is needed and
example of drivers for LSM should be provided.
- The ALMA web page should have an example scripts to covert
between NetCDF and ASCII for basic input/output.
- The programs that calculate the energy and water balance
errors need to be revised for different computer platforms and generalized.
- Organizer's view of ALMA:
- For many modeling groups this was their first exposure to NetCDF and thus a lot of help was needed.
- From a data processing point of view, a more strict respect of the convention for
describing coordinate axes and names is needed.
- Standard format that includes meta-data facilitates data
processing and quality checking.
- The question remained on the quality of the forcing data in the
region. But the community has little choice as the Torne/Kalix is the
region with the highest density of observations for the high latitude
- The group leading PILPS-2e was encouraged to investigate the
reasons in the design of LSMs which could explain the difference and
attempt more quantitative descriptions of the spread of results.
- The question was raised on the utilization of the hourly output
data? It seems that up to now only very little use has made of it.
- There is a need to archive the output datasets (or a subset of it) together with
the forcing data for future use and possible re-runs.
[15:38] Rhe-AGG by Aaron Boone
- Aaron Boone presented a quick overview of the project and the
workshop which was held in Toulouse early in the week.
- A classification of LSMs in terms of the treatment of surface and
subsurface heterogeneity was attempted to understand the results.
- All of the schemes successfully simulated snow in coarse
resolution for higher altitude where a lot of snow is present.
- The question was raised on the legitimacy of the comparison of
snow depth observations with LSM outputs, even at high resolution.
[16:40] Continue Rhe-AGG
- The panel suggested that a project overview in multi-author
paper on Rhe-AGG (BAMS or EOS are candidate journals).
- The ALMA data exchange format proved useful in this experiment
as well and allowed for an efficient quality check on the submitted
model output. This data set should be archived as well.
- An important issue for the Rhe-AGG forcing and validation data
of discharge, for instance, is to obtain permission to redistribute
- This discussion on the distribution of data related to past,
present and future experiments raised the issue of agreement from
model authors. GLASS needs to inform them about this intention and
ask for their agreement. We also need to reconstruct the data of past
experiments performed under PILPS.
[17:05] PILPS-C1 by Nicolas Viovy
- The aim, and the innovation this experiment will bring is to
compare land surface schemes with in-situ data for both water and
carbon fluxes .
- The PILPS-C1 experiment does not only target LSM representing
biophysical processes but also BGC models with crude representation
of biophysical processes, and models coupling biophysics and
biochemistry. This project is an opportunity to compare different
kinds of models so we would like to open the project to groups coming
from different communities.
- This project aims at a number scientific questions:
- What is the ability of the models to correctly reproduce both
biophysical and biogeochemical processes?
- Do models which include carbon out-perform those which do not?
- are the models able to reproduce the sink of carbon observed on
- The chosen site is Loobos in the Netherlands (one of the Euroflux sites).
- Three kinds of simulations will be proposed to the participants :
- A free simulations where only meteorological and soil
characteristics are provided to the participants.
- A constrained simulation where models are forced by
ancillary data which describe the vegetation (LAI, albedo, roughness, ...).
- A calibrated simulation where the possibility is given to calibrate
models using observed fluxes.
- How to organize this experiment ? Two options were discussed :
- Give all the data at the same time with the expectation that
groups will not use the ancillary and fluxes to calibrate models
for the free simulation.
- Give data in sequence but this solution is clearly more complex to organize.
- This experiment brings a new spin-up problem: carbon pools.
Especially the soil carbon needs hundreds of years to equilibrate unlike
the water reservoirs. In Loobos (like most other stations) the soil
carbon is not in equilibrium and an annual net sink is observed. Two
solutions are proposed and were discussed for this experiment :
The recommendation after discussion is to perform the 100 year
- Perform an equilibrium simulation using the first year of
data until equilibrium is reached. The model will then be
compared to the observed CO2 net flux-mean sink. This would suppress
any natural and observed long term trends.
- Perform a realistic 100 years simulation with forcing data
observed at a nearby meteorological station. This long data set
will not be of very good quality but probably good enough to
simulate the long term evolution of the vegetation.
- The participants will be asked to use the results of their 100
years run to initialize their carbon pools for the shorter
- The proposed analysis for PILPS-2e will be :
- monthly means
- daily means
- daily amplitude and phase of diurnal cycle
- analysis by weather types
- analysis of correlation and determination coefficient.
