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NASA NTRSDate not supplied

Origins and Chemical Characteristics of a Plume Observed on 31 August 2019 by the Langley Mobile Ozone Lidar During the FIREX-AQ Field Campaign

During the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign, the Langley Mobile Ozone Lidar (LMOL) observed an aerosol plume over Hampton, VA between 0000–1200 UTC on August 31, 2019. This plume is of interest because it did not have any associated ozone (O3) and was only observable in LMOL’s new aerosol backscatter product derived while performing the aerosol correction procedure (Leietal.,2021). Here we investigate the origins and evolution of the chemical composition throughout the plume’s lifetime. This study also evaluates LMOL’s new aerosol capability, which allows us to better identify and understand smoke plumes.

Daniel B Phoenix↗
NASA NTRS2008

CALIPSO Observations of Volcanic Aerosol in the Stratosphere

In the stratosphere, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) has observed the presence of aerosol plumes associated with the eruptions several volcanoes including Montserrat (May 2006), Chaiten (May 2008), and Kasatochi (August 2008). While the dense ash plumes from these eruptions dissipate relatively quickly, CALIPSO continued to detect an enhanced aerosol layer from the Montserrat eruption from the initial observations in June 2006 well into 2008. Solar occultation missions were uniquely capable of monitoring stratospheric aerosol. However, since the end of long-lived instruments like the Stratospheric Aerosol and Gas Experiment (SAGE II), there has been no clear space-based successor instrument. A number of active instruments, some employing new techniques, are being evaluated as candidate sources of stratospheric aerosol data. Herein, we examine suitability of the CALIPSO 532-nm aerosol backscatter coefficient measurements.

Thomason, Larry W.↗
NASA NTRS2022

Space-based Passive Aerosol Remote Sensing from the Multi-angle Imaging SpectroRadiometer (MISR) Aboard NASA’s Terra Satellite

The Multi-angle Imaging SpectroRadiometer (MISR) instrument has been acquiring multi-angle imagery of the Earth aboard NASA’s Terra satellite since February 2000, providing an ongoing record of atmosphere and surface properties more than two decades long. MISR offers a combination of moderately high spatial resolution imagery at nine view angles in each of four visible/near-infrared spectral bands, global coverage about once per week, and carefully maintained onboard radiometric calibration. Unique algorithms retrieve aerosol column-amount and constraints on particle microphysical and optical properties, as well as the heights and motion vectors of aerosol plumes from sources such as wildfires, volcanic eruptions, and dust storms. Applications of MISR aerosol data to climate and air quality are discussed here along with a summary of some key scientific findings enabled by the instrument’s unique measurement approach.

aerosols↗
NASA NTRS2008

MISR Instrument Data Visualization

The MISR Interactive eXplorer (MINX) software functions both as a general-purpose tool to visualize Multiangle Imaging SpectroRadiometer (MISR) instrument data, and as a specialized tool to analyze properties of smoke, dust, and volcanic plumes. It includes high-level options to create map views of MISR orbit locations; scrollable, single-camera RGB (red-greenblue) images of MISR level 1B2 (L1B2) radiance data; and animations of the nine MISR camera images that provide a 3D perspective of the scenes that MISR has acquired. NASA Tech Briefs, September 2008 55 The plume height capability provides an accurate estimate of the injection height of plumes that is needed by air quality and climate modelers. MISR provides global high-quality stereo height information, and this program uses that information to perform detailed height retrievals of aerosol plumes. Users can interactively digitize smoke, dust, or volcanic plumes and automatically retrieve heights and winds, and can also archive MISR albedos and aerosol properties, as well as fire power and brightness temperatures associated with smoke plumes derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data. Some of the specialized options in MINX enable the user to do other tasks. Users can display plots of top-of-atmosphere bidirectional reflectance factors (BRFs) versus camera-angle for selected pixels. Images and animations can be saved to disk in various formats. Also, users can apply a geometric registration correction to warp camera images when the standard processing correction is inadequate. It is possible to difference the images of two MISR orbits that share a path (identical ground track), as well as to construct pseudo-color images by assigning different combinations of MISR channels (angle or spectral band) to the RGB display channels. This software is an interactive application written in IDL and compiled into an IDL Virtual Machine (VM) ".sav" file.

