Time-dependent entrainment of smoke presents an observational challenge for assessing aerosol–cloud interactions over the southeast Atlantic Ocean

The colocation of clouds and smoke over the southeast Atlantic Ocean during the southern African biomass burning season has numerous radiative implications, including microphysical modulation of the clouds if smoke is entrained into the marine boundary layer. NASA's ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign is studying this system with aircraft in three field deployments between 2016 and 2018. Results from ORACLES-2016 show that the relationship between cloud droplet number concentration and smoke below cloud is consistent with previously reported values, whereas cloud droplet number concentration is only weakly associated with smoke immediately above cloud at the time of observation. By combining field observations, regional chemistry–climate modeling, and theoretical boundary layer aerosol budget equations, we show that the history of smoke entrainment (which has a characteristic mixing timescale on the order of days) helps explain variations in cloud properties for similar instantaneous above-cloud smoke environments. Precipitation processes can obscure the relationship between above-cloud smoke and cloud properties in parts of the southeast Atlantic, but marine boundary layer carbon monoxide concentrations for two case study flights suggest that smoke entrainment history drove the observed differences in cloud properties for those days. A Lagrangian framework following the clouds and accounting for the history of smoke entrainment and precipitation is likely necessary for quantitatively studying this system; an Eulerian framework (e.g., instantaneous correlation of A-train satellite observations) is unlikely to capture the true extent of smoke–cloud interaction in the southeast Atlantic.</p

Cloud processing and weeklong ageing affect biomass burning aerosol properties over the south-eastern Atlantic

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: Data from the CLARIFY aircraft campaign are available on the CEDA repository at http://catalogue.ceda.ac.uk/uuid/38ab7089781a4560b067dd6c20af3769 (last access: 2022-07-04). Data from ORACLES aircraft campaigns are available on the repository at https://espo.nasa.gov/oracles/archive/browse/oracles/id14 (last access: 2022-07-04). ERA5 reanalysis data (https://doi.org/10.24381/cds.bd0915c6) can be obtained from https://cds.climate.copernicus.eu. The SEVIRI cloud poduct are provided by NASA Langley, and are available in: https://satcorps.larc.nasa.gov/cgi-bin/site/showdoc?docid=22&lkdomain=Y&domain=ORACLES (last access: 2022-07-04). GPM precipitation data (https://doi.org/10.5067/GPM/IMERG/3B-HH/06) can be obtained from: https://disc.gsfc.nasa.gov/datasets/GPM_3IMERGHH_06/summary (last access: 2022-07-04). SEVIRI fire data in Supplements are from the geostationary satellite Meteosat-8, and can be obtained from: https://navigator.eumetsat.int/product/EO:EUM:DAT:MSG:FRP-SEVIRI (last access: 2022-07-04). MODIS wildfire data (https://doi.org/10.5067/FIRMS/MODIS/MCD14DL.NRT.0061) in supplements are from NASA FIRMS https://earthdata.nasa.gov/firms (last access: 2022-07-04).Southern Africa produces a third of global biomass burning emissions, which have a long atmospheric lifetime and influence regional radiation balance and climate. Here, we use airmass trajectories to link different aircraft observations to investigate the evolution of biomass-burning aerosols during their westward transport from Southern Africa over the south-eastern Atlantic, where a semi-permanent stratocumulus cloud deck is located. Our results show secondary organic aerosol formation during the initial 3 days of transport, followed by decreases in organic aerosol via photolysis before reaching equilibrium. Aerosol absorption wavelength dependency decreases with ageing, due to an increase in particle size and photochemical bleaching of brown carbon. Cloud processing, including aqueous-phase reaction and scavenging, contributes to the oxidation of organic aerosols, while it strongly reduces large diameter particles and single-scattering albedo of biomass burning aerosols. Together, these processes resulted in a marine boundary layer with fewer yet more oxidized and absorbing aerosols.Natural Environment Research Council (NERC)Earth Venture Suborbital-2 (EVS-2) progra

Biomass burning and marine aerosol processing over the southeast Atlantic Ocean: a TEM single-particle analysis

