Plan for the Re-organization and Re-direction of GEWEX
Radiation Panel
by William B. Rossow
I. Background Issues
At beginning of WCRP, there were very few global datasets with a
resolution sufficient to resolve the dynamics of processes in a
climate context (= satellite-based, primarily) and almost all the
relevant satellites were operated by NOAA, NASA and DOD in
the US. None of these operators had a "climate" mandate. Usually,
all we had were published papers with highly summarized forms of
information gleaned from larger datasets. Note that, even today,
the only quantitative, global, long-term datasets from weather
satellites are SST, TOVS, ISCCP and GACP, all of which date
from the early 80's except for the aerosol products. The first
systematic, long-term datasets from NASA were from NIMBUS-7
(ERB, NCLE, TOMS, SAGE), released in mid-80's, followed later
by ERBE and now CERES. Also UARS produced a decade of
stratospheric observations. We are now entering a period where
there is a very large number of satellites producing more data than
can be used; these satellites are operated by NOAA, NASA, DOD,
ESA, EUMETSAT, NASDA, JMA, CMA, IMA (and more are
coming).
Traditionally, there has been lots of funding support for regional
experiments and process studies but not for global data analyses.
Global studies are usually equated with global modeling, but the
NWP focus on forecast improvement has, oddly enough, not led to
improved global datasets nor to their systematic analysis. Climate
modeling studies call for global datasets all the time, but have not
produced support for global data analyses. Both modeling groups
are more interested in improving their models, often equated with
improving their computer facility. Hence, we now have a surfeit of
global observations, most of it in the form of raw radiances (often
uncalibrated), some of it in the form of measurements of basic
state variables with a fair amount of duplication, but very few
global diagnostic products. A diagnostic product tells not just the
values and variations of some variables but the rates of change and
exchanges of energy/mass — i.e., what is going on.
Given the paucity of global datasets, WCRP started with a couple
of projects (ISCCP, GPCP, WOCE) to produce key missing "state
variable" datasets, but WCRP evolved only one diagnostic project
(SRB). GEWEX has added only one "state variable" project
(GACP) and has been discussing another (GVAP), but has added
no global diagnostic projects until advent of SeaFlux (ISLSCP has
started in similar direction after a long period of focusing on field
studies). Note also that the operational agencies did NOT pick up
routine processing tasks such as ISCCP as expected!
GEWEX cannot probably continue to act as the sole creator of
global datasets, especially since these projects appear to compete
with the large number of satellite missions with large processing
teams producing similar datasets. NASA has been the sole agency
supporter of intensive data processing (with smaller contributions
from NOAA, ESA, EUMETSAT, JMA), but it is now losing
interest because these projects appear to be duplicative of their
own projects (they are not!). Nevertheless, although all this new
project-specific activity will produce large volumes of data, it is
not likely to provide much useful assessment of the relative quality
of these datasets (i.e., data product comparisons will not likely be
done by the individual teams) and some needed measurements
may still be missing. So, GEWEX will need to continue its review
of the whole situation. There is still little real support for the
sustained effort required to produce long-term, global datasets
(current NASA thinking seems to deny the value of such an effort,
but NOAA is trying to get funding for some such activity and
EUMETSAT now has a climate mandate). Thus, GEWEX needs to
shift to more of an integration role: although lots of "state
variable" products will become available, there is still very little
attention paid to cross-satellite, cross-instrument, integration and
analysis of these datasets into comprehensive, long-term,
diagnostic data products that can be used to figure out what is
going on at climate scales. A notable exception is CERES.
One more important historical note is that, in the original
conception, all of these global projects were supposed to be
supported by regional and process experiments, mostly as national
or regional initiatives, to provide evaluations and improvements.
This relationship has not worked nearly as well as it could/should.
The participants in these experiments tend to focus on their own
datasets and analyses of them and to forget the "chore" of
evaluating the global satellite products, usually assuming that this
is really the responsibility of the producers of these products
anyway. But the global product producers have not been given
adequate resources for such work and have NOT been able to get
well-prepared/documented, comprehensive data products from the
experiments in order to perform these evaluations or to develop
improvements. This situation applies to all the CSEs, too.
II. Focus and role of new panel
Radiative transfer is a key climate process but this research area is
very mature relative to some others (e.g., precipitation, hydrology,
biospheric processes). Current research activities are more about
the use of radiative transfer as a tool (i.e., SRB, SeaFlux) than
about its advancement. Specifically, "large-scale" flux calculations
are much more accurate than input variables; the final stages of
improving these calculations for inhomogeneous media (broken
clouds) are underway. However, there are two frontiers: (1)
coupling of radiation and turbulent/convective dynamics at scales
where atmospheric motions and radiation are 3-D and (2)
advanced radiative transfer codes that can calculate in
inhomogeneous scattering-absorbing media the high-resolution
spectra, high-precision polarization, and coherent radiances needed
to analyze the advanced remote sensing measurements now
becoming available. The latter also requires development of more
capable analysis methods that can exploit more of the physics and
allow multi-wavelength, multi-instrument analyses.
