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- ItemThe realization of autonomous, aircraft-based, real-time aerosol mass spectrometry in the upper troposphere and lower stratosphere(Katlenburg-Lindau : Copernicus, 2022) Dragoneas, Antonis; Molleker, Sergej; Appel, Oliver; Hünig, Andreas; Böttger, Thomas; Hermann, Markus; Drewnick, Frank; Schneider, Johannes; Weigel, Ralf; Borrmann, StephanWe report on the developments that enabled the field deployment of a fully automated aerosol mass spectrometer, especially designed for high-altitude measurements on unpressurized aircraft. The merits of the two main categories of real-time aerosol mass spectrometry, i.e. (a) single-particle laser desorption and ionization and (b) continuous thermal desorption and electron impact ionization of aerosols, have been integrated into one compact apparatus with the aim to perform in situ real-time analysis of aerosol chemical composition. The demonstrated instrument, named the ERICA (European Research Council Instrument for Chemical composition of Aerosols), operated successfully aboard the high-altitude research aircraft M-55 Geophysica at altitudes up to 20 km while being exposed to ambient conditions of very low atmospheric pressure and temperature. A primary goal of those field deployments was the in situ study of the Asian tropopause aerosol layer (ATAL). During 11 research flights, the instrument operated for more than 49 h and collected chemical composition information of more than 150 000 single particles combined with quantitative chemical composition analysis of aerosol particle ensembles. This paper presents in detail the technical characteristics of the main constituent parts of the instrument, as well as the design considerations for its integration into the aircraft and its autonomous operation in the upper troposphere and lower stratosphere (UTLS). Additionally, system performance data from the first field deployments of the instrument are presented and discussed, together with exemplary mass spectrometry data collected during those flights.
- ItemTropospheric and stratospheric wildfire smoke profiling with lidar: mass, surface area, CCN, and INP retrieval(Katlenburg-Lindau : European Geosciences Union, 2021) Ansmann, Albert; Ohneiser, Kevin; Mamouri, Rodanthi-Elisavet; Knopf, Daniel A.; Veselovskii, Igor; Baars, Holger; Engelmann, Ronny; Foth, Andreas; Jimenez, Cristofer; Seifert, Patric; Barja, BorisWe present retrievals of tropospheric and stratospheric height profiles of particle mass, volume, surface area, and number concentrations in the case of wildfire smoke layers as well as estimates of smoke-related cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations from backscatter lidar measurements on the ground and in space. Conversion factors used to convert the optical measurements into microphysical properties play a central role in the data analysis, in addition to estimates of the smoke extinction-to-backscatter ratios required to obtain smoke extinction coefficients. The set of needed conversion parameters for wildfire smoke is derived from AERONET observations of major smoke events, e.g., in western Canada in August 2017, California in September 2020, and southeastern Australia in January-February 2020 as well as from AERONET long-term observations of smoke in the Amazon region, southern Africa, and Southeast Asia. The new smoke analysis scheme is applied to CALIPSO observations of tropospheric smoke plumes over the United States in September 2020 and to ground-based lidar observation in Punta Arenas, in southern Chile, in aged Australian smoke layers in the stratosphere in January 2020. These case studies show the potential of spaceborne and ground-based lidars to document large-scale and long-lasting wildfire smoke events in detail and thus to provide valuable information for climate, cloud, and air chemistry modeling efforts performed to investigate the role of wildfire smoke in the atmospheric system. © 2021 Albert Ansmann et al.