- Proposed time line
- November-December 2001: experimental details and forcing
- March 2002: submission of results for "free simulation"
- May 2002: submission of results for constrained simulations
- July 2002: workshop for analysis of preliminary results
Future PILPS experiments.
Finish at 18:00.
- There is a huge lack of PILPS experiments in semi-arid and
tropical climates and this should be the priority for the next
- During the discussion a number of sites were suggested but a
more detailed analysis of the feasibility for each of them needs to be
- The San-Pedro river basin in Arizona.
- The HAPEX-Sahel data from Niger.
- The OASIS observations in Australia.
[9:10] Some general information on the context of GLASS was given by Jan Polcher.
- The questions was raised yesterday on the link between GLASS and
SNOWMIP and especially the overlap of SNOWMIP and Rhe-AGG
experiments. SNOWMIP was launched by WGNE before GLASS was
set-up. Thus there is no formal link but interactions and communication exists.
- A short report was given on the WGNE/GMPP meeting which took
place the week before the GLASS science panel meeting. One of the
main points is that at next years WGNE/GMPP a effort should be made
to present to the forecasting community how GLASS can help them. In
particular which GLASS projects they should follow closely.
- Within GEWEX and GMPP there is a need to increase the
interaction between the various projects. For instance there is the
question from the GCSS on the table of how cloud models should deal
with land surface processes. Can we recommend one land-surface scheme
or any other procedure ?
- We need to raise the awareness that GLASS needs to have access
to an infrastructure which is able to collect GCM runs and
redistribute the data if we want to coordinate GCM experiments within
the global coupled action. An example for such an infrastructure is
AMIP. The need for such an activity will be raised at the GEWEX SSG.
[9:30] A short revisit of the PILPS-C1 discussion :
- The 100 year run for the spin-up of the carbon pools seems to be the best solution.
- In this experiment an opportunity should be given for any model,
even without vegetation dynamic, to participate, i.e. it should include DVGMs and SVATs.
- Announce this experiment in GEWEX and IGBP news letters, and to the US/European carbon communities.
- The schedule should start in January. 6 month are required
after the data is released for those who are not accustomed to
- This leads to a workshop in middle of May.
[10:00] Overview of PILPS.
- There is no prominent project in the waiting and we should use the
opportunity to push for a semi-arid experiment.
- The Murray-Darling river basin in Australian will probably
become a GEWEX CSE. This opens the possibility to do a Rhe-AGG
type experiment in the area after 2003. The idea could be submitted
to the Bureau of Meteorology.
[10:35] GSWP 1.5 presentation by Taikan Oki.
- The correction of catching ratio of raingauges for the
precipitation forcing of GSWP-1.5 was presented.
- Some applications of GSWP1 product were presented. For instance
the soil moisture was used as boundary condition for GCM experiments.
- Interesting applications of GSWP1 results for global water
resources assessment were presented.
- It was shown that projects are underway to assess the human
impact, such as irrigation, in land-surface scheme for an application
[11:40] GSWP-2 by Paul Dirmeyer.
- An outline of the GSWP-2 plan was presented and it's relation to
the evolution of the ISLSCP-II was discussed.
- GSWP-2 will present a challenge for the data management. To show
possible solutions a short introduction to DODS servers and their
potential was given.
- If all goes as planned with ISLSCP-II, the GSWP-2 could start at the end of 2002.
[12:25] Discussion of both GSWP experiments.
- Bill Rossow has proposed to provide upward long wave radiation
at the surface derived from satellite observations. This data could be
used to validate the land-surface schemes at the global scale.
- GSWP1.5 has to be seen as a preparation for GSWP-2. It should
allow us to put in place the infrastructure to handle all the data
which is needed for GSWP-2.
- The DODS technology should be testes with GSWP-1.5 so that it is
ready for use in GSWP-2. The same is true for the validation with
remote sensing data (upward long wave radiation at the surface).
- It is suggested that the models which produced carbon fluxes in
PILPS-C1 should do the same during the GSWP-1.5. This would enable to
compare the fluxes at the global scale.
