11.1.1 Dr. Cihlar provided the background to the discussion of satellite data requirements. Although TOPC defined the requirements in its report (GCOS report#32; GCOS, 1997) the attempt by the Global Observing Systems Space Panel (GOSSP) to merge the requirements expressed individually by the GCOS, GTOS, and GOOS led to an extensive discussion and a proposed new framework for the input by scientific panels.
11.1.2 Dr. Cihlar described the preparatory work carried out to define TOPC requirements in a form suitable for this process. First, he proposed a new conceptual framework to facilitate unambiguous communication between earth scientists and satellite specialists. This framework (Figure 2) distinguishes between measurements and variables as understood by a satellite sensor designer, a remote sensing scientist, an earth system scientist, and the end user. These various specialists are concerned with one or more of, respectively, measured variables, ancillary variables, input variables, and target variables. Figure 2 shows the different categories, using net primary productivity as an example. So far, TOPC and other panels concentrated on defining the target variables, and appropriately so. The distinctions among the different types of variables and implicitly understood in the scientific community but they can create great confusion when communicating with non-specialists, engineers, or program managers. There is a strong need to define the terminology and then rigorously apply the definitions in all areas, otherwise confusion is unavoidable.
11.2.1 The meeting participants agreed that the proposed framework is appropriate and set out to provide specific details as required by the framework or GOSSP. These include:
11.2.2 (1) Finalisation of the lists of TOPC Target, Input, Ancillary, and Measured variables. For each of these variables, specification was established for Optimum and Threshold requirements for horizontal resolution, vertical resolution, cycle (revisit period), timeliness (time elapsed between satellite data acquisition and delivery of the derived product), and accuracy. (2) Finalisation of the definitions of Applications and of variables for the purpose of specifying TOPC satellite data requirements and allowing their traceability.
11.2.3 The work was conducted in two subgroups addressing the biosphere and cryosphere/hydrosphere, respectively. The results are provided in Annex 6.
Recommendation 23: The information in Annex VI should be used to specify satellite data requirements for climate-related terrestrial applications and to revise the data base maintained by WMO/CEOS.
11.2.4 When discussing the Applications the meeting participants pointed out the great potential impact of climate change on human health and other socio-economic aspects. These are outside the TOPC terms of reference. It was agreed to bring this issue to the attention of the GCOS/GTOS sponsors.
Recommendation 24: G3OS sponsors should clarify the extent to which health, economic and other terrestrial impact of climate change should be considered, and by whom.
Recommendation 25: While it is recognized that several Applications (presently not defined, Annex V.) are relevant mainly to other aspects of the G3OS program, all have some relevance to the terrestrial climate-related issues and TOPC should therefore be involved in their definition.
11.2.5 Although the differentiation of variables as target, input, ancillary and measured improves the clarity for easier communication with remote sensing specialists, it does not make clear the functional relations between the individual variables, nor does it reflect the complexity of these relationships for specific target variables. It was agreed that flowchart diagrams would be more appropriate for this purpose. However, the dependence of such diagrams on the algorithms and models assumed for the use of the measurements must be explicitly noted.
Recommendation 26: As part of further documentation TOPC should prepare flowcharts for key target variables.
Figure 2: Definitions of Variables for Earth Observations