- ItemCharacterization of organic aerosol across the global remote troposphere: A comparison of ATom measurements and global chemistry models(Katlenburg-Lindau : EGU, 2020) Hodzic, Alma; Campuzano-Jost, Pedro; Bian, Huisheng; Chin, Mian; Colarco, Peter R.; Day, Douglas A.; Froyd, Karl D.; Heinold, Bernd; Katich, Joseph M.; Jo, Duseong S.; Kodros, John K.; Nault, Benjamin A.; Pierce, Jeffrey R.; Ray, Eric; Schacht, Jacob; Schill, Gregory P.; Schroder, Jason C.; Schwarz, Joshua P.; Sueper, Donna T.; Tegen, Ina; Tilmes, Simone; Tsigaridis, Kostas; Yu, Pengfei; Jimenez, Jose L.The spatial distribution and properties of submicron organic aerosol (OA) are among the key sources of uncertainty in our understanding of aerosol effects on climate. Uncertainties are particularly large over remote regions of the free troposphere and Southern Ocean, where very few data have been available and where OA predictions from AeroCom Phase II global models span 2 to 3 orders of magnitude, greatly exceeding the model spread over source regions. The (nearly) pole-to-pole vertical distribution of nonrefractory aerosols was measured with an aerosol mass spectrometer onboard the NASA DC-8 aircraft as part of the Atmospheric Tomography (ATom) mission during the Northern Hemisphere summer (August 2016) and winter (February 2017). This study presents the first extensive characterization of OA mass concentrations and their level of oxidation in the remote atmosphere. OA and sulfate are the major contributors by mass to submicron aerosols in the remote troposphere, together with sea salt in the marine boundary layer. Sulfate was dominant in the lower stratosphere. OA concentrations have a strong seasonal and zonal variability, with the highest levels measured in the lower troposphere in the summer and over the regions influenced by biomass burning from Africa (up to 10 μgsm-3). Lower concentrations (~ 0:1 0.3 μgsm-3) are observed in the northern middle and high latitudes and very low concentrations (< 0:1 μgsm-3) in the southern middle and high latitudes. The ATom dataset is used to evaluate predictions of eight current global chemistry models that implement a variety of commonly used representations of OA sources and chemistry, as well as of the AeroCom-II ensemble. The current model ensemble captures the average vertical and spatial distribution of measured OA concentrations, and the spread of the individual models remains within a factor of 5. These results are significantly improved over the AeroCom-II model ensemble, which shows large overestimations over these regions. However, some of the improved agreement with observations occurs for the wrong reasons, as models have the tendency to greatly overestimate the primary OA fraction and underestimate the sec-ondary fraction. Measured OA in the remote free troposphere is highly oxygenated, with organic aerosol to organic carbon (OA= OC) ratios of ~ 2.2 2.8, and is 30 % 60% more oxygenated than in current models, which can lead to significant errors in OA concentrations. The model measurement comparisons presented here support the concept of a more dynamic OA system as proposed by Hodzic et al. (2016), with enhanced removal of primary OA and a stronger production of secondary OA in global models needed to provide better agreement with observations. © 2020 IEEE Computer Society. All rights reserved.
- ItemValidation of Aeolus wind products above the Atlantic Ocean(Katlenburg-Lindau : Copernicus, 2020) Baars, Holger; Herzog, Alina; Heese, Birgit; Ohneiser, Kevin; Hanbuch, Karsten; Hofer, Julian; Yin, Zhenping; Engelmann, Ronny; Wandinger, UllaIn August 2018, the first Doppler wind lidar in space called Atmospheric Laser Doppler Instrument (ALADIN) was launched on board the satellite Aeolus by the European Space Agency (ESA). Aeolus measures profiles of one horizontal wind component (i.e., mainly the west-east direction) in the troposphere and lower stratosphere on a global basis. Furthermore, profiles of aerosol and cloud properties can be retrieved via the high spectral resolution lidar (HSRL) technique. The Aeolus mission is supposed to improve the quality of weather forecasts and the understanding of atmospheric processes. We used the opportunity to perform a unique validation of the wind products of Aeolus by utilizing the RV Polarstern cruise PS116 from Bremerhaven to Cape Town in November/December 2018. Due to concerted course modifications, six direct intersections with the Aeolus ground track could be achieved in the Atlantic Ocean west of the African continent. For the validation of the Aeolus wind products, we launched additional radiosondes and used the EARLINET/ACTRIS lidar Polly XT for atmospheric scene analysis. The six analyzed cases prove that Aeolus is able to measure horizontal wind speeds in the nearly west-east direction. Good agreements with the radiosonde observations could be achieved for both Aeolus wind products-the winds observed in clean atmospheric regions called Rayleigh winds and the winds obtained in cloud layers called Mie winds (according to the responsible scattering regime). Systematic and statistical errors of the Rayleigh winds were less than 1.5 and 3.3ms-1, respectively, when compared to radiosonde values averaged to the vertical resolution of Aeolus. For the Mie winds, a systematic and random error of about 1ms-1 was obtained from the six comparisons in different climate zones. However, it is also shown that the coarse vertical resolution of 2km in the upper troposphere, which was set in this early mission phase 2 months after launch, led to an underestimation of the maximum wind speed in the jet stream regions. In summary, promising first results of the first wind lidar space mission are shown and prove the concept of Aeolus for global wind observations. © 2020 Author(s).
