6 22 February 2017 Centre for Environmental Data Analysis support@ceda.ac.uk A plant that utilizes the C3 carbon fixation pathway as the sole mechanism to bind CO2 before photosynthesis reactions take place. All trees are C3 type. Grasses and crops can be C3 or C4. A plant that utilizes the C4 carbon fixation pathway in which the CO2 is first bound to a compound containing four carbon atoms before photosynthesis reactions take place. All trees are C3 type. Grasses and crops can be C3 or C4. The definition of "crops" is model dependent, for example, some models may include fruit trees as crops. An area_type of "dust_aerosol" indicates that dust aerosol is present at some level in the atmospheric column above an area on the surface of the Earth. An area_type of "fire" indicates that biomass fire, either flaming, smouldering, or both, is present. All ice floating on water including lake-ice, sea-ice, ice-shelves and icebergs. An area type of "floating ice shelf" indicates where ice shelves are present. Ice shelves are the component of ice sheets that flow over the ocean. An area type of "grounded ice sheet" indicates where the ice sheet rest over bedrock and is thus grounded. It excludes ice-caps, glaciers and floating ice shelves. An area type of "ice sheet" indicates where ice sheets are present. It includes both grounded ice sheets resting over bedrock and ice shelves flowing over the ocean, but excludes ice-caps and glaciers (in contrast to land_ice, which includes all components). Floating ice excluding ice-shelves and icebergs. "Land ice" means glaciers, ice-caps, grounded ice sheets resting on bedrock and floating ice-shelves. The area occupied by type "sea_ice" is the sum of the areas of types "sea_ice_melt_pond" and "melt_pond_free_sea_ice". Pastures are assumed to be anthropogenic in origin. They include anthropogenically managed pastureland and rangeland. "Primary and secondary land" is land that is not in use as crop land or pasture land, including forests, grasslands, bare ground and vegetated wetlands. "Primary land" is land that has not undergone lulcc (land use or land cover change) due to human disturbance. "Secondary land" is land that has previously been used for agriculture, urban development or logging and has subsequently been abandoned. Reference: Hurtt et al. (2011), Climatic Change, 109 - 117, Harmonization of land-use scenarios for the period 1500–2100: 600 years of global gridded annual land-use transitions, wood harvest, and resulting secondary lands, doi: 10.1007/s10584-011-0153-2. "Primary and secondary land" refers to land use or management, rather than to specific categories of vegetation cover, e.g. the primary and secondary succession of plant species. A primary forest is a naturally regenerated forest of native species, where there are no clearly visible indications of human activities and the ecological processes are not significantly disturbed. Reference: 'Global Forest Resources Assessment: Terms and Definitions', Forestry Department of Food and Agriculture Organization (FAO) of the United Nations, Rome 2010, www.fao.org/forestry/14241-0d7b74f45b0d2cfef31599cc17e4c28cd.pdf. Deciduous trees lose their leaves seasonally, for example, during winter in high latitudes or following seasonal variations in rainfall. A primary forest is a naturally regenerated forest of native species, where there are no clearly visible indications of human activities and the ecological processes are not significantly disturbed. Reference: 'Global Forest Resources Assessment: Terms and Definitions', Forestry Department of Food and Agriculture Organization (FAO) of the United Nations, Rome 2010, www.fao.org/forestry/14241-0d7b74f45b0d2cfef31599cc17e4c28cd.pdf. Evergreen trees have leaves in all seasons. An area_type of "rain" indicates that falling rain is present at some level in the atmospheric column above an area on the surface of the Earth. The area occupied by type "sea" is equal to the sum of the areas of types "ice_free_sea" and "sea_ice". The area occupied by type "sea_ice" within a grid cell is the sum of the areas of types "sea_ice_melt_pond" and "melt_pond_free_sea_ice". Melt ponds occur on top of the existing sea ice. The area occupied by type "sea" is equal to the sum of the areas of types "ice_free_sea" and "sea_ice". The area classified as type "sea_ice" within a grid cell is unaltered when an area of type "sea_ice_melt_pond" is also present because melt ponds occur on top of the existing sea ice. A secondary forest is a forest that has been logged and has recovered naturally or artificially. Reference: 'Report of the ad hoc technical expert group on forest biological diversity', United Nations Convention on Biological Diversity, www.cbd.int/forest/definitions.shtml. Deciduous trees lose their leaves seasonally, for example, during winter in high latitudes or following seasonal variations in rainfall. A secondary forest is a forest that has been logged and has recovered naturally or artificially. Reference: 'Report of the ad hoc technical expert group on forest biological diversity', United Nations Convention on Biological Diversity, www.cbd.int/forest/definitions.shtml. Evergreen trees have leaves in all seasons. The distinction between trees and shrubs is model dependent. An area_type of "smoke" indicates that smoke aerosol is present at some level in the atmospheric column above an area on the surface of the Earth. The distinction between trees and shrubs is model dependent. All trees are C3 plant functional type. Urban land is comprised of areas where much of the land is covered by structures. Included in this category are cities, towns and villages. Reference: Anderson, J.R, E. E. Hardy, J. T. Roach and R. E. Witmer (1976), A Land Use And Land Cover Classification System For Use With Remote Sensor Data, Appendix C Land Use Definitions, Geological Survey Professional Paper 964, A revision of the land use classification system as presented in U.S. Geological Survey Circular 671, https://www.usbr.gov/lc/socal/reports/SMappend_C.pdf. An area_type of "volcanic_ash_cloud" indicates that volcanic ash aerosol is present at some level in the atmospheric column above an area on the surface of the Earth.