Climate Sciences

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Assessing long-distance atmospheric transport of soilborne plant pathogens
Brodsky, Hannah K.; Calderón, Rocío; Hamilton, Douglas S.; Li, Longlei; Miles, Andrew; Pavlick, Ryan; Gold, Kaitlin M.; Crandall, Sharifa G.; Mahowald, Natalie (2023)
These files contain data supporting results in Brodsky et al. Assessing Long-Distance Atmospheric Transport of Soilborne Plant Pathogens. In Brodsky et al. we modify an atmospheric transport model to simulate the global transport of a plant pathogenic soilborne fungus. Pathogenic fungi are a leading cause of crop disease and primarily spread through microscopic, durable spores adapted differentially for both persistence and dispersal via soil, animals, water, and/or the atmosphere. Computational Earth System Models and air pollution models have been used to simulate atmospheric spore transport for aerial-dispersal-adapted (airborne) rust diseases, but the importance of atmospheric spore transport for soil-dispersal- adapted (soilborne) diseases remains unknown. While a few existing simulation studies have focused on intracontinental dispersion, transoceanic and intercontinental atmospheric transport of soilborne spores entrained in agricultural dust aerosols is understudied and may contribute to disease spread. This study adapts the Community Atmosphere Model, the atmospheric component of the Community Earth System Model, to simulate the global transport of the plant pathogenic soilborne fungus Fusarium oxysporum (F. oxy). Our sensitivity study assesses the model’s accuracy in long-distance aerosol transport and the impact of deposition rate on long- distance spore transport in Summer 2020 during a major dust transport event from Northern Sub- Saharan Africa to the Caribbean and southeastern U.S. We find that decreasing wet and dry deposition rates by an order of magnitude improves representation of long-distance, trans- Atlantic dust transport. Simulations also suggest that a small number of viable spores can survive trans-Atlantic transport to be deposited in agricultural zones. This number is dependent on source spore parameterization, which we improved through a literature search to yield a global map of F. oxy spore distribution in source agricultural soils. Using this map and aerosol transport modeling, we show how viable spore numbers in the atmosphere decrease with distance traveled and offer a novel danger index for viable spore deposition in agricultural zones. Our work finds that intercontinental transport of viable spores to cropland is greatest between Eurasia, North Africa, and Sub-Saharan Africa, suggesting that future observational studies should concentrate on these regions.
Dataset for Intrinsic Century-Scale Variability in Tropical Pacific Sea Surface Temperatures and their Influence on Western US Hydroclimate
Evans, Colin P.; Coats, Sloan; Carrillo, Carlos M.; Li, Xiaolu; Alessi, Marc J.; Herrera, Dimitris A.; Benton, Brandon N.; Ault, Toby R. (2022-11-22)
These files contain the data supporting the results of the Evans, et al, 2022 paper, “Intrinsic Century Scale Variability in Tropical Pacific Sea Surface Temperatures and their Influence on Southwestern US Hydroclimate”. In Evans et al 2022, we found: Hydroclimate variability of the southwest United States (SWUS) is influenced by the tropical Pacific Ocean, particularly through the teleconnection to El Niño/Southern Oscillation (ENSO), which is expected to be altered by climate change. Natural variability in this teleconnection has not been robustly quantified, complicating the detection of anthropogenic climate change. Here, we use a linear inverse model (LIM) to quantify natural variability in the ENSO-SWUS teleconnection. The LIM yields realistic teleconnection patterns with century-scale variability comparable to simulations from the Last Millennium Ensemble project and the Climate Model Intercomparison Project Phases 5 and 6. The variability quantified by the LIM illuminates two aspects of our understanding of ENSO and its impacts: the inherent statistics of the observable system can produce century-long periods with a wide range of correlations to SWUS hydroclimate, including nonsignificant correlations, and thus that detecting changes in ENSO-related hydroclimate variability is challenging in a changing climate.
Data from: Short-term impacts of 2017 western North American wildfires on meteorology, the atmosphere’s energy budget, and premature mortality
Bernstein, Diana; Hamilton, Douglas S.; Krasnoff, Rosalie; Mahowald, Natalie M.; Connelly, David S.; Tilmes, Simone; Hess, Peter G. (2021-05-25)
Western North American fires have been increasing in magnitude and severity over the last few decades. The complex coupling of fires with the atmospheric energy budget and meteorology creates short-term feedbacks on regional weather altering the amount of pollution to which Americans are exposed. Using a combination of model simulations and observations, this study shows that the severe fires in the summer of 2017 increased atmospheric aerosol concentrations leading to a cooling of the air at the surface, reductions in sensible heat fluxes, and a lowering of the planetary boundary layer height over land. This combination of lower-boundary layer height and increased aerosol pollution from the fires reduces air quality. We estimate that from start of August to end of October 2017, ~400 premature deaths occurred within the western US as a result of short-term exposure to elevated PM2.5 from fire smoke. As North America confronts a warming climate with more fires the short-term climate and pollution impacts of increased fire activity should be assessed within policy aimed to minimize impacts of climate change on society.
