GRP Mid-Year (2003) Report to GEWEX SSG

Global Satellite Projects

Global Datasets Now Available and the periods they cover are: ISCCP clouds and radiative fluxes (1983-2001), SRB radiative fluxes (1983-1995), GPCP precipitation (1979-2001), GACP ocean aerosols (1983-2001), NVAP water vapor (1987-1998) and the ISCCP-version of NOAA TOVS water vapor (1981-2001). These global datasets are supported by the BSRN radiative fluxes collection (1994-2001) and the GPCC gauge precipitation collection (1979-2001). A long-term, nearly-global ERB dataset (1978-2002) has been constructed and a new version of a long-term, global ocean surface latent and sensible heat flux dataset (1987-2000) has been released based on SeaFlux activities (another is to be released later this year).

GVAP: GVAP has already completed a pilot phase, producing the NVAP dataset, and has successfully encouraged and participated in field campaigns to evaluate water vapor measurement systems. Considering the number of global water vapor datasets currently available (counting NVAP and the re-analyses, at least 6), the GRP WGDMA recommends that the next phase of GVAP be a rigorous assessment of the accuracy of the long-term water vapor datasets in partnership with the International TOVS Working Group. This assessment could include comparisons with results from newer satellite instruments and contribute to the next IPCC assessment report.

ISLSCP: Over the past 5+ years, this project has focused on producing collections of global data to study land-atmosphere interactions, but there is still a significant need to improve the rigor and expand the range of land parameters derived from satellite observations to complete the diagnosis of the global energy and water cycle over land areas. These goals might be better served if ISLSCP (as its name implies) were included with other global satellite projects under GRP to provide better liaison with GSWP. My information is that the funding for ISLSCP (essentially reduced to the activities of a group at NASA GSFC) was extended only to complete the Initiative-2 data compilation but not for an Initiative-3.

WGSM: The WCRP Working Group on Satellite Matters, which recently assessed requirements for space missions (with major input from GEWEX), has now been tasked by the JSC to produce a comprehensive re-analysis plan for global, long-term (mostly satellite-based) data products.

Evaluation Projects

BSRN: More than 1800 data-months are now available from the central archives, representing an average of 4 years of data from 35 functioning sites in 19 countries. The GRP/WGDMA recommends that ETH now explore the feasibility of also acting as the archives for surface-based determinations of evaporation (and sensible heat flux) from and the latent heat of freeze-thaw on the land, possibly collected from FLUXNET and CLIC sources. This recommendation would effectively expand the BSRN archives activity back to the full GEBA concept (all surface fluxes) but with the crucial addition of site atmospheric properties including aerosol optical thickness. Discussions with GCOS AOPC have led to a plan for BSRN/GRP to lead the formulation of the plan for BSRN to evolve into the radiation monitoring component of GCOS.

Study Projects

SeaFlux: A workshop was held on 12-13 February 2003 at Long Beach, California, to evaluate progress on the several comparison activities. Work on improving the bulk formula used to calculate fluxes from surface and atmospheric properties appears to be winding down; so the focus of effort now is on completing the comparisons of the various global products. Some work is still needed to obtain better skin SST (in collaboration with GODAE-SST) and air temperature/humidity.

LandFlux: Discussions with participants in GSWP are being used to formulate a plan to produce global, long-term versions of key land surface datasets (latent and sensible heat fluxes) to close the global energy and water budget. Currently, GSWP gets some (but not all) GRP products through ISLSCP, but this indirect interaction does not take full advantage of the GRP expertise. Moreover, there are still a few land surface parameters (albedo, skin temperature) that lack a good global dataset.

Feedback WS: A plan is being formulated to provide (on a Web site) a common, comprehensive set of global data that can be used by various researchers to analyze climate feedbacks with whatever approach they have. This is the best idea for a follow-up activity: it has some chance of stimulating research but is not particularly coordinated or focused. The WGCM has gone ahead with their model-comparison activity (which does not particularly progress the issue) that may culminate in results being reported at the CLIVAR science conference in June 2004, but there is no special programmatic focus on the topics of climate feedback or sensitivity at this conference. The IPCC is organizing a workshop for April 2004 on climate sensitivity. While trying to encourage some analysis activity based on the Web-collection of data, GRP will examine the results from these other meetings and then plan a follow-on workshop at which analysis results will be examined, possibly in late 2004 or early 2005.