This study characterizes single-particle aerosol composition from filters collected during the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) and CLoud–Aerosol–Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) campaigns. In particular the study describes aged biomass burning aerosol (BBA), its interaction with the marine boundary layer and the influence of biomass burning (BB) air on marine aerosol. The study finds evidence of BBA influenced by marine boundary layer processing as well as sea salt influenced by BB air. Secondary chloride aerosols were observed in clean marine air as well as in BB-influenced air in the free troposphere. Higher-volatility organic aerosol appears to be associated with increased age of biomass burning plumes, and photolysis or oxidation may be a mechanism for the apparent increased volatility. Aqueous processing and interaction with the marine boundary layer air may be a mechanism for the presence of sodium on many aged potassium salts. By number, biomass burning potassium salts and modified sea salts are the most observed particles on filter samples. The most commonly observed BC coatings are inorganic salts. These results suggest that atmospheric processes such as photolysis, oxidation and cloud processing are key drivers in the elemental composition and morphology of aged BBA. Fresh BBA inorganic salt content, as it has an important role in the particles' ability to uptake water, may be a key driver in how aqueous processing and atmospheric aging proceed.</p

Use of lidar aerosol extinction and backscatter coefficients to estimate cloud condensation nuclei (CCN) concentrations in the southeast Atlantic

Accurately capturing cloud condensation nuclei (CCN) concentrations is key to understanding the aerosol–cloud interactions that continue to feature the highest uncertainty amongst numerous climate forcings. In situ CCN observations are sparse, and most non-polarimetric passive remote sensing techniques are limited to providing column-effective CCN proxies such as total aerosol optical depth (AOD). Lidar measurements, on the other hand, resolve profiles of aerosol extinction and/or backscatter coefficients that are better suited for constraining vertically resolved aerosol optical and microphysical properties. Here we present relationships between aerosol backscatter and extinction coefficients measured by the airborne High Spectral Resolution Lidar 2 (HSRL-2) and in situ measurements of CCN concentrations. The data were obtained during three deployments in the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) project, which took place over the southeast Atlantic (SEA) during September 2016, August 2017, and September–October 2018. Our analysis of spatiotemporally collocated in situ CCN concentrations and HSRL-2 measurements indicates strong linear relationships between both data sets. The correlation is strongest for supersaturations (S) greater than 0.25 % and dry ambient conditions above the stratocumulus deck, where relative humidity (RH) is less than 50 %. We find CCN–HSRL-2 Pearson correlation coefficients between 0.95–0.97 for different parts of the seasonal burning cycle that suggest fundamental similarities in biomass burning aerosol (BBA) microphysical properties. We find that ORACLES campaign-average values of in situ CCN and in situ extinction coefficients are qualitatively similar to those from other regions and aerosol types, demonstrating overall representativeness of our data set. We compute CCN–backscatter and CCN–extinction regressions that can be used to resolve vertical CCN concentrations across entire above-cloud lidar curtains. These lidar-derived CCN concentrations can be used to evaluate model performance, which we illustrate using an example CCN concentration curtain from the Weather Research and Forecasting Model coupled with physics packages from the Community Atmosphere Model version 5 (WRF-CAM5). These results demonstrate the utility of deriving vertically resolved CCN concentrations from lidar observations to expand the spatiotemporal coverage of limited or unavailable in situ observations.</p

Daytime aerosol optical depth above low-level clouds is similar to that in adjacent clear skies at the same heights: airborne observation above the southeast Atlantic

To help satellite retrieval of aerosols and studies of their radiative effects, we demonstrate that daytime aerosol optical depth over low-level clouds is similar to that in neighboring clear skies at the same heights. Based on recent airborne lidar and sun photometer observations above the southeast Atlantic, the mean aerosol optical depth (AOD) difference at 532&thinsp;nm is between 0 and &minus;0.01, when comparing the cloudy and clear sides, each up to 20&thinsp;km wide, of cloud edges. The difference is not statistically significant according to a paired t&nbsp;test. Systematic differences in the wavelength dependence of AOD and in situ single scattering albedo are also minuscule. These results hold regardless of the vertical distance between cloud top and aerosol layer bottom. AOD aggregated over &sim;2∘ grid boxes for each of September 2016, August 2017 and October 2018 also shows little correlation with the presence of low-level clouds. We posit that a satellite retrieval artifact is entirely responsible for a previous finding of generally smaller AOD over clouds (Chung et al., 2016), at least for the region and time of our study. Our results also suggest that the same values can be assumed for the intensive properties of free-tropospheric biomass-burning aerosol regardless of whether clouds are present below. &nbsp;</p

Intercomparison of airborne and surface-based measurements during the CLARIFY, ORACLES and LASIC field experiments

