REMOTE-SENSING OF THE LAND-SURFACE FOR STUDIES OF GLOBAL CHANGE - MODELS, ALGORITHMS, EXPERIMENTS

The ISLSCP Workshop was held in Columbia Maryland, 23-26 June 1992 wit h over 240 scientists and science managers attending. The goal was to assess the progress of the East decade in the areas of modeling, satel lite data algorithm development, and field experiments. This article i ncludes: 1. A review of the state and direction of biosphere-atmospher e model development and an assessment of the data needs of the models. Models covering a large range of timescales were considered: energy-w ater-carbon (seconds to seasons); carbon cycles and biogeochemistry (d ays to years); and ecological structure and function (years to millenn ia). 2. A reference to current satellite data algorithms and other glo bal data sources. The areas covered in the workshop were: near-surface meteorology, surface radiation budget, precipitation, runoff; snow an d ice, soils and soil moisture, and land cover type and land cover att ributes. These are discussed in detail in other articles in this issue . 3. A review of completed and planned major field experiments. The ma jor experiments of the last decade are summarized and the lessons note d, The participating scientists agreed on the need to rapidly assemble and circulate global data sets of variables and parameters required t o initialize, force, and validate the global biosphere-atmosphere mode ls. A prioritized list of data sets required to meet this need is set out and discussed. Lastly, initiatives taken by ISLSCP to satisfy thes e requirements are reviewed: Initiative I: Immediate Generation of Hig h Priority Global Data Sets Some essential global data sets are to be put together within 2 years and released to the community by mid-1994. These data sets will be mapped to a common spatial resolution (1 degr ees x 1 degrees) and will cover the period 1987-1988. 1. Vegetation: G lobal sets of vegetation-related parameters are to be generated with a monthly time resolution. Available AVHRR data sets are to be I used a s the basis for this effort, and algorithms will be applied to calcula te fields of cover type, phenology, FPAR, and leaf area index. These f ields can then in turn be used to infer other surface pa rameters such as roughness, albedo, biomass, etc. 2. Hydrometeorology: Global meteo rological fields retrieved from numerical reanalysis will be manipulat ed to provide near-surface forcing data sets for temperature, humidity , windspeed, etc. Observations of precipitation, runoff, and snow cove r are to be worked up into easily accessible forms. 3. Radiation Budge t: A closer interface with the International Satellite Cloud Climatolo gy Project (ISCCP) and related projects will be pursued to obtain surf ace radiation budget components at higher spatial resolutions, as well as fields of incident PAR. 4. Soils: A small project was set in place with the goal of providing a useful soil type and properties data set for use by global modelers. Initiative II: Improved, Follow-on Data S ets The data sets specified in Initiative I are to be generated within a e-year period. However, it is clear that great improvements could b e made over this first data release which must rely on pre-existing da ta sets and robust, available algorithms. Work was started to scope ou t what needs to be done to produce improved versions of all the Initia tive I data sets within 5 years, by mid-1997. Initiative III: Improved Communications within the Land Science Community Future discussions w ithin ISLSCP and between ISLSCP and other bodies will focus on the nee d to coordinate different research thrusts within the land science com munity, particularly the modeling, algorithm and field experiment work .