The objective of this project is to conduct a diagnostic analysis of the variations in climate that govern the characteristics of the fire season in the western United States on intra-annual through decadal and longer time scales. We propose a retrospective, model-based analysis to understand better the role of climate as a control of fire in the historical record, to evaluate the ability of a hierarchy of climate models to simulate multi-year and specific pre-ignition and contemporaneous climate associated with known fires (e.g. Yellowstone, 1998), and to examine the regional and temporal variability of western ecosystems and their fire-related vegetation variables. Our approach will rely on a combination of existing climate data sets, regional climate models, and equilibrium and dynamic biogeography/ biogeochemistry models. We will make use of archived climate and fire data sets, and produce climate and vegetation simulations using existing climate and vegetation models with which we have extensive experience. We will develop and apply equilibrium vegetation classification models to define vegetation vulnerability to fire, and ultimately, dynamic models that incorporate explicit and predictive fire and vegetation interactions on a landscape scale to achieve a better understanding of the dynamics might play a role in restoring natural ecosystems and reducing fuel loads. Our research will result in information that will be useful for improving fire forecasts from seasonal to longer time periods by quantifying climatically controlled base conditions over which fire-season weather will occur, and by providing knowledge of how antecedent conditions might be expected to enhance or suppress fire conditions. We will work collaboratively with Sue Ferguson USDA Forest Service to assess the ability of climate models to simulate a range of fire conditions over a variety of temporal and spatial scales, and, during later stages of the research, we plan to develop a methodology in cooperation with National Park System at Crater Lake in Southeastern Oregon to transfer our knowledge to the operational level.