- The questions was raised on the scientific objective of
GSWP2. It is proposed that a workshop will be organized in Autumn
2002, in conjunction with the next GLASS panel meeting, to decide on
these objectives. A few ideas were already suggested :
- The inter-annual variability of surface fluxes.
- Sensitivity tests of LSMs using 2 kinds of vegetation maps
and 3 kinds of forcing data. These will be available in the
ISLSCP-II data base.
- It is proposed that the output of the GSWP-2 experiment be
available for analysis by anybody who is interested.
- The data of GSWP-2 should be distributed widely through mirror DODS servers in a few places.
[14:10] Jan Polcher killing the time !
- The coupled local experiments were discussed. It is clear that
the priorities of this action need to be determined first and this
could best be done with a workshop. An ideal moment would be to hold
it together in March with the GABLE meeting.
- We quickly returned to the science plan for GSWP2. The other proposals which came up were :
- general impact of land surface on climate.
- inter-annual variation of soil moisture and fluxes.
- transferability of soil moisture from one model to another.
- waiting for Randy Koster on the phone ...
[14:50] Tele-conference with Randy Koster.
- The first presentation was about the Poor Man's land data assimilation experiments.
- The second presentation was the inter-comparison study which was
conducted with 4 models on the land-atmosphere feedback. This work is
currently being published in J. of Hydrometeorolgy.
- The question arose quickly if the Poor Man's LDAS should be
propose to AMIP as an experimental subproject. GLASS on it's own
would have difficulties to manage the data associated with such an
- The poor man's LDAS will be circulated among GEWEX/WGNE/AMIP in
order to evaluate the interest and to find help to organize this
- For the 2nd experiment a 2-3 page description of the project is
required and should be distributed widely within the community.
Groups are expected to start submitting their results in the middle
of the next year. Only a limited number of variables will be
collected in order to make the project manageable.
- In a final talk Randy Koster examined the standard PILPS
approach to inter-comparisons. It seems that it does not investigate
some important aspect of land surface models.
- The relations between E/Rn and soil moisture
or R/P and soil moisture as they are implemented in
land-surface scheme have been found to affect strongly the annual
energy and water budget and the seasonal memory of soil
moisture. They also impact the requirements for soil moisture
initialization for seasonal precipitation forecasts.
- It is proposed that a PILPS experiment be planed which not only
examines the reproduction of evaporation and runoff fluxes but also
the sensitivity of these fluxes to soil moisture variations. The
analysis would center on a comparison of this sensitivity (the fitted
slopes) to the sensitivity seen in the observational data.
- The requirements a site would need to fulfill for such
an experiment are first the usual PILPS measurements and secondly an
adequate measurement of both evaporation and soil moisture. One
possible study site could be the ARM-CART site in Oklahoma. The
PILPS-C1 site might also allow for such a study.
[16:40] Paul House came on the phone and discussed with those
present the local-coupled action.
- In this action a change in the coordinator will occur. Louis Bastidas will replace Hoshin Gupta.
- The LDASs looked very much like the GSWP experiment at
first. But this is shifting as more and more data assimilation starts
to be done in the LDASs.
- The local coupled action will concentrate on the interactions
between the atmosphere and the surface with a special attention to
the implications for data assimilation.
- It is proposed to organize a workshop at ECMWF in spring 2002 to
raise the awareness of the problems linked to the atmosphere/surface
interactions and try to propose some comparisons of methods for
forcing land-surface models which go beyond what is done today in
PILPS or GSWP.
- GABLES (The atmospheric planetary boundary layer project within
GMPP) held it's first meeting in August 2001.
- The major motivation for this project is to revive the
research on the PBL which had a declining activity after the
middle of the 1980s.
- David Randall initiated the project and it will be coordinated by Bert Holtslag.
- The first focus of GABLS will be to study the stable PBL.
- More than 20 groups participated enthusiastically at the
August meeting and it is expected that GABLS will be a very
[17:00] General discussion of the local/coupled action.
- The question was raised whether a similar experiment to Randy's
2nd proposal could be performed with meso-scale models and how that
could contribute to the understanding of the local coupling between
the surface and the atmosphere. Roni Avissar and Paul Dirmeyer
offered to explore the idea.
