2005 Meeting of the GEWEX Radiation Panel
The 16th session of the GEWEX Radiation Panel (see http://grp.giss.nasa.gov for links to
all projects mentioned) was held at the Observatoire de Paris on 3-6 October 2005 and included a
viewing of a nearly-total eclipse of the sun during the coffee break on the first day. Two new
members joined GRP at this meeting: Norm Loeb (NASA Langley Research Center) and Luiz
Machado (CPTEC, INPE). Key goals for this meeting were to review and evaluate global data
collection and analysis activities relevant to GEWEX objectives, review on-going study
activities and plan new initiatives concerning remote sensing of atmospheric water vapor, ocean
and land surfaces, precipitation and aerosols.
Monday morning, 3 October: The meeting began with an Executive Session to review
meeting goals and identify specific topics and possible initiatives to be discussed. Key topics
were: (1) formulating best practices to produce Climate Data Records, (2) identifying future
activities in radiation and precipitation, (3) considering plans for a joint data product re-processing activity to develop recommendations for WGDMA, and (4) reviewing the overall
GRP Plan in the context of on-going global data projects, working groups and study projects.
Possible new initiatives to be considered were: (1) a re-activated GVAP, (2) the next phase of
ISLSCP within the LandFlux initiative and (3) aerosol activities.
A summary of WCRP activities focused on the on-going development of the COPES
infrastructure, particularly discussions occurring at the first meeting of the WCRP Observation
and Assimilation Panel (WOAP) at which GRP represents GEWEX. Three topics suggested by
GRP have been taken up by WOAP: working to unify data policies across WCRP projects,
continuing communications of WCRP needs to the satellite-operating agencies to foster a
cooperative approach to calibration of the whole satellite constellation and proposing a
coordinated re-processing of global, long-term data products. GRP was also asked to provide
comments on the recently released GCOS Implementation Plan and the soon-to-be-released
GEO Work Plan. A draft of the GEWEX “roadmap” – a set of specific milestones to be reached
to achieve the recently revised GEWEX objectives – was presented with the request that GRP
provide milestones representing its activities.
Representatives from ESA, INPE, JAXA, NOAA and EUMETSAT presented updates on
their spacecraft missions and plans. Relevant highlights of ESA missions include scheduled
launches of CryoSat in 2005 (a sea ice and ice sheet mission that was lost in a launch failure on 8
October), GOCE in 2006 (a follow-on to GRACE), SMOS in 2007 (a ocean surface salinity and
land surface moisture mission) and ADM-Aeolus in 2008 (a Doppler lidar mission to measure
wind and aerosol profiles). EarthCare, a multi-instrument mission featuring a cloud-aerosol
radar-lidar combination in partnership with JAXA, has been approved for launch in 2012. Other
missions are being planned under the GMES Sentinels program but support for the European
contribution to GPM seems ill-defined. For the first time, the Brazilian space agency, INPE,
provided an overview of its programs. Highlights include continuation of a joint Brazil-China
land remote sensing satellite series (CBERS, seven “visible” channels from 0.45-0.89 :m, three
near-IR channels from 0.5-2.35 :m and a “window” IR channel at 10.4-12.5 :m), developing a
new line of applications satellites (SSR), launch in 2007 of a GPS atmospheric profiling mission
and a proposal for a low-inclination (tropical) orbiter to supplement the GPM constellation.
Discussions are also underway to develop a geostationary weather satellite capability, possibly
beginning with operating one of the spare US GOES satellites. JAXA is focusing its efforts on
the continuation of TRMM (see below) and the launch of ALOS in 2006 (a land remote sensing
mission) and GOSAT in 2007 (a atmospheric composition mission). However, JAXA is also a
major partner both in GPM in partnership with the US, providing the precipitation radar core
satellite, and in EarthCare in partnership with ESA. Also under discussion is a proposal to start a
series of missions (GCOM) to provide follow-up flights for specific ADEOS instruments,
AMSR in 2010 and GLI in 2011.
Monday afternoon, 3 October: The NOAA operational satellite constellation is in good
condition with two healthy primary polar orbiters (with two mostly healthy backups) and two
healthy primary geostationary orbiters (with two healthy backups, one on loan to the Japanese).
The next “morning” polar orbiter, METOP-A, will be launched next year by EUMETSAT and
GOES-N will be launched later this year. The launch of the last polar orbiter, NOAA-N’ (newly
refurbished) is planned for the end of 2007; but launch delays for NPOESS appear likely,
making launch of NPP into an “afternoon” orbit seem necessary. NOAA continues expansion of
its web-based data dissemination system and formulation of the characteristics of Climate Data
Records. The EUMETSAT operational constellation is in good shape with METEOSAT-7 and 8
near 0E and METEOSAT-5 at 63EE. If the MSG-2 launch at the end of this year is successful,
METEOSAT-7 will be moved to replace METEOSAT-5. With the launch of METEOP-A next
year, EUMETSAT will accomplish a major expansion of its constellation to include a polar
orbiting satellite in the “morning” orbit. Also highlighted were plans to launch the follow-up
ocean altimeter mission, Jason-2, in 2008.
The EUMETSAT representative led a discussion about cross-calibration of the radiances
measured by the operational weather satellites, presenting results from an activity at
EUMETSAT to refine the calibrations for the METEOSAT series. There were also two recent
activities fostered by CGMS for the primary visible and infrared radiances. NOAA activities to
inter-calibrate the AVHRR instruments were also described. Combining these results with those
from ISCCP to cross-calibrate all the meteorological satellites provides the prototype of an
international cooperative system for a common set of calibrations. The WMO Space Office also
sponsored a workshop this past summer on this topic. All of these activities and discussions
suggested that GRP (and WOAP) should renew its endorsement to CEOS of the ideas of
organized cooperation to maintain a common calibration for the operational satellite
constellation and, further, that the operational agencies work towards development of a joint in-space calibration satellite.