Working Groups

WGDMA: The first meeting of the Global Energy and Water Experiment (GEWEX) Radiation Panel's (GRP) Working Group on Data Management and Analysis (WGDMA) was held at the National Climatic Data Center (NCDC) of the National Oceanographic and Atmospheric Administration (NOAA) in Asheville, North Carolina, USA, on 12-16 May 2003. This working group is formed from the data management groups of all of the GEWEX data projects under the purview of the GRP: the International Satellite Cloud Climatology Project (ISCCP), the Surface Radiation Budget project (SRB) and the Baseline Surface Radiation Network (BSRN), the Global Precipitation Climatology Project (GPCP) and the Global Precipitation Climatology Center (GPCC), and the Global Aerosol Climatology Project (GACP).

The first actions to increase collaboration among GRP projects include specific actions to: (1) begin collecting validation datasets that separate liquid and solid precipitation, separating the high-time resolution precipitation data using a global atmospheric temperature dataset and investigating the feasibility of GPCP processing of the ISCCP B1 radiance dataset to extend the daily-resolution product back to 1983, (2) working on the design for a dataset that merges (at first) all the GRP monthly-mean global products (possibly including some additional atmospheric and surface property datasets), and (3) compiling a list of statistical analysis methods to be applied to all of the GRP data products.

WGDMA/GRP proposes (seeking endorsement from the GEWEX SSG and WCRP JSC) to undertake assessments of the available global, long-term data products relevant to studying the climate-scale variations of the global energy and water cycle for input to the next IPCC report and as an appropriate precursor to WGSM plans for the re-analysis of these datasets: water vapor, clouds, precipitation and radiative fluxes (both top-of-atmosphere and surface).

Some specific cross-connecting activities that were decided on are: (1) supply of some global datasets to WEBS, (2) working with GHP WGDM to improve collection of gauge precipitation from CSEs, and (3) formulation of plans with GSWP to combine datasets more effectively in an analysis of land surface fluxes.

Issues

For the GEWEX SSG

1. Some steps have been taken to strengthen interactions of the GRP projects with WEBS/CEOP and ISLSCP/GSWP, but this issue needs further discussion and attention.

2. The Precipitation Cross-Cut could take the lead on problems of orographic precipitation and snow.

3. The best idea for a follow-up to the Feedback Workshop is to stimulate progress by compiling and releasing (on a Web site) a comprehensive, global, long-term dataset containing the main elements of the energy and water cycle for analysis (modelers would produce a similar output from their models) and organizing a workshop to compare results. Since CLIVAR does not appear to be planning anything special on the subject of climate feedbacks/sensitivity, GEWEX might consider planning a special session on this topic at the GEWEX scientific conference in 2005.

4. The current request for the lifetime of GRP projects is through 2005, but the actual funding schedules of the various data centers and projects are not consistent with this date nor any longer in synchrony. Once the WGSM plan is formulated, the GEWEX SSG should send letters early next year (through WMO) requesting extension of all GRP projects to some a new common date (2008 or 2010?).

For the JSC

1. The WGSM has been tasked by the JSC to produce an international, inter-agency plan that outlines a coherent strategy for the analysis of satellite data into global, long-term climate data products, for their cross-calibration and for their periodic assessment and re-analysis to improve homogeneity (anchored on surface monitoring networks) and to incorporate improvements based on new experimental instruments and results. GEWEX could take the lead on this.

2. Several elements of the GRP projects could be expanded in scope to support CLIVAR objectives, if some way could be found to remove obstacles from parochial viewpoints so that effective funding support could be obtained. Some examples are merging the ISCCP and surface cloud observation climatologies (ISCCP and new satellite observations will be "combined" as currently planned), merging the BSRN data record with the GEBA record (requiring re-analysis?), extending the gauge precipitation collections back in time at GPCC (SRDC?), extending the run-off data records back in time at GRD. In other words, we could build on the expertise at these "GEWEX" centers to do the work needed to bring the older data collections up to best level possible to support the longer-time-scale research of CLIVAR. CLIVAR is not doing this type of work, which has traditionally been outside the purview of GEWEX. What is the connection of this WCRP need to the activities of WCDP and GCOS (if any)?