- The GCSS panel submitted to GLASS a request regarding their
handling of surface processes. For the moment they impose to their
cloud models estimates or measured surface fluxes and thus they freeze
any possible interaction between the atmosphere and surface. They are
thus asking what kind of standard surface model they should couple
to their cloud models. It should be the same for all models as they
wish to ensure a consistency between all models which will be
- The forcing of LSMs in cloud models is quite different from what
happens in GCMs. For instance the time step is 3--10 seconds and thus
the fast variations of fluxes can more easily be represented.
- The simplest proposal, and possible a good candidate, could be
the bucket model with an interception reservoir added.
- One solution would be to propose a simplified version of
CASM. But it would need to be fitted out with the PILPS4c interface.
- The best solution would probably be the improved bucket Chris Milly
has developed. A series of papers has been submitted by Chris Milly
which describes the value of each addition which was done to the
original bucket model. It is thus a very well documented simple LSM.
- There is no perfect LSM and thus no best solution for cloud
models. But what GCSS is looking for is a minimal LSM which represents
the major feedbacks in a physically reasonable way.
- VIC would also be a good candidate as it performs very well for
scaling through various resolutions.
- The point was raised that it could be ALMA's role to maintain a
standard simple LSM. This scheme would be useful to a number of
GLASS activities as it could be considered as the minimum requirement
for a LSM and other models could be evaluated by their added value.
[9:10] Revisit and continuation of the GMPP/GCSS request
- It was decided that Chris Milly would be asked if he accepts
that his model is considered as the "minimal reference" model.
- This activity of a "minimal reference" model should be part of
- Such a "minimal reference" model should be outfitted with the
PILPS4C coupler and an infrastructure which makes this model easy to
use. The PILPS4C interface is getting common in Europe, USA, and
Australia and ALMA should start coordinate these developments.
[9:40] CLIVAR monsoon panel has sent a request for GLASS to help
them in determining the role surface processes play in climate
- As the experiments proposed by Randy Koster will address this
issue we propose that he presents with Paul Dirmeyer the GLASS
activity at the CLIVAR monsoon panel. The next meeting of that panel
will be next summer in Texas.
- It appeared that the global coupled action will address these
issues and there is no need today to plan for anything more.
- Some actions on the validation of LSM in semi-arid conditions
could also help the CLIVAR monsoon issues. Thus the planed next PILPS
experiment should be linked up with the CLIVAR request.
- Would it be possible to do a PILPS experiment with the
GAME-tropic dataset ? This would be probably the best option to
evaluate the ability of our LSM to represent surface processes in
[10:00] The C4MIP project was briefly discussed.
- The GLASS panel needs to pay attention that a contact be
established between PILPS-C1 and C4MIP. PILPS-C1 can be viewed as the
point validation for the LSM used in C4MIP.
- Peter Cox or somebody from the Hadley Centre should be on the
GLASS panel to represent the C4MIP project and ensure that the
contact is maintained.
[10:40] The ALMA action.
- There is a need to update the data convention after the
experience gained in PILSP-2e and Rhe-AGG. Comments from Aaron
Boone will be integrated. Help needs to be provided for data
preparation for those organizing experiments. This could be done by
providing examples. Some of the documents need to be corrected.
- The list of output variables needs to be expanded so that it
include the requirements of the PILPS-C1 experiment.
- Jan Polcher will take care of updating the convention.
- The names used for the axis by the groups sending in data
should be standardized. The meta-data convention ALMA uses caters
for that but there is a need to make sure that the participants
are aware of this and use it.
- There is a need for a simplified description of the data
exchange convention. A simple "How To" could be useful.
- ALMA needs to keep an archive of previous experiments.
- All PILPS experiments should be archived in the ALMA format.
This will require some digging to find some of the data sets. It
is essential to have the forcing data, the verification data is
important and it would be very nice to have the output of all
- There is a need to include in the forcing data files a
description of the reference level at which wind, humidity and
temperature have been measured. This would allow model to adapt
to this automatically.
- The ISLSCP-I data is archived at IIS/UT (Tokyo). It is
archived in the standard ALMA format and a number of problems
have been identified or corrected :
The full dataset should be ready before Spring, 2002 for GSWP1.5 as well as for GSWP2.
- long wave correction
- land/sea mask in Canada should be corrected.
- For the PILPS 2e and Rhe-AGG experiments the panel needs
to ask permission for archiving and distributing the results from
- DODS servers should be operated at COLA and IIS/UT for GSWP2.