EUMETSAT has organized a number of Satellite Application Facilities (SAF), consortia
of universities and government institutions that are responsible for producing data products from
satellite measurements. One of these, the Climate Monitoring SAF (CM-SAF), is responsible for
producing climate data records useful more monitoring climate variations with a focus on the
near-European region. Currently in Phase 2, the CM-SAF is producing products from AVHRR
and SEVIRI/GERB on MSG (clouds, top-of-atmosphere and surface radiative fluxes) and
assembling a global composite water vapor product (Humidity Composite Product) from
measurements by several infrared and microwave sensors. Phase 3 is expected to begin in 2007
with expansion of the area and time period covered and addition of new products.
The Geostationary Earth Radiation Budget instrument on METEOSAT-8 (MSG-1) is
providing the first high time resolution (15 minutes) top-of-atmosphere radiative flux
determinations. This first look at the detailed behavior, especially diurnal variations, of radiative
fluxes already shows subtle and interesting features that modulate the energy exchanges within
the surface-atmosphere-space system (e.g., time lags in variations of longwave fluxes and
“unexpected” asymmetries of the clear sky albedo over ocean with respect to the sun).
The report on the status of the CERES project began with a summary of reconstructions
of anomalies in the top-of-atmosphere radiative fluxes: the long-term changes inferred from the
ERBS instrument are in close agreement with other shorter-term scanner measurements from
several missions, with two sets of calculated fluxes based on the ISCCP cloud products and with
inferred changes in the ocean heat content from satellite and buoy measurements. Most notable
is that the advanced radiative flux products using angle dependence models derived from conical
scanning measurements are now being released (edition 2 for Terra is available covering 5
years); edition 3 processing is expected to commence next year.
A brief report provided very welcome news that NASA and JAXA have approved the
continuation of the TRMM mission, using the available on-board fuel for maintaining orbit
rather than for a controlled atmospheric re-entry. Given the current phase of the solar cycle and
the available fuel, TRMM may be able to last until early next decade when GPM is to be
launched. This fact also means that, if the launch of CloudSat/Calipso later this year is
successful, there will be two radars in orbit for a few years that, together, may provide a more
direct global precipitation product (as the CloudSat radar is sensitive to light rain and snow) with
vertical structure information for both clouds and the precipitation they produce.
Tuesday morning, 4 October: Norm Loeb (new GRP member) presented some of his
research on improved angle dependence models now being used in the analysis of the CERES
observations to produce more accurate top-of-atmosphere radiative fluxes. The two major
advancements are use of the conically scanning instruments on TERRA and AQUA to collect
much more extensive and detailed statistics of the angular variation of the broadband radiances
and the use of imaging radiometer measurements on the same platforms to categorize the scene
by both surface and cloud properties and sort the angle dependence by these properties. Not only
does this approach reduce the flux uncertainties associated with angle dependence to less than
4% rms, but the resulting products are much more reliable when used to characterize the fluxes
for different kinds of clouds and for clear sky with varying aerosol burdens.
The Surface Radiation Budget project is its 20th year; by the end of this year, all products
will be available for a period covering 1983-2001. The supporting web site for accessing these
products has been newly revamped to provide more options and information. Project funding is
approved through next year which will allow for product processing to be extended through
2004, providing overlap with CERES products. However, because two different sources of
atmospheric temperature and humidity had to be used, the entire product will be re-processed in
2006 using a single source of atmospheric information. Comparisons of downwelling fluxes
from SRB and BSRN (as well as the GEBA archive), show shortwave/longwave biases < 10 / <
5 Wm!2 and rms differences of about 25/15 Wm!2 for monthly mean values. As evaluations
continue, improvements have already been identified: for the shortwave, refined aerosol and
surface albedo climatologies can be implemented along with use of the latest CERES angle
dependence models; for the longwave, improved estimates of cloud base locations (possibly
from CloudSat/Calipso analysis) and better treatment of the near-surface atmospheric and
surface skin temperatures.
The Baseline Surface Radiation Network is in its 11th year and now is composed of 38
sites (with 12 provisional sites) collecting the full set of radiative flux and meteorological
measurements. BSRN has completed its first full year as the radiation reference network for
GCOS. Discussions are underway to include some SkyNet sites within BSRN. In the past year a
“diffuse” closure study was completed and workshop was held to develop ways to obtain BSRN-quality radiative fluxes over oceans. Proposed expansions of the measurements being considered
include aerosol and cloud properties (the former using new instrumentation, the latter analyzing
the radiative fluxes themselves), spectral measurements and adding surface turbulent fluxes to
provide a complete surface energy budget. The BSRN Archives improved data access by making
software available for reading the ftp data products. Funding for the sites appears to be adequate
but the Archives are not able to expand to include new products and their future is currently
uncertain.
The Radiation Products Assessment held its first workshop in Zurich in October 2004
and is planning its second workshop in Virginia, possibly as early as February 2006. A detailed
outline of the study report has been completed to guide work. A web site to support the work by
providing access to the main data products is also now operational. The basic comparisons of
ERBE, early CERES, BSRN, GEBA with SRB and ISCCP-FD have been completed: such basic
comparisons indicate excellent agreement on average, with the largest differences occurring in
surface longwave fluxes. However, more detailed examinations of all of these products show
subtle differences that are still significant to the uses of these products. Two examples from a
comparison of the SRB and ISCCP-FD products was presented in an invited talk by Ehrhard
Raschke. He showed how different even the determination of the top-of-atmosphere solar
insolation can be because of various approximations or short-cuts sometimes adopted,
particularly in current GCMs. He also showed that the long-term variations of longwave fluxes
at the ground differ because of different representations of the variations of atmospheric and
surface temperatures. Once the main data products are made available on the web site,
researchers will be recruited to investigate various differences among the datasets. The plan is to
complete the assessment and report by early 2007.
An invited presentation by Sandrine Bony presented more results from “dynamic
compositing” estimates of cloud-radiative feedbacks on climate. This approach composites the
observed variations of clouds and radiation in different dynamic regimes and then considers the
consequences of variations of the atmospheric circulation with climate change. Climate change
experiments with current-day models suggest that the differences in their sensitivity are
associated with difference in their treatment of the variety of tropical clouds, particularly low-level clouds. Comparisons of observed interannual variations of these cloud types and dynamical
regimes to models show that they do not currently represent the interannual variability well.
