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Wildfires and agricultural burning generate seemingly increasing smoke aerosol emissions, impacting societal and natural ecosystems. To understand smoke's effects on climate and public health, we analyzed the spatiotemporal distribution of smoke aerosols, focusing on two major light-absorbing components, black carbon (BC) and brown carbon (BrC) aerosols. Using NASA's Earth Polychromatic Imaging Camera (EPIC) instrument aboard the NOAA's Deep Space Climate Observatory (DSCOVR) spacecraft, we inferred BC and BrC volume fractions and particle mass concentrations based on spectral absorption provided by the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm with 1-2 hours temporal resolution and ~10 km spatial resolution over North America and Central Africa. Our analyses of regional smoke properties reveal distinct characteristics for aerosol optical depth (AOD) at 443 nm, spectral single scattering albedo (SSA), aerosol layer height (ALH), and BC and BrC amounts. Smoke cases in North America show extremely high AOD up to 6, with elevated ALH (6-7 km) and significant BrC components up to 250 mg/m2 along the transport paths, whereas the smoke aerosols in Central Africa exhibited stronger light absorption (i.e., lower SSA) and lower AOD, resulting in higher BC mass concentrations and similar BrC mass concentrations than the cases in North America. Seasonal burning source locations in Central Africa following the seasonal shift of Inter Tropical Convergence Zone and diurnal variations in smoke amounts were also captured. Comparison of retrieved AOD443, SSA443, SSA680, and ALH with collocated AERONET and CALIOP measurements shows agreement with rmse of 0.2, 0.03-0.04, 0.02-0.04, and 0.8-1.3 km, respectively. Analysis of spatiotemporally average reveals distinct geographical characteristics in smoke properties closely linked to burning types and meteorological conditions. Forest wildfires over western North America generated smoke with small BC volume fraction of 0.011 and high ALH with large variability (2.2 ± 1.2 km), whereas smoke from wildfires and agricultural burning over Mexico region shows more absorption and low ALH. Smoke from savanna fires over Central Africa has the most absorption with high BC volume fraction (0.015) and low ALH with small variation (1.8 ± 0.6 km) among the analyzed regions. Tropical forest smoke was less absorbing and had a high variance in ALH. We also quantify the estimation uncertainties related to the assumptions of BC and BrC refractive indices. The MAIAC EPIC smoke properties with BC and BrC volume and mass fractions and assessment of layer height provide observational constraints for radiative forcing modeling and air quality and health studies. [ABSTRACT FROM AUTHOR]

Isotopic composition of precipitation in the mountains of four Central Asian countries (Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan) was measured using 908 event-based precipitation samples collected at eight sites in 2019-2021, and 7 monthly samples from Dushanbe (Tajikistan) thereby filling a gap in stable isotope data for the region. Regional and seasonal patterns of δ18O, δD and D-excess were investigated. Local Meteoric Water Lines (LMWL) derived using seven regression methods using both non-weighted and weighted precipitation. It is recommended that the non-weighted Ordinary Least Squares Regression (OLSR) and Reduced Major Axis Regression (RMA) methods can be applied across the region except in summer, when the Precipitation-Weighted Least Squares Regression (PWLSR) method is recommended. An atmospheric back trajectory analysis and a mixing model were applied in combination for the first time, using the δ18O, δD and D-excess data, to identify the atmospheric moisture source regions and quantify the relative importance. The main distant sources were the Black and Caspian Seas region, Iran - eastern Mediterranean, and northern Kazakhstan - Siberia. The recycled moisture from the irrigated lower reaches of the Amu Darya and Syr Darya rivers, and from the study catchments, accounted for 29-71% of the atmospheric moisture reaching the observation points. In spring, summer and winter, in the Chon- Kyzyl-Suu catchment, up to 85% of the precipitation was estimated to be derived from local re-evaporation, most likely from Lake Issyk Kul. These findings highlight the importance of moisture from terrestrial sources, especially irrigated land, in precipitation formation in Central Asia. [ABSTRACT FROM AUTHOR]

Cloud condensation nuclei (CCN) are mediators of aerosol-cloud interactions (ACI), contributing to the largest uncertainties in the understandings of global climate change. We present a novel remote sensing-based algorithm that quantifies the vertically-resolved CCN number concentrations (NCCN) using aerosol optical properties measured by a multiwavelength lidar. The algorithm considers five distinct aerosol subtypes with bimodal size distributions. The inversion used the look-up tables developed in this study, based on the observations from the Aerosol Robotic Network to efficiently retrieve optimal particle size distributions from lidar measurements. The method derives dry aerosol optical properties by implementing hygroscopic enhancement factors to lidar measurements. The retrieved optically equivalent particle size distributions and aerosol type dependent particle composition are utilized to calculate critical diameter using the κ-Köhler theory and NCCN at six supersaturations ranging from 0.07% to 1.0%. Sensitivity analyses indicate that uncertainties in extinction coefficients and relative humidity greatly influence the retrieval error in NCCN. The potential of this algorithm is further evaluated by retrieving NCCN using airborne lidar from the NASA ORACLES campaign and validated against simultaneous measurements from the CCN counter. The independent validation with robust correlation demonstrates promising results. Furthermore, the NCCN has been retrieved for the first time using a proposed algorithm from spaceborne lidar - Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) - measurements. The application of this new capability demonstrates the potential for constructing a 3D CCN climatology at a global scale, which help to better quantify ACI effects and thus reduce the uncertainty in aerosol climate forcing. [ABSTRACT FROM AUTHOR]

