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1. Thermal infrared dust optical depth and coarse-mode effective diameter over oceans retrieved from collocated MODIS and CALIOP observations

   https://doi.org/10.5194/acp-23-8271-2023  

   Zheng, Jianyu; Zhang, Zhibo; Yu, Hongbin; Garnier, Anne; Song, Qianqian; Wang, Chenxi; Di Biagio, Claudia; Kok, Jasper F.; Derimian, Yevgeny; Ryder, Claire (January 2023, Atmospheric Chemistry and Physics)

   Abstract. In this study, we developed a novel algorithm based on the collocatedModerate Resolution Imaging Spectroradiometer (MODIS) thermal infrared (TIR)observations and dust vertical profiles from the Cloud–Aerosol Lidar withOrthogonal Polarization (CALIOP) to simultaneously retrieve dust aerosoloptical depth at 10 µm (DAOD10 µm) and the coarse-mode dusteffective diameter (Deff) over global oceans. The accuracy of theDeff retrieval is assessed by comparing the dust lognormal volumeparticle size distribution (PSD) corresponding to retrieved Deff withthe in situ-measured dust PSDs from the AERosol Properties – Dust(AER-D), Saharan Mineral Dust Experiment (SAMUM-2), and Saharan Aerosol Long-Range Transport and Aerosol–Cloud-InteractionExperiment (SALTRACE) fieldcampaigns through case studies. The new DAOD10 µm retrievals wereevaluated first through comparisons with the collocated DAOD10.6 µmretrieved from the combined Imaging Infrared Radiometer (IIR) and CALIOPobservations from our previous study (Zheng et al., 2022). The pixel-to-pixelcomparison of the two DAOD retrievals indicates a good agreement(R∼0.7) and a significant reduction in (∼50 %) retrieval uncertainties largely thanks to the better constraint ondust size. In a climatological comparison, the seasonal and regional(2∘×5∘) mean DAOD10 µm retrievals basedon our combined MODIS and CALIOP method are in good agreement with the twoindependent Infrared Atmospheric Sounding Interferometer (IASI) productsover three dust transport regions (i.e., North Atlantic (NA; R=0.9),Indian Ocean (IO; R=0.8) and North Pacific (NP; R=0.7)). Using the new retrievals from 2013 to 2017, we performed a climatologicalanalysis of coarse-mode dust Deff over global oceans. We found thatdust Deff over IO and NP is up to 20 % smaller than that over NA.Over NA in summer, we found a ∼50 % reduction in the numberof retrievals with Deff>5 µm from 15 to35∘ W and a stable trend of Deff average at 4.4 µm from35∘ W throughout the Caribbean Sea (90∘ W). Over NP inspring, only ∼5 % of retrieved pixels with Deff>5 µm are found from 150 to 180∘ E, whilethe mean Deff remains stable at 4.0 µm throughout eastern NP. To the best of our knowledge, this study is the first to retrieve both DAOD andcoarse-mode dust particle size over global oceans for multiple years. Thisretrieval dataset provides insightful information for evaluating dustlongwave radiative effects and coarse-mode dust particle size in models. 

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2. Robust observations of land-to-atmosphere feedbacks using the information flows of FLUXNET

   https://doi.org/10.1038/s41612-019-0094-4  

   Gerken, Tobias; Ruddell, Benjamin L.; Yu, Rong; Stoy, Paul C.; Drewry, Darren T. (October 2019, npj Climate and Atmospheric Science)

   Abstract Feedbacks between atmospheric processes like precipitation and land surface fluxes including evapotranspiration are difficult to observe, but critical for understanding the role of the land surface in the Earth System. To quantify global surface-atmosphere feedbacks we use results of a process network (PN) applied to 251 eddy covariance sites from the LaThuile database to train a neural network across the global terrestrial surface. There is a strong land–atmosphere coupling between latent (LE) and sensible heat flux (H) and precipitation (P) during summer months in temperate regions, and betweenHandPduring winter, whereas tropical rainforests show little coupling seasonality. Savanna, shrubland, and other semi-arid ecosystems exhibit strong responses in their coupling behavior based on water availability. Feedback couplings from surface fluxes toPpeaks at aridity (P/potential evapotranspiration ET_p) values near unity, whereas coupling with respect to clouds, inferred from reduced global radiation, increases asP/ET_papproaches zero. Spatial patterns in feedback coupling strength are related to climatic zone and biome type. Information flow statistics highlight hotspots of (1) persistent land–atmosphere coupling in sub-Saharan Africa, (2) boreal summer coupling in the central and southwestern US, Brazil, and the Congo basin and (3) in the southern Andes, South Africa and Australia during austral summer. Our data-driven approach to quantifying land atmosphere coupling strength that leverages the global FLUXNET database and information flow statistics provides a basis for verification of feedback interactions in general circulation models and for predicting locations where land cover change will feedback to climate or weather. 