A presentation by Luiz Machado (new GRP member) reviewed what has been learned
about the distribution of water vapor in the tropical upper troposphere and the organization and
behavior of tropical convective systems from a combination of field experiments and satellite
observations. Field experiments in Brazil comparing various in situ and remote sensing
measurements of humidity show the largest disagreements in the upper troposphere (although
the different radiosondes also disagree near the surface as well), but the newer microwave
sounder and GPS-based methods appear to agree better. Satellite observations of convective
organization have established quantitative relationships between the size and lifetime of
organized systems; especially important is that the initial areal expansion rate of these systems
appears to be closely related to the divergence and mass flux in these systems. These studies also
reveal a much more complex behavior comprising the diurnal and seasonal cycles of convection.
These details can now be compared with models to refine their treatment of this key process.
Tuesday afternoon, 4 October: A special presentation by John Bates from NOAA
discussed the characteristics of Climate Data Records, particularly those characteristics that
indicate how mature a research or operational product is and whether it is ready to be
transformed into a reference climate record. For example, a product could be judged according
to criteria measuring its scientific maturity, how easily accessed and how well preserved the
product is, and how much impact the product has. The discussion that followed also mentioned
the need to define the procedure for transitioning research analysis activities into operational
ones so that very long period products can be maintained while ensuring continuing oversight
and influence from the research community. The GRP decided to continue working on the
formulation of these ideas to be forwarded to WOAP, GCOS and GEO.
The Global Precipitation Climatology Project is in its 21st year and has produced global
precipitation products covering the period from 1979 to April 2005. Processing beyond April
2005 will be delayed until the processing of infrared sounder data that provides estimates of
polar precipitation can resume, but a provisional product without the polar regions will be
released to keep current. Analysis of the 26-yr record shows a small 0.2%/decade trend in global
mean precipitation; but most of this signal arises in the tropics, which exhibits a 0.6% linear
increase per decade almost entirely over oceans, with smaller offsetting decreases over tropical
and northern midlatitude land areas. All GPCP centers are currently funded for the next few
years at least, but the status of the Validation center is uncertain. Some near-term improvements
in current version of the product were proposed and endorsed by the GRP including changing the
gauge product to the new GPCC 50-yr analysis (covering the period 1951-2000) and introducing
an adjustment as a function of altitude and climate zone. Studies are underway, including a
workshop on snow algorithms, to develop improvements for a third version of the products,
including a consistent analysis method for all products, a modern microwave analysis method
based on TRMM advances and adding an explicit snow discrimination algorithm. The plan is to
be ready for a complete re-processing by early 2007. Although no formal presentation was made,
it was reported that the Precipitation Product Assessment has progressed farther than the other
Assessment activities, having completed two workshops and having many chapters of the report
in draft form.
The Global Aerosol Climatology Project is in its 8th year and has produced a monthly
mean product over the global oceans providing aerosol optical thickness and Angstrom
coefficient (a measure of particle size) for the period from late 1981 through 2004. This record
shows the two major volcanic events (El Chichon, Mt. Pinatubo) and a consistently larger optical
thickness in the northern than the southern hemisphere. Theoretical analyses have established a
hierarchy of the accuracy and information content that can be obtained from various spaceborne
instruments, increasing from AVHRR (two-wavelength radiances) through MODIS and MISR
(multi-wavelength and multi-angle radiances) to POLDER and the planned APS (multi-wavelength, multi-angle, polarized radiances). The AVHRR-based GACP product has been
calibrated against a diverse collection of ship-based measurements. Comparison of the GACP
product with the MISR and two MODIS products shows significant disagreement in the mean
that are not yet understood. GACP funding is approved through 2006. If this project continues,
the newer instruments will be used to calibrate the AVHRR-based analysis more extensively (if
the current differences can be resolved) and used to extend the AVHRR-based analysis to land
areas. Although a working group was formed, the Aerosol Product Assessment activity did not
start, so a new group was constituted. Nevertheless comparisons of products have been made by
several individual researchers but much more needs to be done.
The International Satellite Cloud Climatology Project is in its 24th year and has produced
global cloud and radiation products covering the period from 1983 through 2004. Work is
currently underway to accommodate four new types of satellites, including NOAA polar orbiter
with a new AVHRR, the new EUMETSAT geostationary satellite, MSG-1 (METEOSAT-8), the
new Japanese geostationary satellite, MTSAT-1R, and notably, the Chinese geostationary
weather satellite (FY-2C). New products that are just being released (completed by the end of
this year) include (a) a method for analyzing the joint histograms of cloud top pressure and
optical thickness to identify distinct weather states (tropical results have been released), (b) a
composite survey of the cloud, radiation and precipitation associated with midlatitude cyclones
(including a cluster analysis and composites of cloud vertical structure from radiosonde humidity
profiles), and (c) a survey of twice-daily retrievals of cloud particle sizes for both liquid and ice
clouds. All centers are funded for the next few years. Work is underway on three improvements
of the products: refined cloud detection in the polar regions, reduction of the spurious angle
dependence in the retrievals (along with some other refinements of the angle treatment) and
substitution of more homogeneous ancillary data products to remove artifacts caused by changes
in these operational products. A complete re-processing of the products is planned for 2007.
Although no formal presentation was made, it was reported that the Cloud Product Assessment
has complete its first workshop and formulated plans for more detailed comparison
investigations. A supporting web site should be ready by the end of this year.
Globally complete water vapor datasets are available from the NOAA operational
analysis of HIRS/MSU (called TOVS, there are three versions) and from the several weather
reanalyses of conventional observations (i.e., radiosondes supplement now by infrared radiances
sensitive to upper tropospheric water vapor). These are supplemented by several SSM/I-based
analyses (ocean only) and a merged product (NVAP) produced as a pilot study under GRP.