This is the final version. Available on open access from the European Geosciences Union via the DOI in this recordCode availability: Processing code for the FAAM core measurements suite is available from GitHub (Sproson et al., 2020).Data availability Airborne data for the CLARIFY campaign are available from the Centre for Environmental Data Analysis (Facility for Airborne Atmospheric Measurements et al., 2017) and for the ORACLES campaign from NASA Earth Science Project Office (ORACLES Science Team, 2020). The LASIC ground-based data sets are publicly available from the Atmospheric Radiation Measurement Climate Research Facility (Zuidema et al., 2017) with specialist data sets available for the following: SP2 – https://iop.archive.arm.gov/arm-iop/2016/ (last access: 25 October 2022, Sedlacek, 2017), CO – https://doi.org/10.5439/1046183 (Springston, 2018b), CAPS PMSSA – https://adc.arm.gov/discovery/#/results/s::caps-ssa (Onasch et al., 2015), ACSM – https://doi.org/10.5439/1763029 (Zawadowicz and Howie, 2021).Data are presented from intercomparisons between two research aircraft, the FAAM BAe-146 and the NASA Lockheed P3, and between the BAe-146 and the surface-based DOE (Department of Energy) ARM (Atmospheric Radiation Measurement) Mobile Facility at Ascension Island (8∘ S, 14.5∘ W; a remote island in the mid-Atlantic). These took place from 17 August to 5 September 2017, during the African biomass burning (BB) season. The primary motivation was to give confidence in the use of data from multiple platforms with which to evaluate numerical climate models. The three platforms were involved in the CLouds–Aerosol–Radiation Interaction and Forcing for Year 2017 (CLARIFY-2017), ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES), and Layered Atlantic Smoke and Interactions with Clouds (LASIC) field experiments. Comparisons from flight segments on 6 d where the BAe-146 flew alongside the ARM facility on Ascension Island are presented, along with comparisons from the wing-tip-to-wing-tip flight of the P3 and BAe-146 on 18 August 2017. The intercomparison flight sampled a relatively clean atmosphere overlying a moderately polluted boundary layer, while the six fly-bys of the ARM site sampled both clean and polluted conditions 2–4 km upwind. We compare and validate characterisations of aerosol physical, chemical and optical properties as well as atmospheric radiation and cloud microphysics between platforms. We assess the performance of measurement instrumentation in the field, under conditions where sampling conditions are not as tightly controlled as in laboratory measurements where calibrations are performed. Solar radiation measurements compared well enough to permit radiative closure studies. Optical absorption coefficient measurements from all three platforms were within uncertainty limits, although absolute magnitudes were too low (<10 Mm−1) to fully support a comparison of the absorption Ångström exponents. Aerosol optical absorption measurements from airborne platforms were more comparable than aircraft-to-ground observations. Scattering coefficient observations compared adequately between airborne platforms, but agreement with ground-based measurements was worse, potentially caused by small differences in sampling conditions or actual aerosol population differences over land. Chemical composition measurements followed a similar pattern, with better comparisons between the airborne platforms. Thermodynamics, aerosol and cloud microphysical properties generally agreed given uncertainties.Natural Environment Research Council (NERC)NERC/Met Office Industrial Case studentshipResearch Council of NorwayUS Department of Energy, Office of ScienceNASAUS Department of Energy Atmospheric Systems Research (ASR) programm

An overview of the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) project: aerosol–cloud–radiation interactions in the southeast Atlantic basin

This is the final version. Available on open access from the European Geosciences Union via the DOI in this recordData availability: All ORACLES data are accessible via the digital object identifiers (DOIs) provided under ORACLES Science Team (2020a–d) references: https://doi.org/10.5067/Suborbital/ORACLES/P3/2018_V2 (ORACLES Science Team, 2020a), https://doi.org/10.5067/Suborbital/ORACLES/P3/2017_V2 (ORACLES Science Team, 2020b), https://doi.org/10.5067/Suborbital/ORACLES/P3/2016_V2 (ORACLES Science Team, 2020c), and https://doi.org/10.5067/Suborbital/ORACLES/ER2/2016_V2 (ORACLES Science Team, 2020d). The only exceptions are noted as footnotes to Table B2.Southern Africa produces almost a third of the Earth's biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three intensive observation periods designed to study key atmospheric processes that determine the climate impacts of these aerosols. During the Southern Hemisphere winter and spring (June–October), aerosol particles reaching 3–5 km in altitude are transported westward over the southeast Atlantic, where they interact with one of the largest subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, as well as due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017, and October 2018 (totaling ∼350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ∼100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science themes centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects, (b) effects of aerosol absorption on atmospheric circulation and clouds, and (c) aerosol–cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the dataset it produced.NAS