Data from: Antecedent Soil Moisture Conditions Determine Land-Atmosphere Coupling Drought Risk in the Northeastern United States
Alessi, M. J.; Herrera, D. A.; Evans, C.P.; DeGaetano, A. T.; Ault, T. R. (2021-04-05)
Strengthened land-atmosphere coupling in the northeastern United States (NEUS), accompanied by a positive soil moisture-rainfall feedback, may lead to more short-term or flash droughts. Coupling between the land and atmosphere emerges when low soil moisture values limit surface latent heat flux, or evapotranspiration, so that a majority of absorbed solar radiation is emitted from the surface as sensible heat. In this study, the Weather Research and Forecasting model (WRF) was run with four prescribed soil moisture levels across seven years to elucidate the strength of land-atmosphere coupling under potential, future soil moisture states in the NEUS. Under drier soil moisture conditions, land-atmosphere coupling strengthens, and a positive soil moisture-precipitation feedback develops in all years despite differences in synoptic influx of moisture. As snowpack decreases and evaporative demand increases, antecedent soil moisture conditions may become drier in future summers over the NEUS, resulting in the more frequent development of flash droughts. This dataset supports the findings of this publication.
Model output datasets for: Constraining the atmospheric limb of the plastic cycle
Brahney, Janice; Mahowald, Natalie; Prank, Marje; Cornwell, Gavin; Klimont, Zbigniew; Matsui, Hitoshi; Prather, Kim (2021-03-23)
Microplastic particles and fibers generated from the breakdown of mismanaged waste are now so prevalent that they cycle through the Earth in a manner akin to global biogeochemical cycles. In modeling the atmospheric limb of the plastic cycle, we show that most atmospheric plastics are derived from the legacy production of plastics from waste that has continued to build up in the environment. Roads dominated the sources of microplastics to the western U.S., followed by marine, agriculture, and dust emissions generated downwind of population centers. At the current rate of increase of plastic production (~4% per year), understanding the sources and consequences of microplastics in the atmosphere should be a priority.
Atmospheric mean mineral aerosol abundance and direct radiative effect by dust for models and cases described in Li et al. (2020)
Li, Longlei; Mahowald, Natalie M.; Miller, Ron L.; García-Pando, Carlos Pérez; Klose, Martina; Hamilton, Douglas S.; Ageitos, Maria Gonçalves; Ginoux, Paul; Balkanski, Yves; Green, Robert O.; Kalashnikova, Olga; Kok, Jasper F.; Obiso, Vincenzo; Paynter, David; Thompson, David R. (2020)
The large uncertainty in mineral dust direct radiative effect (DRE) hinders projections of future climate change due to anthropogenic activity. Resolving modelled dust mineral-speciation allows for spatially and temporally varying refractive indices consistent with dust aerosol composition. Here, for the first time, we quantify the range in dust DRE at the top of the atmosphere (TOA) due to current uncertainties in the surface soil mineralogical content using a dust mineral-resolving climate model. We propagate observed uncertainties in soil mineral abundances from two soil mineralogy atlases along with the optical properties of each mineral into the DRE and compare the resultant range with other sources of uncertainty across six climate models. The shortwave DRE responses region-specifically to the dust burden depending on the mineral speciation and underlying shortwave surface albedo; positively when the regionally averaged annual surface albedo is larger than 0.28, and negatively otherwise. Among all minerals examined, the shortwave TOA DRE and single scattering albedo at the 0.44-0.63 µm band are most sensitive to the fractional contribution of iron oxides to the total dust composition. The global net (shortwave plus longwave) TOA DRE is estimated to be within -0.23 to +0.35 W m-2. Approximately 97% of this range relates to uncertainty in the soil abundance of iron oxides. Representing iron-oxide with solely hematite optical properties leads to an overestimation of shortwave DRE by +0.10 W m-2 at the TOA, as goethite is not as absorbing as hematite in the shortwave spectrum range. Our study highlights the importance of iron oxides to the shortwave DRE: they have a disproportionally large impact on climate considering their small atmospheric mineral mass fractional burden (~2%). An improved description of iron oxides, such as those planned in the Earth Surface Mineral Dust Source Investigation (EMIT), is thus essential for more accurate estimates of the dust DRE. This dataset supports this study.