There are also experimental products produced from GPS as well as various new infrared and
microwave instruments. Thus, the subject of the need for organizing a project to re-process
available measurements to produce a more accurate and uniform, global, long-term water vapor
dataset was re-visited. The GRP members had already been informed of the effort underway at
CM-SAF to produce a comprehensive global water vapor dataset focusing on the period covered
by newer instruments, eventually encompassing the more recent “microwave” period with
SSM/I augmented by AMSR. NOAA NCDC is also working with the main reanalysis centers to
improve and extend the long-term water vapor record obtained from infrared sounders, focusing
especially on the upper troposphere, but including a re-processing of the HIRS data. All these
efforts appeared to be sufficient and likely to produce better long-term, global water vapor
datasets in the near future, one based largely on infrared sounder measurements covering as
much as 30+ years and another including passive microwave measurements back to 1987. The
only area where work may be insufficient is in developing analysis methods for the new
microwave water vapor sounder instruments that work over land areas. The GRP decided for
now to keep under review the on-going efforts to improve the global water vapor datasets and to
consider what actions might foster progress in extending the use of the microwave water vapor
sounders to land areas. The new HIRS-based analysis being produced by NOAA NCDC may
serve the immediate needs of the ISCCP, GPCP and SRB projects for a more homogeneous
global record of atmospheric temperature and humidity over the period from 1979 to current.
In summary, all of the global projects seem to be on-track with all product deliveries up
to date and sufficient studies underway to develop improvements that could be implemented
during re-processing within the next two years. Funding beyond the next year or two is still
uncertain. The Precipitation and Radiation Product Assessments are also well underway to
support development of these improvements. The Cloud Product Assessment is lagging
somewhat and the Aerosol Assessment has to be re-started.
Wednesday morning, 5 October: The Working Group on Cloud and Aerosol Profiling
is comprised of operators of “high-end” cloud and aerosol profiling sites (i.e., collocated cloud
radar and lidar); the participating sites include the three CloudNet sites plus a Lindenberg site in
Europe and the five ARM sites. Discussions are underway to obtain participation from a
Japanese site. The US Department of Energy Atmospheric Radiation Measurement program
continues with solid funding and support. The most notable event was the first deployment of the
ARM Mobile Facility, which provides a full ARM site that can be moved. The next deployment
will be next year as part of the AMMA field experiment. The funding status for CloudNet is in
question, which is of concern for making progress on problems of aerosol-cloud interaction (see
below). The second meeting of the WG is scheduled for later in October 2005. The WG is
working to provide conversion software to allow for re-formatting of data products from all
these sites into each other’s formats so as to expand user access to the whole set of sites. Several
projects are also underway to cross-implement each other’s analysis methods on each site’s
products.
The International Radiation Commission’s 3D Working Group reported on their
activities of the past year, now in Phase 3. Web sites have now been established to provide the
test cases employed to study the 3D effects of solar radiation in clouds; a similar site is being
established to support studies of the interactions of radiation with 3D vegetation canopy structure
and of radiation scattered between the surface and cloudy atmosphere. A new round of
comparisons of 3D calculations is being planned. Another initiative is the release of a
“community” Monte Carlo code for calculating 3D radiative fluxes and radiances, the latter
being needed to advance remote sensing applications to account for 3D effects in the analysis of
measurements by the new generation of instruments. Also an online education resource on this
topic is being developed. A brief report on the status of the analysis of data from the SORCE
mission indicated that the available spread of absolute values of the solar constant is now 1361 –
1372 Wm!2 but that agreement among different instruments about variability, even at a very
detailed level, is excellent. Although a follow-on flight of the TMI on the NASA Glory mission
is planned, there are no plans to continue spectrally-resolved measurements, which is of concern.
The plan for a Continuous Intercomparison of Radiation Codes (CIRC) was presented:
this effort combines with and expands the idea of the Intercomparison of Radiation Codes in
Climate Models (ICRCCM) activity to provide the materials needed to test radiative flux codes,
including cases based on observations. In addition to a set of synthetic cases, where inputs are
specified and outputs are to be compared with state-of-the-art line-by-line codes, another set of
cases will be collected where the inputs are determined from measurements together with
measurements of the coincident top-of-atmosphere and surface radiative fluxes. These materials
are to be made available through an open web site that the ARM project has agreed to host. The
initial sets of synthetic and observation-based cases have been identified and are being prepared
for posting to the web site; the number and types of cases will be gradually increased over time.
The GRP recommended holding a workshop in 2006 at which the first comparisons using the
CIRC cases are presented as a way of initiating use of and comments on the web site and
beginning work to solicit cases from other research observation sites and programs. Of the three
organizational possibilities presented, the GRP recommended that CIRC be operated as a hybrid
of open cases, where users download the needed information and conduct their own code tests,
and closed cases, where users submit their results without knowing the answers. In all instances,
all results of comparisons should be made available with codes identified. The GRP also agreed
that, after the first phase of CIRC is completed, a relationship with IPCC should be explored so
that the radiation codes in the climate GCMs used for IPCC scenarios are evaluated against the
CIRC cases and standards.
In a discussion of future directions in radiation, it was concluded that the emphasis of
research must now focus on the quantitative use of new kinds of remote sensing instruments that
provide multi-wavelength, polarized and “active” radiation measurements and that the near-term
issues are to account for the vertical structure of the atmosphere and 3D effects on these new
measurements. The topic of better calibration for the satellite constellation, including the newer
instruments, arose again, emphasizing the urgent need for this improvement of the satellite
observing system. Moreover, this discussion highlighted the need for a complementary surface
network for calibration as well as network-wide calibration standards for the surface observing
system.
The SeaFlux activity has received new funding and some new groups have expressed
interest in participating, so this activity has been reactivated. A workshop is planned for early
March 2006 to resume the planned comparison of all global products in the common year 1999,
with an emphasis on comparing those products using “older” instruments (visible, infrared,
passive microwave) with products using “newer” instruments (including scatterometers and
altimeters). Once the product comparisons are completed, the next phase will be to implement
improvements already identified from the previous phase of the project and to work on
remaining open questions concerning high-wind regimes and fluxes in coastal and polar waters.