- ItemCharacterization of aerosol particles at Cabo Verde close to sea level and at the cloud level – Part 2: Ice-nucleating particles in air, cloud and seawater(Katlenburg-Lindau : EGU, 2020) Gong, Xianda; Wex, Heike; van Pinxteren, Manuela; Triesch, Nadja; Fomba, Khanneh Wadinga; Lubitz, Jasmin; Stolle, Christian; Robinson, Tiera-Brandy; Müller, Thomas; Herrmann, Hartmut; Stratmann, FrankIce-nucleating particles (INPs) in the troposphere can form ice in clouds via heterogeneous ice nucleation. Yet, atmospheric number concentrations of INPs (NINP) are not well characterized, and, although there is some understanding of their sources, it is still unclear to what extend different sources contribute or if all sources are known. In this work, we examined properties of INPs at Cabo Verde (a.k.a. Cape Verde) from different environmental compartments: the oceanic sea surface microlayer (SML), underlying water (ULW), cloud water and the atmosphere close to both sea level and cloud level. Both enrichment and depletion of NINP in SML compared to ULW were observed. The enrichment factor (EF) varied from roughly 0.4 to 11, and there was no clear trend in EF with ice-nucleation temperature. NINP values in PM10 sampled at Cape Verde Atmospheric Observatory (CVAO) at any particular ice-nucleation temperature spanned around 1 order of magnitude below −15 ∘C, and about 2 orders of magnitude at warmer temperatures (>−12 ∘C). Among the 17 PM10 samples at CVAO, three PM10 filters showed elevated NINP at warm temperatures, e.g., above 0.01 L−1 at −10 ∘C. After heating samples at 95 ∘C for 1 h, the elevated NINP at the warm temperatures disappeared, indicating that these highly ice active INPs were most likely biological particles. INP number concentrations in PM1 were generally lower than those in PM10 at CVAO. About 83±22 %, 67±18 % and 77±14 % (median±standard deviation) of INPs had a diameter >1 µm at ice-nucleation temperatures of −12, −15 and −18 ∘C, respectively. PM1 at CVAO did not show such elevated NINP at warm temperatures. Consequently, the difference in NINP between PM1 and PM10 at CVAO suggests that biological ice-active particles were present in the supermicron size range. NINP in PM10 at CVAO was found to be similar to that on Monte Verde (MV, at 744 m a.s.l.) during noncloud events. During cloud events, most INPs on MV were activated to cloud droplets. When highly ice active particles were present in PM10 filters at CVAO, they were not observed in PM10 filters on MV but in cloud water samples instead. This is direct evidence that these INPs, which are likely biological, are activated to cloud droplets during cloud events. For the observed air masses, atmospheric NINP values in air fit well to the concentrations observed in cloud water. When comparing concentrations of both sea salt and INPs in both seawater and PM10 filters, it can be concluded that sea spray aerosol (SSA) only contributed a minor fraction to the atmospheric NINP. This latter conclusion still holds when accounting for an enrichment of organic carbon in supermicron particles during sea spray generation as reported in literature.
- ItemHow the extreme 2019-2020 Australian wildfires affected global circulation and adjustments(Katlenburg-Lindau : EGU, 2023) Senf, Fabian; Heinold, Bernd; Kubin, Anne; Müller, Jason; Schrödner, Roland; Tegen, InaWildfires are a significant source of absorbing aerosols in the atmosphere. Extreme fires in particular, such as those during the 2019-2020 Australian wildfire season (Black Summer fires), can have considerable large-scale effects. In this context, the climate impact of extreme wildfires unfolds not only because of the emitted carbon dioxide but also due to smoke aerosol released up to an altitude of 17ĝ€¯km. The overall aerosol effects depend on a variety of factors, such as the amount emitted, the injection height, and the composition of the burned material, and is therefore subject to considerable uncertainty. In the present study, we address the global impact caused by the exceptionally strong and high-reaching smoke emissions from the Australian wildfires using simulations with a global aerosol-climate model. We show that the absorption of solar radiation by the black carbon contained in the emitted smoke led to a shortwave radiative forcing of more than +5ĝ€¯Wm-2 in the southern mid-latitudes of the lower stratosphere. Subsequent adjustment processes in the stratosphere slowed down the diabatically driven meridional circulation, thus redistributing the heating perturbation on a global scale. As a result of these stratospheric adjustments, a positive temperature perturbation developed in both hemispheres, leading to additional longwave radiation emitted back to space. According to the model results, this adjustment occurred in the stratosphere within the first 2 months after the event. At the top of the atmosphere (TOA), the net effective radiative forcing (ERF) averaged over the Southern Hemisphere was initially dominated by the instantaneous positive radiative forcing of about +0.5ĝ€¯Wm-2, for which the positive sign resulted mainly from the presence of clouds above the Southern Ocean. The longwave adjustments led to a compensation of the initially net positive TOA ERF, which is seen in the Southern Hemisphere, the tropics, and the northern mid-latitudes. The simulated changes in the lower stratosphere also affected the upper troposphere through a thermodynamic downward coupling. Subsequently, increased temperatures were also obtained in the upper troposphere, causing a global decrease in relative humidity, cirrus amount, and the ice water path of about 0.2ĝ€¯%. As a result, surface precipitation also decreased by a similar amount, which was accompanied by a weakening of the tropospheric circulation due to the given energetic constraints. In general, it appears that the radiative effects of smoke from single extreme wildfire events can lead to global impacts that affect the interplay of tropospheric and stratospheric budgets in complex ways. This emphasizes that future changes in extreme wildfires need to be included in projections of aerosol radiative forcing.