The iron-oxide content of dust in the atmosphere and most notably its apportionment between hematite (α-Fe2O3) and goethite (α-FeOOH) are key determinants in quantifying dust's light absorption, its top of atmosphere UV radiances used for dust monitoring, and ultimately shortwave dust direct radiative effects (DRE). Hematite and goethite column mass concentrations and iron-oxide mass fractions of total dust mass concentration were retrieved from the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) measurements in the ultraviolet-visible (UV-Vis) channels. The retrievals were performed for dust-identified aerosol plumes using aerosol optical depth (AOD) and spectral imaginary refractive index provided by the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm over six continental regions (North America, North Africa, West Asia, Central Asia, East Asia, and Australia). The dust particles are represented as an internal mixture of non-absorbing host and absorbing hematite and goethite. We use the Maxwell-Garnett effective medium approximation with carefully selected complex refractive indices of hematite and goethite that produce mass fractions of iron oxides species consistent with in situ values found in the literature to derive the hematite and goethite volumetric/mass concentrations from MAIAC EPIC products. We compared the retrieved hematite and goethite concentrations with in situ dust aerosol mineralogical content measurements, as well as with published data. Our data display variations within the published range of hematite, goethite, and iron-oxide mass fractions for pure mineral dust cases. A specific analysis is presented for 15 sites over the main dust source regions. Sites in the central Sahara, Sahel, and Middle East exhibit a greater temporal variability of iron oxides relative to other sites. Niger site (13.52°N, 2.63°E) is dominated by goethite over Harmattan season with median of ~2 weight percentage (wt.%) of iron-oxide. Saudi Arabia site (27.49°N, 41.98°E) over Middle East also exhibited surge of goethite content with the beginning of Shamal season. The Sahel dust is richer in iron-oxide than Saharan and northern China dust except in Summer. The Bodélé Depression area shows a distinctively lower iron-oxide concentration (~1 wt.%) throughout the year. Finally, we show that EPIC data allow to constrain the hematite refractive index. Specifically, we select 5 out of 13 different number of hematite refractive indices widely variable in published laboratory studies by constraining the iron-oxide mass ratio to the known measured values. Provided climatology of hematite and goethite mass fractions across main dust regions of the Earth will be useful for dust shortwave DRE studies and climate modeling. [ABSTRACT FROM AUTHOR]

The current study investigates the diurnal cycle of dust loading across the global tropics, sub-tropics, and mid-latitudes by analyzing aerosol extinction and typing profiles observed by the Cloud-Aerosol Transport System (CATS) lidar aboard the International Space Station. According to the comparison with ground-based and other satellite observations, CATS aerosol and dust loading observations exhibits reasonable quality but significant day-night inconsistency. To account for this day-night inconsistency in CATS data quality, the diurnal variability in dust characteristics are currently examined separately for daytime and nighttime periods. Based on an analysis of variance analytical framework, pronounced diurnal variations in dust loading are generally uncovered during daytime periods and over terrestrial areas. The current study identifies statistically significant diurnal variability in dust loading over key dust sources, including the Bodele Depression, the West African El Djouf, Rub-al Khali Desert, and western and southern North America, confirming the previous observation-based findings regarding the diurnal cycle of dust emission and underlying meteorological processes in these regions. Significant seasonal dust diurnal variability is identified over the Iraqi and Thar deserts. The identified significant diurnal cycles in dust loading over the rainforests in Amazon and tropical southern Africa are hypothesized to be driven by enhanced dust emission due to wildfires. [ABSTRACT FROM AUTHOR]

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 +0.1 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. [ABSTRACT FROM AUTHOR]

The current study investigates the diurnal cycle of dust loading across the global tropics, sub-tropics, and mid-latitudes by analyzing aerosol extinction and typing profiles observed by the Cloud-Aerosol Transport System (CATS) lidar aboard the International Space Station. According to the comparison with ground-based and other satellite observations, CATS aerosol and dust loading observations exhibits reasonable quality and insignificant day-night inconsistency, thereby supporting the current analysis of dust diurnal cycle using CATS data. Based on an analysis of variance analytical framework, statistically significant diurnal variability in dust loading is identified over key dust sources, including the Bodélé depression, West African El Djouf, Rub-al Khali desert, and western and southern North America, confirming the previous observation-based findings regarding the diurnal cycle of dust emission and underlying meteorological processes in these regions. Insignificant annual mean dust diurnal variability is identified over the Iraqi, Thar, and Taklamakan deserts. The currently identified significant diurnal cycles in dust loading over the rainforests in Amazon and tropical southern Africa, and drylands in South America and the central Australia, are hypothesized to be driven by enhanced dust emission due to wildfires and enhanced katabatic and frontal winds, respectively. [ABSTRACT FROM AUTHOR]