It may be that this project will reach a maturity in the next few years that would allow the data
processing to become operational.
An invited presentation by Herve Douville from Meteo-France provided an overview of
the key factors governing the land surface hydrological processes and how they are represented
in current-day models. These models now include a complex variety of processes that depend on
the terrain (e.g., river routing), the nature of the soil and vegetation, as well as atmospheric
processes and all needing verification. However, the strength of the coupling between land and
atmospheric water processes is highly model dependent as well as varying strongly regionally so
the accuracy of regional climate change predictions with these models is in doubt. Satellite and
systematic in situ observations are needed to specify physical characteristics represented in
models and validate their processes, to initialize the land surface state for seasonal predictions or
for assimilation in forecast systems, and to monitor long-term land surface variations. Some key
parameters that might be determined from satellites now are snow-free and snow-covered
surface albedos, some measure of soil wetness (probably best from analysis of combined
infrared, active and passive microwave measurements) and surface skin temperature (diurnally
resolved). Systematic global, long-term surveys of these parameters have not yet been
performed.
An invited presentation by Philippe Ciais from the Laboratoire des Sciences du Climat et
de l’Environment provided an overview of the key factors governing land surface carbon cycle
processes. Important monitoring tasks for satellites include determinations of deforestation, fire
occurrence frequency, space-time-resolved atmospheric composition variations, some measure
of surface vegetation, surface temperatures, as well as providing “forcing” by solar radiation and
precipitation. A crucial point was made that, since the carbon and water cycles on land are
coupled strongly by the biosphere, the joint study of both of these would be better than the
separate study. Although there have been many regional studies, systematic global, long-term
surveys of these parameters have not yet been performed. An example was given where the
climate impact of a forest fire changed sign over time because of the complex feedbacks between
the land surface and atmosphere.
Wednesday afternoon, 5 October: An invited presentation by John Roads, chairman of
the GEWEX Hydrometeorology Panel, reviewed the activities and studies underway to
understand the land-atmosphere interaction based on a set of large field experiments. The field
phase of these experiments is now finished (with the exception of newer projects such as
AMMA). Three topics were of special interest in the discussion following the presentation:
datasets available from the continental scale experiments for evaluation of the global data
products, regional energy and water budget studies being conducted as part of these experiments
and studies underway to evaluate the utility of such datasets for regional water applications. A
notable problem with completing these regional water budgets is that surveys of surface
evaporation were not performed.
An invited presentation by Toshio Koike (Project Manager) provided an overview of the
Coordinated Enhanced Observation Project (CEOP) that conducted a two-year collection of data
to document land-atmosphere interactions at 35 sites, many within the same areas as the GHP
experiments. The data collection phase was completed last year but only about 25% of the data
have archived to date. Now a research and analysis phase is beginning. A similar focus of the
following discussion concerned availability and access to data products from CEOP. CEOP has
developed a much better and more complete data archival and dissemination system, so as these
analysis products become available, they should prove useful for evaluating the global products
produced by the GRP projects.
After all these presentations concerning research needs and activities focused on land-atmosphere interactions, the GRP discussed its proposed LandFlux initiative and the role that a
reconstituted International Satellite Land Surface Climatology Project could play. The GEWEX
Executive Committee had decided that the next phase of ISLSCP should be conducted in closer
cooperation with the other global satellite projects overseen by GRP. Already being discussed is
a joint workshop with the Global Soil Wetness Project to employ the global satellite data
products to evaluate the GSWP model inputs and outputs. At the last ISLSCP workshop, it had
already been suggested that this workshop could be used to define the remote sensing tasks
needed to complete the characterization of the global energy and water exchanges over land. A
key point noted in the discussion is that a comprehensive radiative transfer model for land
surfaces, especially with vegetation, is lacking which has significantly limited progress. This
lack will necessitate consideration of combined analyses to infer the needed information
indirectly. It was decided to recommend that the next phase ISLSCP activities should take as its
primary goal the development of global data products for the turbulent fluxes of energy and
water over land. As practical steps towards this goal, ISLSCP should follow a course parallel to
SeaFlux: (a) “clean up” where needed the radiances that are to be used for remote sensing of the
main relevant land parameters (albedo, skin temperature, fire occurrence, vegetation index, soil
wetness index), (b) produce an extensive compilation of in situ land surface flux measurements,
(c) evaluate available satellite-based products and (d) develop methodologies for inferring these
fluxes. Once evaluations of products are underway and possible methodologies have been
identified, funding can be sought for production of global data products.
A discussion of future directions for precipitation activities began by noting that an
initiative for comparing newer, high space-time resolution precipitation products had been
proposed by P. Arkin and that an international workshop was planned for the following week to
evaluate possible snow algorithms. The GEWEX Executive meeting suggested that the former
activity might form the core of a GEWEX Precipitation Cross-cut; the GRP endorsed this idea
and recommended that such a comparison study give special attention to evaluating how well we
can determine precipitation in mountainous terrains. It was noted that Japan also has begun an
activity (called GSMAP) to produce global precipitation at higher resolution. Plans for
implementing a snow algorithm in the next version of GPCP will be formulated based on the
outcome of the workshop. The rest of the discussion focused on organizing a new working group
on Precipitation Radar Networks to foster the dissemination and use of this type of data, similar
in concept to WGCAP. V. Levizzani has volunteered to chair this working group; Machado,
Bates and Rossow agreed to draft some terms of reference. The first steps suggested for this
group are to find out what networks exist and who would be interested to joining the working
group (hold a first workshop), to find out what the current status of archival of this type of data
is and to identify possible common products that might be produced for a common time period.
Two brief reports were presented on surface network activities with regards to aerosols.