- ItemRole of the dew water on the ground surface in HONO distribution: A case measurement in Melpitz(Katlenburg-Lindau : EGU, 2020) Ren, Yangang; Stieger, Bastian; Spindler, Gerald; Grosselin, Benoit; Mellouki, Abdelwahid; Tuch, Thomas; Wiedensohler, Alfred; Herrmann, HartmutTo characterize the role of dew water for the ground surface HONO distribution, nitrous acid (HONO) measurements with a Monitor for AeRosols and Gases in ambient Air (MARGA) and a LOng Path Absorption Photometer (LOPAP) instrument were performed at the Leibniz Institute for Tropospheric Research (TROPOS) research site in Melpitz, Germany, from 19 to 29 April 2018. The dew water was also collected and analyzed from 8 to 14 May 2019 using a glass sampler. The high time resolution of HONO measurements showed characteristic diurnal variations that revealed that (i) vehicle emissions are a minor source of HONO at Melpitz station; (ii) the heterogeneous conversion of NO2 to HONO on the ground surface dominates HONO production at night; (iii) there is significant nighttime loss of HONO with a sink strength of 0.16±0.12ppbv h-1; and (iv) dew water with mean NO-2 of 7.91±2.14 μgm-2 could serve as a temporary HONO source in the morning when the dew droplets evaporate. The nocturnal observations of HONO and NO2 allowed the direct evaluation of the ground uptake coefficients for these species at night: γNO2→HONO = 2.4±10-7 to 3.5±10-6, γHONO;ground = 1.7×10-5 to 2.8×10-4. A chemical model demonstrated that HONO deposition to the ground surface at night was 90 %-100% of the calculated unknown HONO source in the morning. These results suggest that dew water on the ground surface was controlling the temporal HONO distribution rather than straightforward NO2-HONO conversion. This can strongly enhance the OH reactivity throughout the morning time or in other planted areas that provide a large amount of ground surface based on the OH production rate calculation. © 2020 Copernicus GmbH. All rights reserved.
- ItemThe role of atmospheric rivers in the distribution of heavy precipitation events over North America(Munich : EGU, 2023) Vallejo-Bernal, Sara M.; Wolf, Frederik; Boers, Niklas; Traxl, Dominik; Marwan, Norbert; Kurths, JürgenAtmospheric rivers (ARs) are filaments of extensive water vapor transport in the lower troposphere that play a crucial role in the distribution of freshwater but can also cause natural and economic damage by facilitating heavy precipitation. Here, we investigate the large-scale spatiotemporal synchronization patterns of heavy precipitation events (HPEs) over the western coast and the continental regions of North America (NA), during the period from 1979 to 2018. In particular, we use event synchronization and a complex network approach incorporating varying delays to examine the temporal evolution of spatial patterns of HPEs in the aftermath of land-falling ARs. For that, we employ the SIO-R1 catalog of ARs that landfall on the western coast of NA, ranked in terms of intensity and persistence on an AR-strength scale which varies from level AR1 to AR5, along with daily precipitation estimates from ERA5 with a 0.25'spatial resolution. Our analysis reveals a cascade of synchronized HPEs, triggered by ARs of level AR3 or higher. On the first 3d after an AR makes landfall, HPEs mostly occur and synchronize along the western coast of NA. In the subsequent days, moisture can be transported to central and eastern Canada and cause synchronized but delayed HPEs there. Furthermore, we confirm the robustness of our findings with an additional AR catalog based on a different AR detection method. Finally, analyzing the anomalies of integrated water vapor transport, geopotential height, upper-level meridional wind, and precipitation, we find atmospheric circulation patterns that are consistent with the spatiotemporal evolution of the synchronized HPEs. Revealing the role of ARs in the precipitation patterns over NA will lead to a better understanding of inland HPEs and the effects that changing climate dynamics will have on precipitation occurrence and consequent impacts in the context of a warming atmosphere.
