A new global archive of soil type and land cover data derived for use in GCM climate mode--is (-;scribe1 The data are archived at a resolution of 1" latitude X 1" longitude. The method of construction of the component data sets is given together with 'reliability estimates'. The soils data form the only published data set designed specifically for use in climate studies. The land cover data are compatible with the soils data, forming a coherent and complete data set and seem to be comparable with other land cover information. Recommendations are made about combining and coarsening the data to the grid of any general circulation climate model. Methods of parameterizing surface radiative and hydrological properties in climate models are proposed.

The climate system is driven, primarily, by energy absorbed at the surface. Surface albedo sensitivity is incorporated into all types of climate models, and changes can lead to large feedback effects. For example, alterations in the extent and/or state of the cryosphere and large-scale modification of vegetation cause significant perturbations in climate model results. The specification of surface albedo in general circulation climate models (GCM's) differs. An improved and agreed surface albedo data set is urgently required for climate modeling. It is likely that the most appropriate means of achieving consistent and credible surface albedos is by using well-designed satellite surveillance to augment global inventories of soils and vegetation. However, retrieval of surface albedo values for all sky and surface conditions from satellite observations is difficult. Atmospheric distortion is especially hard to remove. Some of the sensitivity of GCM's to surface albedo values may be the result of inadequate parameterization of other climatic components. The accuracy of information demanded by climate modelers could be reduced and made more consistent. Recommendations are made for the implementation of a new global scale observational program with the aim of providing surface albedo data at an accuracy of ___ 0.05 within 5-10 years. Immediate initiation is urged.

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A series of sensitivity experiments has been conducted using a version of the NCAR Community Climate Model (CCM) and a complementary zero-dimensional land surface model in order to investigate the sensitivity of the models to surface process parameteri7ations in northern high latitudes. The study was motivated by anomalously high surface temperatures at these latitudes in a control simulation with the CCM. The effects of perturbing the maximum vegetation cover, distribution of the roots within the active soil layer, the depth of the active soil layer, soil albedo, and of maintaining a fully saturated upper and active soil layer were explored. Little response occurred in either model when the depth of the soil or the root distribution was altered. Increasing the percentage of ground covered by vegetation increased the canopy air temperature but generally reduced soil temperatures in the zero-dimensional model. However, in the CCM integration the surface air temperature increased over most of the region for this change. This response seems to be due to the high level of precipitation during the three-dimensional integration and is similar to one of the zero-dimensional computations in which a large rainfall event was prescribed on the second day of the 10 day integration. Maintaining the moisture contents of both soil layers at their capacity caused a decrease in soil temperatures at most locations in the CCM and in the zerodimensional model once the soil in the control began to dry out. Increasing the soil albedo also produced soil and surface air cooling in both models. All the integrations underlined the considerable sensitivity of the land surface parameterization scheme to the instantaneous and preceding soil moisture conditions. Reduction in surface temperatures achieved was significantly less than the original discrepancy between CCM temperatures and observations. Part of the discrepancy could be caused by unrepresentative observational data and a model bias toward high levels of net surface radiation. In addition, preliminary calculations suggest that explicit inclusion of permafrost may be necessary before a fully satisfactory representation of the tundra land-surface climate can be achieved. This conclusion may be important for C0,-induced climate-change studies.

It is apparent that the surface types and percentage covers recorded in any land use data archive will be a function of both the scale of the source maps and the resolution of the archive itself. This paper illustrates this fundamental cartographic fact in the context of climate modelling with a simple investigation in which the percentage cover of seven basic land use classes was calculated using national survey maps with a scale of 1:50 000. The results were compared with similar computations using maps of other scales and with the information contained in two recently published global archives of land surface type. The assessed extent of urban areas is a function of the base map type used. The existence of open water and swamp/marsh areas is not recorded in coarse resolution data archives even when these areas cover 15% of a 1 ~ x 1 ~ grid element. Both these results are features of the data aggregation problem fundamental to geographical representation. This problem cannot be removed simply by producing global data sets at alternative resolutions. A more careful assessment of the sensitivity of models to aspects of the information archive is required.