Asian dust, primarily emitted from the Taklamakan and Gobi Deserts, has been reported to reach remote destinations, such as North America. However, the relative contribution of the Taklamakan and Gobi Deserts to dust loadings through long-range transport remains unaddressed in any observational study. Here, the climatology of Asian dust activation and transport is investigated using stereo observations of dust sources from the Multiangle Imaging SpectroRadiometer (MISR) instrument combined with observation-initiated trajectory modeling. MISR-derived dust injection height and dust plume motion vectors confirm the peak of dust activation and transport potential in spring over the Gobi Desert and in both spring and summer over the Taklamakan Desert. The long-range transport patterns of Asian dust, including the influence on North America through trans-Pacific transport, are assessed using extensive forward trajectories initiated by MISR dust plume observations. The trajectory analysis reveals latitude-dependent influence of dust from the Taklamakan and Gobi deserts, with Taklamakan dust dominantly affecting to the south of 50° N and Gobi dust primarily affecting to the north of 50° N in North America. The Asian dust activation and transport exhibit substantial seasonal and interannual variability, motivating future studies on the potential drivers. [ABSTRACT FROM AUTHOR]

We conceptualize aerosol radiative transfer processes arising from the hypothetical coupling of a global aerosol transport model and global numerical weather prediction model by applying the U.S. Naval Research Laboratory Navy Aerosol Analysis and Prediction System (NAAPS) and the Navy Global Environmental Model (NAVGEM) meteorological and surface reflectance fields. A unique experimental design during the 2013 NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission, allows for collocated airborne sampling by the Langley's High Spectral Resolution Lidar (HSRL), the Airborne Multi-angle Spectro Polarimetric Imager (AirMSPI), up/down SW and broadband IR radiometers, as well as NASA A-Train support from the Moderate Resolution Imaging Spectroradiometer (MODIS), to attempt direct aerosol forcing closure. The results demonstrate the sensitivity of modeled fields to aerosol radiative fluxes and heating rates, specifically in the SW forcing and heating rates, as induced in this event from transported smoke and regional urban aerosols. Limitations are identified with respect to aerosol attribution, vertical distribution and choice of optical and surface polarimetry properties, which are discussed within the context of their influence on Numerical Weather Prediction output that is particularly important as the community propels forward towards inline aerosol modelling within global forecast systems. [ABSTRACT FROM AUTHOR]

WRF-Chem simulations of aerosol seasonal variability in the San Joaquin Valley (SJV), California are evaluated by satellite and in-situ observations. Results show that the WRF-Chem model successfully captures the distribution, magnitude and variation of SJV aerosols in cold season. However, the aerosols are not well represented in warm season. Aerosol simulations in urban areas during the cold season are sensitive to model horizontal resolution, with better simulations at 4 km resolution than at 20 km resolution, mainly due to inhomogeneous distribution of anthropogenic emissions. In rural areas, the model sensitivity to grid size is rather small. Our observational analysis show that dust is a primary contributor to aerosols in the SJV, especially in the warm season. Aerosol simulations in the warm season are sensitive to parameterization of dust emission in the WRF-Chem model. The GOCART (Goddard Global Ozone Chemistry Aerosol Radiation and Transport) dust scheme produces very little dust in the SJV while the DUSTRAN (DUST TRANsport model) scheme overestimates dust emission. Vertical mixing of aerosols is not adequately represented in the model comparing to CALIPSO (Cloud-Aerosol Lidar and Infrared pathfinder Satellite Observation) aerosol extinction profiles. Improved representation of dust emission and vertical mixing are needed for better simulations of aerosols in warm season in the SJV. Aerosols generated by wild fires are not captured in the simulations with climatological fire emissions, underscoring the need of fire emission observations for operational usage. [ABSTRACT FROM AUTHOR]

Since early 2000, the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite has been acquiring data that has been used to produce aerosol optical depth (AOD) and particle property retrievals at 17.6 km spatial resolution. Capitalizing on the capabilities provided by multiangle viewing, the current operational (Version 22) MISR algorithm performs well with about 75% of MISR AOD retrievals globally falling within 0.05 or 20% × AOD of paired validation data from the ground-based Aerosol Robotic Network (AERONET). This paper describes the development and assessment of a prototype version of a higher spatial resolution, 4.4 km MISR aerosol product compared against multiple AERONET Distributed Regional Aerosol Gridded Observations Network (DRAGON) deployments around the globe. [ABSTRACT FROM AUTHOR]