- ItemIs the near-spherical shape the "new black" for smoke?(Katlenburg-Lindau : EGU, 2020) Gialitaki, Anna; Tsekeri, Alexandra; Amiridis, Vassilis; Ceolato, Romain; Paulien, Lucas; Kampouri, Anna; Gkikas, Antonis; Solomos, Stavros; Marinou, Eleni; Haarig, Moritz; Baars, Holger; Ansmann, Albert; Lapyonok, Tatyana; Lopatin, Anton; Dubovik, Oleg; Groß, Silke; Wirth, Martin; Tsichla, Maria; Tsikoudi, Ioanna; Balis, DimitrisWe examine the capability of near-sphericalshaped particles to reproduce the triple-wavelength particle linear depolarization ratio (PLDR) and lidar ratio (LR) values measured over Europe for stratospheric smoke originating from Canadian wildfires. The smoke layers were detected both in the troposphere and the stratosphere, though in the latter case the particles presented PLDR values of almost 18% at 532 nm as well as a strong spectral dependence from the UV to the near-IR wavelength. Although recent simulation studies of rather complicated smoke particle morphologies have shown that heavily coated smoke aggregates can produce large PLDR, herein we propose a much simpler model of compact near-spherical smoke particles. This assumption allows for the reproduction of the observed intensive optical properties of stratospheric smoke, as well as their spectral dependence. We further examine whether an extension of the current Aerosol Robotic Network (AERONET) scattering model to include the near-spherical shapes could be of benefit to the AERONET retrieval for stratospheric smoke cases associated with enhanced PLDR. Results of our study illustrate the fact that triple-wavelength PLDR and LR lidar measurements can provide us with additional insight when it comes to particle characterization. © 2020 Author(s).
- ItemNext-generation ice-nucleating particle sampling on board aircraft: characterization of the High-volume flow aERosol particle filter sAmpler (HERA)(Katlenburg-Lindau : Copernicus, 2023) Grawe, Sarah; Jentzsch, Conrad; Schaefer, Jonas; Wex, Heike; Mertes, Stephan; Stratmann, FrankAtmospheric ice-nucleating particle (INP) concentration data from the free troposphere are sparse but urgently needed to understand vertical transport processes of INPs and their influence on cloud formation and properties. Here, we introduce the new High-volume flow aERosol particle filter sAmpler (HERA) which was specially developed for installation on research aircraft and subsequent offline INP analysis. HERA is a modular system consisting of a sampling unit and a powerful pump unit, and it has several features which were integrated specifically for INP sampling. Firstly, the pump unit enables sampling at flow rates exceeding 100 L min-1, which is well above typical flow rates of aircraft INP sampling systems described in the literature (∼ 10 L min-1). Consequently, required sampling times to capture rare, high-temperature INPs (≥ -15 C) are reduced in comparison to other systems, and potential source regions of INPs can be confined more precisely. Secondly, the sampling unit is designed as a seven-way valve, enabling switching between six filter holders and a bypass with one filter being sampled at a time. In contrast to other aircraft INP sampling systems, the valve position is remote-controlled via software so that manual filter changes during flight are eliminated and the potential for sample contamination is decreased. This design is compatible with a high degree of automation, i.e., triggering filter changes depending on parameters like flight altitude, geographical location, temperature, or time. In addition to presenting the design and principle of operation of HERA, this paper describes laboratory characterization experiments with size-selected test substances, i.e., SNOMAX® and Arizona Test Dust. The particles were sampled on filters with HERA, varying either particle diameter (300 to 800 nm) or flow rate (10 to 100 L min-1) between experiments. The subsequent offline INP analysis showed good agreement with literature data and comparable sampling efficiencies for all investigated particle sizes and flow rates. Furthermore, the collection efficiency of atmospheric INPs in HERA was compared to a straightforward filter sampler and good agreement was found. Finally, results from the first campaign of HERA on the High Altitude and LOng range research aircraft (HALO) demonstrate the functionality of the new system in the context of aircraft application.