Z. Li presented an update on a China-USA cooperative project to build an aerosol and radiation
network in China. The network will have multiple sites providing coverage of China
representing the major aerosol source regions and background conditions. A crucial feature of
the design of this network, which the GRP strongly endorsed, is that the set of measurements
includes not only aerosol determinations by multi-wavelength sun photometers but also standard
meteorology and surface radiative fluxes meeting BSRN standards. E. Dutton presented an
overview of current aerosol networks: how many sites and the type of measurements being
made. By far the largest network is AERONET with about 150 sites (but only about a third of
these sites deliver the majority of the possible observations); both the GAW network and SkyNet
each have about 10 sites. Since about 20 of the BSRN sites actually make aerosol sun
photometer measurements, BSRN is actually the second largest aerosol network; however, the
resources are not available currently to archive these data. A WMO/GAW workshop was held in
March 2004 to evaluate what is being done: they identified 10 independent networks with about
90 sites having data records of 4 years or longer but with significant coverage gaps over Africa,
India, Latin America and the polar regions. Very little ocean aerosol data exist (GACP has
compiled a significant collection). This workshop formulated a number of good recommendation
for establishing better monitoring of aerosols. The following discussion led to two conclusions
and a recommended course of action. The leading climate questions involving aerosols concern
the magnitude of their direct radiative effect and the importance of the interactions of aerosols
and clouds in determining climate sensitivity. Other important scientific issues relate to the role
that aerosols and aerosol-cloud interactions play in determining the composition of the
atmosphere. The first conclusion is that, from a climate perspective, aerosol measurements made
without corresponding meteorology and surface radiative fluxes are not useful. The second
conclusion is that no existing or planned measurement system directly observes the interaction
of aerosols and clouds. Thus, the GRP recommends funding support to pursue the following key
actions: (a) the differences among advanced satellite aerosol products must be reconciled (this
effort will be aided by use of surface measurements of aerosols at sites that also measure surface
radiative fluxes and meteorological conditions) to allow extension of the longer-term AVHRR-based record to land areas and to provide overall calibration of this record, (b) a surface-based
aerosol network that provides better coverage needs to be built and the most practical way
forward appears to be to augment the BSRN network, which is already the GCOS radiation
element, to include aerosol measurements, to implement a “broadband” cloud analysis and to
increase site coverage in poorly sampled areas (the China-NASA network is a key addition), and
(c) ARM-like sites should begin investigating how they might be instrumented to attack the
aerosol-cloud interaction problem directly. This course of action should not preclude efforts to
develop a broader aerosol monitoring network, including compositional measurements, but the
greatest need is to develop some ocean-based measurement capability to BSRN standards. The
third item is predicated on the fact that ARM-like sites may have nearly the set of instruments
needed and collect long-term datasets that allow for studies under many different meteorological
conditions; however, a focused analysis of the combined data products from these sites is needed
to see if this approach will work.
Thursday morning, 6 October: A review of presentations and discussions at the
meeting led to the conclusion that the global data projects are all on-track and that three of the
four Product Assessment activities are well underway. It was further concluded that: (1) GRP
needs to keep activities at NOAA and EUMETSAT under review but that there does not appear
to be a need for a special water vapor project at this time, (2) GACP can be re-invigorated to
foster reconciliation of the available satellite aerosol products to allow for calibration and
extension of the long-term record to land areas, and (3) the Working Groups and Study Projects
are also progressing well but that action is now needed to organize a Working Group on
Precipitation Radar Networks. Review of the GRP Plan (published on the GRP web site) did not
lead to any recommended changes: the focus is still on completing the measurements needed to
characterize and diagnose variations of the global energy and water cycle.
The WCRP Observation and Assimilation Panel has endorsed the concept of a
coordinated re-processing of the global, long-term data products as has been discussed by GRP
for the past couple of years. Both GCOS and GEO have also begun discussing this idea. The
GRP has therefore asked its Working Group on Data Management and Analysis to formulate
specific plans for a coordinated re-processing of the GRP data products to be reported at the next
GRP meeting. This plan should include specific information concerning the product
characteristics (record length, map grid and time intervals), needed improvements in retrievals,
needed product cross-connections for consistency, and desired enhancements of quantities
included in the products.
Before adjourning, the chairman extended thanks to retiring members, Arnold Gruber,
James Haywood and Andreas Macke and asked two members, Tadahiro Hayasaka and Toshio
Iguichi, to extend their membership for two more years. The next meeting of the GRP will be
part of a planned pan-GEWEX meeting of all panels, possibly in Frascati, Italy, in October 2006.
Recommendations
(1) The GEWEX SSG should write a letter to ESA expressing concern about support for EGPM.
(2) NOAA and EUMETSAT should share their radiance calibration results with ISCCP
(EUMETSAT has forwarded its results).
(3) CERES should consider producing a homogenized flux product that combines TERRA and
AQUA results using a common Angle Dependence Model.
(4) BSRN should find a way to produce summary products (e.g., daily and monthly means) that
are freely available. Staff at the BSRN archives must more clearly separate their own research
products from those of the BSRN, which should be available with no restrictions on use.
(5) China and the US should implement the planned Aerosol Network as this plan outlines a
more useful aerosol-radiation-cloud measurement set that is preferred by the GRP.
(6) NOAA should develop its BSRN sites into full Surface Energy Budget sites. This evolution
should also be considered by the CEOP sites and should be incorporated into the GCOS plan.
GCOS should initiate international discussions to foster this evolution for the whole BSRN
network.
(7) GPCP, in preparing to produce its next version products, should “rationalize” the analysis
sequence for better consistency and more uniformity among the components. In order to exploit
lessons learned from TRMM and to evaluate the inclusion of a snow algorithm, as well as
possible improvements to be made over mountainous terrain, a new algorithm evaluation should
be undertaken before the next version products are produced.
(8) GACP needs to formulate a plan to obtain some estimate of aerosol optical thicknesses over
land areas.
(9) All Projects appear to be functioning satisfactorily and should continue with planned
activities.
(10) The Precipitation and Radiation Assessments appear to be progressing satisfactorily and
should continued as currently planned, but the Clouds Assessment needs to move forward more
aggressively. The GRP will re-start the Aerosol Assessment (Z. Li and X. Zhao have agreed to
co-chair this activity).