Lithostratigraphy of tills and proglacial deposits in the Szczecin vicinity, northwestern Poland

W regionie szczecińskim występuje 9 poziomów różnowiekowych glin lodowcowych, które zdefiniowano na podstawie ich składu petrograficznego oraz pozycji w sukcesji litostratygraficznej. Poziomy te reprezentują najstarsze zlodowacenie (jedna glina), zlodowacenia południowopolskie (2 gliny), zlodowacenia środkowopolskie (3 gliny) oraz zlodowacenia północnopolskie (2 gliny o regionalnym zasięgu i jedna glina występująca lokalnie, w strefie moren czołowych fazy poznańskiej). Dla wszystkich poziomów glin dokonano formalizacji litostratygraficznej. Niektóre poziomy glin regionu szczecińskiego posiadają cechy, które pozwalają korelować je z glinami o podobnych cechach z zachodniej i centralnej Polski. Wiek innych poziomów glin określono na podstawie ich pozycji w stosunku do horyzontów przewodnich. Kierunki transportu glacjalnego dla wczesnych stadiałów zlodowaceń są zazwyczaj z NW na SE, podczas gdy w młodszych stadiałach zmieniają się na NE-SW, a w najmłodszych na ENE-WSW. W regionie szczecińskim nie udokumentowano istnienia żadnych osadów interglacjalnych lub interstadialnych, natomiast występują powszechnie osady proglacjalne, w tym bardzo miąższe serie zastoiskowe. Te ostatnie udokumentowano prawie dla wszystkich awansów lądolodów i reprezentują one głównie zbiorniki z faz transgresywnych zlodowaceń. W badanym regionie wydzielono dwie główne kopalne powierzchnie erozyjno-denudacyjne, jedną z okresu międzylodowcowego pomiędzy zlodowaceniami południowopolskimi a środkowopolskimi, a drugą z okresu interglacjału eemskiego i wczesnego Vistulianu. Różniły się one intensywnością erozji i charakterem dominujących procesów: w pierwszym okresie przeważała denudacja i powierzchniowe obniżanie terenu, a w drugim prawdopodobnie bardziej intensywna była głęboka erozja rzeczna. Starsze i młodsze serie glacjalne zawierają domieszki materiału wczesnokenozoicznego, podczas gdy osady ze zlodowaceń środkowopolskich takich domieszek nie mają. Świadczy to o występowaniu licznych wychodni podłoża neogeńskiego, a pośrednio też o intensywnej erozji przed i w czasie zlodowaceń najstarszych, południowopolskich i północnopolskich. Natomiast w czasie zlodowaceń środkowopolskich lądolody nasuwały się na obszar z ciągłą pokrywą starszych osadów glacjalnych.In the vicinity of Szczecin, NW Poland, 9 till horizons occur which have been defined by their petrographic composition and position in lithostratigraphic succession. The tills include to the "oldest glaciation", two tills to Elsterian, three tills to Saalian and three tills to Weichselian (two of them with regional extent, and one local, connected with the marginal zone of the Pomerania Phase). This stratigraphic subdivision was formalized. Some tills of the Szczecin region indicate features which are correlative with till horizons in western and central Poland. The age of other tills has been established in relation to these index horizons. Glacial palaeotransport was usually from NW to SE during the first stadials of each glaciation, then changed from NE to SW in the middle, and finally to ENE-WSW in the final stadials. There are no interglacial or interstadial deposits near Szczecin, but proglacial sediments have a widespread occurrence, particularly glaciolacustrine series. The latter are quite thick and occur in almost all glacial horizons. Glaciolacustrine deposits were formed mainly during the ice sheet advances. Two regional, buried palaeosurfaces have been documented in the studied area. They were formed during the Mazovian (Holstein) Interglacial (Elsterian/Saalian ice free period) and during the Eemian and early Vistulian. Each of them was formed by different processes, the first one by regional denudation and slow lowering of the surface, and the second one probably also by more intensive and deep fluvial erosion. The sediments from the oldest glaciations (San 1 and San 2) and Vistulian contain admixtures of early Cenozoic material, whereas Middle Polish (Saalian) deposits do not. From this it follows that during the first there were many outcrops of older sediments, exposed due to intensive erosion, whereas the Middle Polish (Saalisan) ice sheets advanced to the area covered by continuous cover of older glacial deposits