Abstract
Based on a recent request by the ACME leadership council, we initiated work to enable the usage of new land use datasets in ACME v1. This is important because using the Land use harmonization (LUH2) dataset, will enable ACME v1 to fulfill the entry card requirements for participating in CMIP6. To convert LUH2 dataset into a format that ACME v1 can recognize, we have produced updated land use datasets in the LUH1 format using LUH2 land use state and land use transition information. This involved mapping the thematically and spatially more detailed LUH2 land use states and transitions to the LUH1 land use states and transitions (LG-171). Our expanded land use dataset describes transition over time within a rich set of 12 land use states (up from 5 states in the land use dataset used in CMIP5). To test whether this mapping was performed adequately, we developed a full suite of diagnostics to compare the two datasets. These diagnostics include global comparisons at different times of the following metrics: net and gross transitions, land use area for different land use states, secondary age profile, increase in secondary land because of human impacts, wood clearing estimates and potential biomass and forest area estimates. Our diagnostics show that while land use at a global scale is similar in both LUH1 and LUH2, significant local differences that might impact C fluxes in ACME v1, do exist. In order to be ingested into the ACME v1 model, these land use datasets need to be translated into land cover information. We have used an existing land use translator (LUT) that was implemented as part of the iESM project (LG-172). The existing C based LUT code was tightly coupled with the iESM fortran code. Since we do not need the additional model couplings introduced in iESM, we successfully decoupled the LUT code, and used it to process the LUH2 land use data that we have already converted into LUH1 format.