(11) GRP recommends that the NASA instrument teams producing aerosol products join in the
Aerosol Assessment to provide the needed “calibration” of the long-term GACP record.
(12) WGCAP is urged to release the (experimental) common products as soon as possible so that
some preparation for activities during CloudSat/Calipso operations can be made.
(13) The CIRC plans are solid and so they should be implemented aggressively using the hybrid
scheme with open (not anonymous) results. Once the first cases are posted on the web site, CIRC
needs to consider how to develop cases from other sources besides ARM and to add more
spectral measurements, especially space-borne, to the data provided. Once the first cases are
posted, CIRC should organize a comparison workshop to foster use of the site and to collect
suggestions for its improvement.
(14) GEO/GCOS should strongly urge the participating satellite agencies to develop a calibration
satellite for the whole satellite constellation (both broad and narrowband radiances) and should
urge participating operators of surface networks to develop network-wide calibration procedures.
(15) The plans of the revitalized SeaFlux project are good and should be implemented.
(16) The new goal of ISLSCP should be to determine the global distribution of the land surface
turbulent fluxes of heat and water and their space-time variations. To that end, the next tasks
should include at least: (a) compilation of in situ validation datasets specifically for turbulent
fluxes (CEOP may contribute to this), (b) evaluating the state of available satellite radiances that
can be used to measure relevant land surface properties, and (c) organizing workshops to
evaluate remote sensing products, focusing on albedo and skin temperature but also assessing the
state-of-the-art for near surface meteorology, soil wetness indicators and vegetation properties.
In the near-term, ISLSCP should participate in a joint workshop to evaluate the models and
products from the GSWP-2 effort. This evaluation effort should lead to identification of a
methodology for estimating the land surface turbulent fluxes.
(17) The GRP endorses plans to organize a comparison of newer, higher resolution algorithms
for estimating precipitation from satellites and recommends that this activity focus especially on
precipitation in mountainous terrains.
(18) The GRP/GPCP request that the participants in the recently completed snow algorithm
workshop provide advice on whether a practical method exists or can be developed that can be
incorporated into the GPCP analysis.
(19) An plan of action to advance aerosol studies for climate was developed from the GRP
discussions involving four activities: (a) the substantial disagreement between NASA aerosol
products from different instruments flying on the same satellite should be resolved to understand
current limitations of aerosol remote sensing, (b) the results of this investigation should be used
to “calibrate” the longer AVHRR-based records produced by NASA and NOAA to arrive at the
best climatology, (c) the BSRN network should move ahead with plans to add capabilities for
aerosol and cloud measurements to radiative flux measurements, and (4) WGCAP needs to
foster beginning work on the development of a measurement suite at ARM-like sites that may be
able to examine the evolution of air parcels from clear, aerosol laden, conditions to cloudy
conditions over long enough time periods to provide a more generalized understanding of how
aerosol properties affect the evolution of clouds and precipitation. This plan will be forwarded to
the cognizant funding agencies to recommend their support.
Actions
(1) All GRP members should provide to the chairman comments on the GCOS IP by the end of
October (DONE)..
(2) All GRP members should suggest to the chairman milestones for GRP activities that
contribute to the GEWEX plan by the end of October (DONE).
(3) J. Bates and J. Schulz will keep activities at NOAA and EUMETSAT CM-SAF with regard
to producing water vapor products under review and will report at the next GRP meeting as to
whether these activities will meet GEWEX needs for improved water vapor datasets (Bates
already forwarded the recent Upper Air Workshop Report).
(4) SRB should report at the next GRP meeting on the quality of the GEOS-5 temperature and
humidity profiles being used with respect to other sources of this information so as to determine
the best product to be used for the next version of the SRB products.
(5) The co-chairs of the Radiation Assessment (Stackhouse, Wielicki) should send out as soon as
possible to potential participants in the next workshop the list of proposed actions to be
completed by the time of that workshop. If responses are inadequate or suggest that many of
these activities will not be complete, then the workshop planned for February 2006 should be
postponed by 3-6 months.
(6) GRP members (with J. Bates and W. Rossow leading) will formulate some thoughts about
“best practices” for producing climate data records and about how to convert research data
analysis activities to operational analysis activities. These thoughts will be forwarded to WOAP
for consideration with the recommendation that WCRP suggest crucial attributes of climate data
records and their production to CEOS, GCOS and GEO.
(7) W.Rossow, J. Bates, N. Loeb, T. Ackerman and B. Wielicki will develop draft language
supporting the calibration satellite and network calibration concepts to be forwarded through
WOAP to CEOS by the end of October (DONE).
(8) To launch an international working group on precipitation radar networks (WGPRN), W.
Rossow and J. Bates will draft goals to be conveyed to the working group chairman (V.
Levizzani). V. Levizzani, T. Iguchi, L. Machado and J. Bates will provide contacts to
representatives of radar networks in Europe, Japan, Brazil and US-Canada, respectively, to build
up the initial working group membership. Initial tasks of the working group should include a
survey of current operational observing strategies and status of data archival. Further information
will be sought from the WCRP JPS contacts at WMO and from weather forecasting groups
through WGNE.
Issues
(1) NOAA and EUMETSAT need to decide who will deliver METOP imager data to ISCCP and
GPCP.
(2) More attention is needed to develop better capability to obtain water vapor profiles from the
new microwave sounder instruments over land areas.
(3) The future of the BSRN archives needs to be resolved so that it can not only continue but
expand its functions to include aerosol and cloud products. There are several institutional options
being discussed. If GEWEX supports this more aggressive attack on aerosol problems then the
SSG should seek this expansion of BSRN in support of GCOS.
(4) Following the example of BSRN, it may make sense for GPCC to become the surface-based
reference component for precipitation within GCOS.
(5) The status of the GPCP validation center is not known and needs to be clarified.
