2016 Progress Report: Effects of Changes in Climate and Land Use on U.S. Dust and Wildfire Particulate MatterEPA Grant Number: R835875
Title: Effects of Changes in Climate and Land Use on U.S. Dust and Wildfire Particulate Matter
Investigators: Mickley, Loretta J. , Jacob, Daniel J. , Kaplan, Jed
Institution: Harvard University , ARVE Research Sarl
EPA Project Officer: Chung, Serena
Project Period: January 1, 2016 through December 31, 2018
Project Period Covered by this Report: January 1, 2016 through December 31,2016
Project Amount: $719,780
RFA: Particulate Matter and Related Pollutants in a Changing World (2014) RFA Text | Recipients Lists
Research Category: Air , Climate Change
Project goals are as follows to: (1) quantify the effects of climate change and land use on dust mobilization and transport within the western United States; (2) quantify the impact of climate change on Asian dust influence over the western United States; and (3) provide fine-scale projections of wildfire smoke for the future climate in the West.
In Year 1 of the project, we made progress on goals #1 and #2.
Activities. We investigated the dominant spatial patterns of observed fine dust interannual variability in the western United States and the meteorological factors that control these patterns for each of the spring months (March-May) during 2002-2015. We then developed a prediction model to explore what may have caused the observed increase in March monthly mean fine dust concentrations in the Southwest over this time period. We describe the outcomes of these activities below.
We have also begun preparations to perform a series of simulations of the land cover model LPJLMfire at high spatial resolution (~5 km) for the western United States. These simulations will be driven by future climate and anthropogenic land cover change scenarios from CMIP5. We have so far collected data sets on future climate and anthropogenic land cover change from the CMIP5 archive and preprocessed these into a format usable for LPJ-LMfire.
Outcomes. Empirical orthogonal function (EOF) analysis suggests that 50-61% of the total variance in fine dust interannual variability across the western United States in the present-day can be explained by either (1) a uniform pattern of change across the region or (2) a dipole Northwest-Southwest pattern of change. Using correlation analyses, we identified regional precipitation and temperature as the key drivers of fine dust variability in the western United States. These variables are in turn driven by large-scale patterns in sea surface temperature and atmospheric circulation, including variations in the strength of the trans-Pacific transport of Asian dust. Consistent with previous studies, we found that March monthly mean fine dust concentrations have increased from 2002 to 2015 in the Southern California and Southwest regions by 0.09 ± 0.07 μg m-3 y-1. Using multiple linear regression analysis, we found that 76% of the variance in observed March fine dust concentrations averaged over the Southwest can be explained by a combination of two predictors: (1) the January-March (JFM) Pacific Decadal Oscillation index, which influences regional precipitation and temperature, and (2) long-term regional drought as defined by 48-month JFM Standardized Precipitation-Evapotranspiration Index (SPEI48). For Southern California, the following predictors capture 81% of the temporal variability: (1) regional monthly mean relative humidity, (2) variability in the strength of trans-Pacific transport of Asian dust during March, and (3) regional JFM SPEI48. With the Southwest projected to become drier and hotter in the coming decades due to human-caused climate change, our work suggests that the Southwest also could become increasingly dustier. Besides the effects on climate and ecosystems, this projection also has important public health and socioeconomic implications for the region, whose population is estimated to reach ~75 million by 2030, an increase of 34% relative to 2010.
In Year 2, we will focus on the following activities.
1. We are currently using the statistical model developed in Year 1 to determine the probable effects of 2000-2080 climate change on dust mobilization in the West. Our approach involves application of our model to CMIP5 climate projections. This task will focus on both trends in domestic dust emissions and trends in dust transport from Asia.
2. Using LPJ-LMfire, we will quantify the effects of near-term climate change and trends in land use on vegetation and soil variables in the western United States. Output will include present-day and future maps of leaf area indices, vegetation type, and soil type.
3. We will use the nested-grid version of GEOS-Chem to begin quantifying the effects of regional changes in climate and land use on dust concentrations in the western United States. Our approach will involve implementing LPJ land cover variables into the fine-scale GEOS-Chem and diagnosing the trends in dust mobilization and concentration in the 2000-2050 timeframe.
4. We will update present-day fire emissions at fine-scale resolution across the western United States. Here, we will extend the approach of Yue et al. (2013), using information from interagency fire reports of area burned from the national Fire and Aviation Management web application system (FAMWEB).
These activities will prepare us for Year 3, when we plan to use GEOS-Chem to calculate the effects of global change on dust mobilization and lifetime and on the impacts of changing
wildfire frequency in the West.