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).