Data from: Anthropogenic Perturbations to the Atmospheric Molybdenum Cycle
Wong, Michelle Y.; Rathod, Sagar D.; Howarth, Robert W.; Marino, Roxanne; Alastuey, Andres; Artaxo, Paulo; Barraza, Francisco; Beddow, D.C.S.; Bond, Tami; Chellam, Shankar; Chen, Yu-Cheng; Chen, Ying; Chien, Chia-Te; Cohen, David D.; Connelly, David; Dongarra, Gaetano; Gomez, Dario; Hand, Jenny; Harrison, R.M.; Hopke, Philip; Hueglin, Christoph; Husain, Liaquat; Kuang, Yuan-wen; Lambert, Fabrice; Liang, James; Li, Longleino; Losno, Remi; Maenhaut, Willy; Milando, Chad; Monteiro, Maria Inês Couto; Morera Gómez, Yasser; Paytan, Adina; Prospero, Joesph S.; Querol, Xavier; Rodriguez, Sergio; Smichowski, Patricia; Varrica, Daniela; Xiao, Yi-hua; Xu, Yangjunjie; Mahowald, Natalie M. (2021)
Molybdenum (Mo) is an essential trace element that is, important for terrestrial and aquatic ecosystems, as it is required for biological nitrogen fixation and uptake. Mo is carried in particles to the atmosphere from sources such as desert dust, sea spray, and volcanoes resulting in losses and sources to different ecosystems. Atmospheric Mo deposition is essential on long time scales for soils which have lost Mo due to soil weathering, with consequences for nitrogen cycling. Anthropogenic changes to the Mo cycle from combustion, motor vehicles, and agricultural dust, are likely to be large, and have more than doubled sources of Mo to the atmosphere. Locally, anthropogenic changes to Mo in industrialized regions can represent a 100‐fold increase in deposition, and may affect nitrogen cycling in nitrogen‐limited ecosystems. This dataset supports these findings.
Data from: Importance of Uncertainties in the Spatial Distribution of Pre‐Industrial Wildfires for Estimating Aerosol Radiative Forcing
Wan, Jessica S.; Hamilton, Douglas S.; Mahowald, Natalie M. (2021-02-09)
This dataset supports the findings of the publication described here: Fires are a key driver of changes to physical landscapes, biogeochemical cycles, and climate on a variety of spatial and temporal scales. In particular, the aerosol particles emitted in fire smoke influence regional and global climate by altering the atmospheric energy budget via interactions with solar radiation and by modifying clouds. In this study, we quantify the aerosol radiative impacts on climate from changing the location and strength of pre‐industrial fires for four different emission representations. We find that changing only the location of pre‐industrial fires contributes an additional 25% uncertainty to the estimated range of radiative impacts calculated. Thus, it is important to consider not only changes in the magnitude of fires, but in which regions past fires are occurring when estimating human‐induced changes to climate and the Earth System.
Data from: Recent (1980-to-2015) trends and variability in daily-to-interannual soluble iron deposition from dust, fire, and anthropogenic sources
Hamilton, Douglas S.; Scanza, Rachel A.; Rathod, Sagar D.; Bond, Tami C.; Kok, Jasper F.; Li, Longlei; Matsui, Hitoshi; Mahowald, Natalie M. (2020-09-01)
The iron cycle is a key component of the Earth system. Yet how variable the atmospheric flux of soluble (bioaccessible) iron into oceans is, and how this variability is modulated by human activity and a changing climate, is not well-known. Quantifying soluble iron daily-to-interannual deposition variability from all major iron sources, not only dust, will advance quantification of changes in marine biogeochemistry in response to the continuing human perturbation to the Earth System. The data in this repository relates to Hamilton et al. (2020) which characterized Satellite Era (1980-to-2015) daily-to-interannual modelled soluble iron emission and deposition variability from both pyrogenic (fires and anthropogenic combustion) and dust sources. Multi-model monthly mean soluble iron and dust deposition data is provided, as presented in the main manuscript. Also provided is daily deposition data for CAM6. A new transient monthly varying (1980 to 2015) anthropogenic (sum of combustion and metal smelting) iron emission data set was developed for this study, that data set is also included here.
Annual mean soluble iron deposition and ocean BGC response for each case in Hamilton et al. (2020)
Hamilton, Douglas S; Moore, Keith; Arneth, Almut; Bond, Tami; Carslaw, Ken S; Hanston, Stijn; Ito, Akinori; Kaplan, Jed O; Lindsay, Keith; Nieradzik, Lars P; Rathod, Sagar D; Scanza, Rachel A; Mahowald, Natalie M (2020-02-25)
Iron can be a growth‐limiting nutrient for phytoplankton, modifying rates of net primary production, nitrogen fixation, and carbon export, highlighting the importance of new iron inputs from the atmosphere. The bioavailable iron fraction depends on the emission source and the dissolution during transport. The impacts of anthropogenic combustion and land use change on emissions from industrial, domestic, shipping, desert, and wildfire sources suggest that Northern Hemisphere soluble iron deposition has likely been enhanced between 2 to 68% over the Industrial Era. If policy and climate follow the intermediate Representative Concentration Pathway 4.5 trajectory then results suggest that Southern Ocean (>30°S) soluble iron deposition would be enhanced between 63 to 95% by 2100. Marine net primary productivity and carbon export within the open ocean are most sensitive to changes in soluble iron deposition in the Southern Hemisphere; this is predominantly driven by fire rather than dust iron sources. Changes in iron deposition cause large perturbations to the marine nitrogen cycle, up to 70% increase in denitrification and 15% increase in nitrogen fixation, but only modestly impacts the carbon cycle and atmospheric CO2 concentrations (1‐3 ppm). Regionally, primary productivity increases due to increased iron deposition are often compensated by offsetting decreases downstream corresponding to equivalent changes in the rate of phytoplankton macronutrient uptake, particularly in the equatorial Pacific. These effects are weaker in the Southern Ocean, suggesting that changes in iron deposition in this region dominates the global carbon cycle and climate response.

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