(6) To develop a surface network of total Energy fluxes, the GEWEX SSG should strongly
support the idea by urging CEOP to carry out this development for its sites and recommending
that GCOS adopt this pathway.
(7) The status of CloudNet is not known and needs to be clarified.
Attendance List
Members
> William B. Rossow, chair (NASA Goddard Institute for Space Studies)
> John J. Bates (NOAA NESDIS, National Climatic Data Center)
> Abderrahim Bentamy (Institut Francais pour la Researche et l'Exploitation de la MER,
IFREMER)
> Tadahiro Hayasaka (Research Institute for Humanity & Nature)
> Toshio Iguchi (National Institute of Information and Communications Technology, NICT)
> Zhanqing Li (University of Maryland, Earth System Science Interdisciplinary Center)
> Norman G. Loeb (NASA Langley Research Center)
> Luiz A.T. Machado (Instituto Nacional de Pesquisas Espaciais, Centro de Previsao de Tempo,
e Estudos Climaticos)
> Catherine Prigent (Observatoire de Paris, Department de Radioastronomie Millimetrique)
WG Chairs and Study Leaders
> Tom Ackerman (Pacific Northwest National Laboratory, PNNL)
> Robert F. Adler (NASA Goddard Space Flight Center)
> Robert F. Cahalan (NASA Goddard Space Flight Center)
> Carol Anne Clayson (Florida State University)
> Ellsworth G. Dutton (NOAA Climate Monitoring and Diagnostics Laboratory)
> Michael I. Mishchenko (NASA Goddard Institute for Space Studies)
> Paul W. Stackhouse (NASA Langley Research Center)
GEWEX/WCRP
> Toshio Koike (CEOP)
> Richard Lawford (IGPO)
> John Roads (GHP, Scripps)
> Gilles Sommeria (WCRP)
Space Agency and Mission Representatives
> Yves Govaerts (EUMETSAT)
> Paul Ingmann (ESA)
> Jacqui Russell (GERB, Imperial College)
> Joerg Schulz (EUMETSAT CM-SAF, Deutche Wetterdienst)
Invited Experts
> Filipe Aires (Laboratoire Meteorologie Dynamique)
> Sandrine Bony (Laboratoire Meteorologie Dynamique)
> Philippe Ciais (Laboratoire des Sciences du Climat et de l’Environment)
> Herve Douville (Meteo-France)
> Martial Haffelin (Laboratoire Meteorologie Dynamique)
> Ehrhard Raschke (University of Hamburg)
> Genevieve Seze (Laboratoire Meteorologie Dynamique)
> Claudia Stubenrauch (Laboratoire Meteorologie Dynamique)
2005 Meeting of the GEWEX Radiation Panel
Dates: 3-6 October 2005, Paris, France
Location: Observatoire de Paris, Paris, France
Agenda – Final for 2005
03 October 2005 Salle du Conseil
0830-0930: Executive Session: Discussion Topics and Meeting Goals
0930-1000: Welcome (Director of Paris Observatory), Local Arrangements (Prigent)
1000-1030: WCRP Report (Sommeria)
1030-1100: Break [Peak of Partial Solar Eclipse]
1100-1130: GEWEX Report (Lawford)
1130-1300: Satellite Agency Reports
(ESA - Ingmann, INPE - Machado, JAXA - Iguchi)
1300-1400: Lunch
1400-1500: Satellite Agency Reports (NOAA - Bates, EUMETSAT - Govaerts)
1500-1530: Special Report (EUMETSAT CM-SAF - Schulz)
1530-1600: Break
1600-1630: Discussion of Calibration of Satellite Constellation
1630-1700: Report on GERB (Russell)
1700-1730: Global Data Project Report: CERES (Loeb)
1730: Adjourn
1800: Reception
04 October 2005 Salle de l’Atelier '' Note Room Change
0830-0900: New Member Science Presentation (Loeb)
0900-0945: Global Data Project Report: SRB (Stackhouse)
0945-1030: Global Data Project Report: BSRN (Dutton)
1030-1045: Discussion of BSRN Archives
1045-1115: Break
1115-1200: Data Product Assessment Report: Radiation (Stackhouse/Raschke)
1200-1230: Hosted Science Presentation (Bony)
1230-1300: New Member Science Presentation (Machado)
1300-1400: Lunch
1400-1445: Best Practices to Produce Climate Data Records (Bates)
1445-1530: Global Data Project Report: GPCP (Adler)
1530-1600: Break
1600-1630: Discussion about Activating GVAP
1630-1700: Global Data Project Report: GACP (Mishchenko)
1700-1730: Global Data Project Report: ISCCP (Rossow)
1730-1800: Discussion about Project Status and Product Assessments
1800: Adjourn
Agenda – Final for 2005
05 October 2005 Salle du Conseil
0830-0900: WGCAP Report (Ackerman)
0900-0930: Study Project Report: 3DWG (Cahalan)
0930-1000: Study Project Report: CIRC (Loeb)
1000-1030: Discussion about Radiation Activities
1030-1100: Break
1100-1145: SeaFlux Report (Clayson)
1145-1300: Hosted Science Presentations (Ciais, Douville)
1300-1400: Lunch
1400-1430: GHP-GWEBS (Roads)
1430-1500: CEOP Phase II (Koike)
1500-1530: Discussion about LandFlux Initiative and ISLSCP
1530-1600: Break
1600-1630: Discussion about Precipitation Initiatives
1630-1700: Status of BSRN/AERONET sites in China (Li)
1700-1730: Report on BSRN Aerosol Initiative and Other Aerosol Networks (Dutton)
1730-1815: Discussion about Aerosol Activities
1815: Adjourn
1945: Group Dinner on Seine River
06 October 2005 Salle du Conseil
0830-0930: Review of GRP Activities
(Radiation, Precipitation, Aerosols, Surface Fluxes)
0930-1030: Discussion: Product Assessments and Joint Data Re-Processing Activity
(Recommendations for WGDMA)
1030-1100: Break
1100-1300: Executive Session: Assignments and Wrap-up
1300: Adjourn
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