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3. Where Dust Comes From: Global Assessment of Dust Source Attributions With AeroCom Models

   Kim, Dongchul; Chin, Mian; Schuster, Greg; Yu, Hongbin; Takemura, Toshihiko; Tuccella, Paolo; Ginoux, Paul; Liu, Xiaohong; Shi, Yang; Matsui, Hitoshi; et al (August 2024, Journal of Geophysical Research: Atmospheres)

   Abstract The source of dust in the global atmosphere is an important factor to better understand the role of dust aerosols in the climate system. However, it is a difficult task to attribute the airborne dust over the remote land and ocean regions to their origins since dust from various sources are mixed during long‐range transport. Recently, a multi‐model experiment, namely the AeroCom‐III Dust Source Attribution (DUSA), has been conducted to estimate the relative contribution of dust in various locations from different sources with tagged simulations from seven participating global models. The BASE run and a series of runs with nine tagged regions were made to estimate the contribution of dust emitted in East‐ and West‐Africa, Middle East, Central‐ and East‐Asia, North America, the Southern Hemisphere, and the prominent dust hot spots of the Bodélé and Taklimakan Deserts. The models generally agree in large scale mean dust distributions, however models show large diversity in dust source attribution. The inter‐model differences are significant with the global model dust diversity in 30%–50%, but the differences in regional and seasonal scales are even larger. The multi‐model analysis estimates that North Africa contributes 60% of global atmospheric dust loading, followed by Middle East and Central Asia sources (24%). Southern hemispheric sources account for 10% of global dust loading, however it contributes more than 70% of dust over the Southern Hemisphere. The study provides quantitative estimates of the impact of dust emitted from different source regions on the globe and various receptor regions including remote land, ocean, and the polar regions synthesized from the seven models. 

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4. Alpine ice core record of large changes in dust, sea-salt, and biogenic aerosol over Europe during deglaciation

   https://doi.org/10.1093/pnasnexus/pgaf186  

   Legrand, Michel; McConnell, Joseph R; Preunkert, Susanne; Wachs, David; Chellman, Nathan J; Rehfeld, Kira; Bergametti, Gilles; Wensman, Sophia M; Aeschbach, Werner; Oberthaler, Markus K; et al (June 2025, PNAS Nexus)

   Romanowicz, Barbara (Ed.)

   Aerosol radiative forcing is an important but often poorly understood component of regional climate. While glacier ice contains the most detailed archives of past atmospheric aerosol composition and temperature, no well-preserved ice records extending into the last climatic transition have been reported for the historically important European region. Here, we use an Alpine ice core to document changes in European aerosols and climate from the end of the last glacial age (LGA) through the Holocene. The core was drilled on a glacier dome in the French Alps called the Dôme du Goûter (DDG), and it provides a stratigraphically intact record of aerosol and climate extending to at least 12 kyears (ky) before present. Although dating near the base of the glacier is not well constrained, the oldest DDG ice layers reflect glacial conditions in western Europe during the LGA. In addition to changes in atmospheric transport, increased sea-salt and dust deposition in western Europe recorded in the LGA ice suggest enhanced westerly winds and more active dust sources, possibly including North Africa. Deposition of terrestrial biogenic indicators during the cold LGA climate was lower, however, consistent with strongly reduced European vegetation. The DDG record of terrestrial biogenic emissions also suggests a decline of European forests throughout the Holocene, resulting from deterioration of climatic conditions and more recently from establishment of the first agricultural societies. The pronounced changes in atmospheric aerosol recorded in Alpine ice imply large variations in aerosol radiative forcing in western Europe during the last 12 ky. 

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5. A climatic dipole drives short- and long-term patterns of postfire forest recovery in the western United States

   https://doi.org/10.1073/pnas.2007434117  

   Littlefield, Caitlin E.; Dobrowski, Solomon Z.; Abatzoglou, John T.; Parks, Sean A.; Davis, Kimberley T. (November 2020, Proceedings of the National Academy of Sciences)

   null (Ed.)

   Researchers are increasingly examining patterns and drivers of postfire forest recovery amid growing concern that climate change and intensifying fires will trigger ecosystem transformations. Diminished seed availability and postfire drought have emerged as key constraints on conifer recruitment. However, the spatial and temporal extent to which recurring modes of climatic variability shape patterns of postfire recovery remain largely unexplored. Here, we identify a north–south dipole in annual climatic moisture deficit anomalies across the Interior West of the US and characterize its influence on forest recovery from fire. We use annually resolved establishment models from dendrochronological records to correlate this climatic dipole with short-term postfire juvenile recruitment. We also examine longer-term recovery trajectories using Forest Inventory and Analysis data from 989 burned plots. We show that annual postfire ponderosa pine recruitment probabilities in the northern Rocky Mountains (NR) and the southwestern US (SW) track the strength of the dipole, while declining overall due to increasing aridity. This indicates that divergent recovery trajectories may be triggered concurrently across large spatial scales: favorable conditions in the SW can correspond to drought in the NR that inhibits ponderosa pine establishment, and vice versa. The imprint of this climatic dipole is manifest for years postfire, as evidenced by dampened long-term likelihoods of juvenile ponderosa pine presence in areas that experienced postfire drought. These findings underscore the importance of climatic variability at multiple spatiotemporal scales in driving cross-regional patterns of forest recovery and have implications for understanding ecosystem transformations and species range dynamics under global change. 

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