The research community is not using the global datasets to
diagnose global exchanges and/or budgets, so more needs to be
done to stimulate this activity: (1) produce comprehensive data
product packages for such research (inspired by ISLSCP and
SeaFlux) and (2) stimulate development of advanced non-linear
analysis methods that can combine large numbers of variables with
relatively high time-space resolutions but with global, multi-year
coverage.
GEWEX (and WCRP) needs to repair its relationships with the
space and weather agencies to get more substantial participation by
those other than NASA and to continue NASA's traditionally
strong participation. This may require some "re-packaging" of the
needed activities to define, more explicitly, mutually beneficial
activities that are global in extent (hence, natural for international
collaborations).
GEWEX activities need to define better the things that can actually
be done and focus on deliverables.
GRP specifically needs to change its approach by forming more
aggressively active working groups, especially ones that combine
observationalists and modelers (inspired by the successes of
GCSS and GLASS).
III. Six Tasks and Four Collaborations.
A. Radiation split into One Task and Two Collaborations.
1. WG1: Advances in Remote Sensing and Analysis (a standing
working group) — focus on development and testing of advanced
radiative transfer codes for spectra, polarization, active sensors
(coherent and incoherent) and on the development of advanced
multi-variable, non-linear analysis techniques. Deliverables: Web
site for codes and methods, sponsor series of workshops and
journal special issues.
2. Collaboration 1 (with GMPP, WGNE/AMIP, ARM): evaluation
of GCM flux codes (used to be ICRCCM) = ICRCCM-SW
(Barker) + ICRCCM-LW (Ellingson) –> ARM data. Deliverables:
Comparison kit CDs (cases and reference model results) in 3 years.
3. Collaboration 2 (between ICRCCM-3 and GCSS, GABLS,
GLAS): Phase 1 (currently underway) — evaluation of 3-D
radiative transfer codes; Phase 2 — evaluation of coupling of
efficiency of radiation at 3-D scales with convective clouds,
boundary layer turbulence and land surface. Deliverables: answers
in 3-4 years.
B. Global Data Projects — Four Tasks.
1. WG2: Cloud and Aerosol Interactions (a standing working
group, merger of ISCCP, GACP, SRB, GVAP plus reanalyses) —
diagnosis of cloud-aerosol interactions (dynamics and cloud
physics). Deliverables: merged data (model?) product (CDs) with
cloud and aerosol properties plus radiative fluxes and meteorology
(humidity, winds) in 5-6 years, sponsor 1-2 workshops, Web site.
2. WG3: Clouds and Precipitation (a standing working group,
merger of ISCCP, GPCP, GVAP, plus reanalyseis) — diagnosis of
precipitation formation in clouds, feedback of latent heating on
atmospheric circulation, and feedbacks between precipitation
effects and cloud radiative properties (dynamics and cloud
physics). Deliverables: merged data with cloud properties,
meteorology (temperature, humidity, winds) and precipitation
sorted by cloud type (CDs) in 5-6 years, sponsor 1-2 workshops,
Web site.
3. WG4: SeaFlux (a standing working group, subsumes SRB) —
diagnosis of global ocean (including sea ice) surface energy,
freshwater and momentum fluxes. Deliverables: global ocean
surface properties, PBL properties, and surface fluxes product
(CDs) in 5-6 years, sponsor 1-3 workshops, Web site.
4. WG5: LandFlux (a standing working group, maybe
collaboration with ISLSCP and/or GLASS-GWWP, subsumes
SRB) — diagnosis of global land (including permafrost) surface
energy and water fluxes. Include carbon and other biochemical
fluxes ??? Deliverables: global land surface properties, PBL
properties, and surface fluxes product (CDs) in 5-10 years (longer
if carbon and other biochemical fluxes), sponsor 1-3 workshops,
Web site.
ALSO: Clouds and Radiation: The GRP will continue to review
this area, but the real action is in CERES and other specific
projects (i.e., GERB). Deliverables: sponsor international
workshop, review paper.
C. Global Diagnostics — Whole panel will work together on One
Task and Two Collaborations.
1. Natural climate variability and feedbacks — development of
advanced, multi-parameter, non-linear, high resolution analysis
methods. Deliverables: sponsor workshop series, Web site for
methods.
2. Collaboration 3 (with GMPP, WGNE, WGCM) — diagnosis of
atmospheric transports of energy and water, relation to surface and
top-of-atmosphere fluxes, and role in creating natural climate
variability. Deliverables from GRP: atmospheric transports
inferred from boundary surface fluxes (CD).
3. Collaboration 4 (with CLIVAR-WGCM) — diagnosis of
oceanic transports of energy and freshwater, relation to surface
fluxes and role in creating natural climate variability. Deliverables
from GRP: oceanic transports inferred from boundary surface
fluxes (CD).
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