- This should be started with PILPS2e forcing data.
- The forcing data server should be ready in Spring 2002.
- The output variables from GSWP-1.5 amd GSWP-2 should be
consistent with the ALMA data exchange format.
- This activity is essential in the preparation for the GSWP2 experiment.
[11:20] Discussion of the implementation Plan.
- The executive summary of the implementation should be published in BAMS or EOS.
- First the last version of the implementation plan (November
2000) needs to be verified and updated.
- How will the executive summary be prepared ? Andy Pitman will edit the
implementation plan for such an article.
- The improvements of ALMA with the introduction of DODS needs to
be described in the implementation plan.
- For those GLASS panel members who need to have the support of
their home institution to ensure their participation in meetings, a
letter from David Carson (WCRP director) can be arranged.
- Paul Houser and Bart van den Hurk will organize the workshop of
the local coupled action in spring 2002.
[12:05] Review of the action items (see below)
Finish at 12:30.
Actions decided during the 2001 GLASS panel meeting
| PILPS-C1 : The experimental plan needs to be finalized in
accordance with the recommendations of the panel.
|| Nicolas Viovy
| What are the options for a PILPS exercise in a semi-arid or an
|| Bart Nijseen
| A letter needs to be sent to PILPS-2e and Rhe-AGG
experiments to ask if they accept that their model output is
archives by ALMA.
|| Jan Polcher
| GSWP1.5 will be organized and two objectives are set : 1) it
should prepare the infrastructure for GSWP 2 2) it should pave the
way for the validation of LSM (land surface model) with remote
sensed data. An experimental plan will be submitted to the GLASS
panel before the end of the year 2001.
|| Taikan Oki
| GSWP 2 will prepare its experimental plan and work with GSWP
1.5 for preparing the infrastructure. A workshop will be held at
the end of 2002 to finalize the GSWP 2 experimental plan.
|| Paul Dirmeyer
| The more academic experiment (labeled exp2 during the meeting
and described in a recent paper by Koster et al.) with GCMs
proposed in the global coupled action should start soon. An
experimental plan should be finalized and distributed.
|| Randy Koster
| We need to prepare the poor man's LDAS experiment proposed in
the global coupled action on a broader basis. It is of more general
interest that just the LSM community and it should be carried out
in close collaboration with GSWP and AMIP.
|| Randy Koster, Jan Polcher
| Activities in the local coupled action need to be launched
with a workshop in the spring of next year. The aim of the workshop
will be to review current activities in the field and recommend an
experimental set-up for models which can be used to test the
surface atmosphere interactions.
|| Paul Houser and Bart Van den Hurk.
| What can be done to test surface/atmosphere interactions with regional models ?
| We need to contact Chris Milly to see if his new model, the
description of which is currently being published, could serve as
a baseline model for the community and be recommended to GCSS and
other GMPP projects.
||Jan Polcher, Andy Pitman and Paul Dirmeyer
| Is there a possibility that GAME-tropic has produced data
which could be used for a PILPS type experiment ?
| We have to take up contact with Peter Cox to see how best
C4MIP an be represented on the GLASS panel and how the link with
GAIM/IGBP can be maintained. In view of the expertise available at
the Hadley Centre somebody from the Haldey Centre should be on the
| Version 3 of the ALMA data exchange convention needs to be
written. This is only an incremental change from version 2 and
corrects bugs found and enhancements needed for PILPS-C1.
|Forcing data from previous experiments need to be assembled in
one central location. In some cases the data needs to be tracked
down. This effort will be followed later by the output data from
the inter-comparisons since PILPS-2e.
||Taikan Oki with help from Andy Pitman
|A convention is also needed for the ancillary data used by
land-surface schemes in the various inter-comparison. This effort
should be done in collaboration with ISLSCP.
|| Paul Dirmeyer
| The implementation plan needs to be finalized in some way. The
proposal is to read through it correct it where needed and put it
on the web. It will not have the quality of a printed document but
will nevertheless constitute an important description of
GLASS. Then it will be thinned out to make it suitable for
publication in an appropriate journal.
||Jan Polcher and Andy Pitman
| Minutes of 2001 GLASS panel meeting.
| Next GLASS panel meeting at COLA.
Feedback to Taikan Oki
email@example.com) will be highly appreciated.
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