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Wednesday, April 11 • 1:45pm - 2:00pm
MODELLING CLIMATE AS PROCESS DRIVERS: What Are the Hard Problems for Landscape-model Projections in a Warming Climate?

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AUTHORS: Donald McKenzie*, US Forest Service; Maureen C. Kennedy, University of Washington; Erica A. Newman, University of Arizona

ABSTRACT: Predicting the future is hard. Landscape models face many obstacles and uncertainties. There are practical limits to model projections, such as missing data and limits to computing power, but we focus on three intrinsic limitations that are less tractable to expected ongoing improvements in modeling and data processing. (1) the “coarse-graining” problem: how to aggregate fine-scale processes to larger scales in an unbiased manner. (2) the “middle-number” problem: related to #1, but in particular affecting systems with enough elements to be intractable to brute force, but too few and too varied to be amenable to global averaging. (3) the “stationarity” problem: relationships that are valid in one environment, such as bioclimatic-envelope or other empirical models, or parameter choices in “process-based” models, change when projected onto future environments, such as a warming climate. In the context of landscape fire and vegetation models, we suggest approaches to each of these problems that involve explicit scaling laws that combine top-down and bottom-up perspectives of the dynamics. For example, coarse-graining, such as developing analogs to fire behavior and fire spread at broad spatial scales, requires quantitative metrics and algorithms that minimize error propagation across scales. This happens in both aggregation and “downscaling”: the latter being a way of representing the effects of emergent dynamics at broad scales using fine-scale physics. Similarly, addressing the stationarity problem involves understanding the interplay between top-down drivers (of fire) such as climate and bottom-up drivers such as ignitions, fuel patterns, and local topography. Quantitative scaling relationships are the key to moving forward with these difficult problems.

Wednesday April 11, 2018 1:45pm - 2:00pm CDT
LaSalle 1 (7th Floor)