Nelson, David↗
NASA NTRS2013

New Stratospheric Dust Belt Due to the Chelyabinsk Bolide

The Ozone Mapping Profiler Suite (OMPS) Limb Profiler (LP) on the recently launched NASA/NOAA NPP/ Suomi satellite detected aerosol excess in the midstratosphere (25-45 km altitude) between 50degN and 70degN latitudes. OMPS/LP observations trace this aerosol plume to the meteor that struck near Chelyabinsk, Russia on 15 February 2013. This new dust layer, located above the Junge aerosol layer, has persisted over at least a 3 month period. Material collected on the ground following the bolide explosion showed that the meteor was mostly composed of olivine and pyroxenes. Simulations using Lagrangian and Eulerian atmospheric models trace the plume back to Chelyabinsk and confirm that the plume altitude was at altitudes between 25 and 45 km. The models also confirm the plume circumpolar longitudinal spreading observed by OMPS/LP, with propagation speeds up to 85 m/s.

Stratospheric aerosol↗
NASA NTRS2000

Ocean-color Satellites and the Phytoplankton-dust Connection

Results of a time series of satellite measurements of aerosol radiance made with two ocean-color sensors are presented. Data from the Coastal Zone Color Scanner (CZCS) were collected from 1978 to 1986. The follow-on sensor, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), has been transmitting data since September 1997. Both CZCS and SeaWiFS images successfully depicted regions of well-known, large-scale mineral aerosol plumes, the seasonality of which corresponds to that found by other satellite and land-based platforms. Aerosol radiance extractions were made for two subregions in the North Atlantic, both of which are recipients of regular mineral aerosol deposits originating from northwest Africa. In the almost eight-year time series obtained with CZCS, the annual cycle in both subregions follows a similar pattern each year and agrees well with results from the published literature. However, there is interannual variability and the observed fluctuations may be linked to climatic shifts associated with the North Atlantic Oscillation. The SeaWiFS annual cycle of aerosol radiance in both subregions closely followed that found in the CZCS climatology; SeaWiFS-measured aerosol optical thickness mirrors aerosol radiance to a high degree. The higher temporal resolution offered by the SeaWiFS data demonstrates the sporadic nature of dust events throughout the entire year and not only during the high dust season.

Stegmann, P. M.↗
NASA NTRSDate not supplied

Exploring the Elevated Water Vapor Signal Associated With the Free Tropospheric Biomass Burning Plume Over the Southeast Atlantic Ocean

In southern Africa, widespread agricultural fires produce substantial biomass burning (BB) emissions over the region. The seasonal smoke plumes associated with these emissions are then advected westward over the persistent stratocumulus cloud deck in the southeast Atlantic (SEA) Ocean, resulting in aerosol effects which vary with time and location. Much work has focused on the effects of these aerosol plumes, but previous studies have also described an elevated free tropospheric water vapor signal over the SEA. Water vapor influences climate in its own right, and it is especially important to consider atmospheric water vapor when quantifying aerosol–cloud interactions and aerosol radiative effects. Here we present airborne observations made during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign over the SEA Ocean. In observations collected from multiple independent instruments on the NASA P-3 aircraft (from near-surface to 6–7 km), we observe a strongly linear correlation between pollution indicators (carbon monoxide (CO) and aerosol loading) and atmospheric water vapor content, seen at all altitudes above the boundary layer. The focus of the current study is on the especially strong correlation observed during the ORACLES-2016 deployment (out of Walvis Bay, Namibia), but a similar relationship is also observed in the August 2017 and October 2018 ORACLES deployments. Using reanalyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), and specialized WRF-Chem simulations, we trace the plume–vapor relationship to an initial humid, smoky continental source region, where it mixes with clean, dry upper tropospheric air and then is subjected to conditions of strong westward advection, namely the southern African easterly jet (AEJ-S). Our analysis indicates that air masses likely left the continent with the same relationship between water vapor and carbon monoxide as was observed by aircraft. This linear relationship developed over the continent due to daytime convection within a deep continental boundary layer (up to ∼5–6 km) and mixing with higher-altitude air, which resulted in fairly consistent vertical gradients in CO and water vapor, decreasing with altitude and varying in time, but this water vapor does not originate as a product of the BB combustion itself. Due to a combination of conditions and mixing between the smoky, moist continental boundary layer and the dry and fairly clean upper-troposphere air above (∼6 km), the smoky, humid air is transported by strong zonal winds and then advected over the SEA (to the ORACLES flight region) following largely isentropic trajectories. Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) back trajectories support this interpretation. This work thus gives insights into the conditions and processes which cause water vapor to covary with plume strength. Better understanding of this relationship, including how it varies spatially and temporally, is important to accurately quantify direct, semi-direct, and indirect aerosol effects over this region.

Kristina Pistone↗
DOE OSTI2021

Exploring the elevated water vapor signal associated with the free tropospheric biomass burning plume over the southeast Atlantic Ocean

In southern Africa, widespread agricultural fires produce substantial biomass burning (BB) emissions over the region. The seasonal smoke plumes associated with these emissions are then advected westward over the persistent stratocumulus cloud deck in the southeast Atlantic (SEA) Ocean, resulting in aerosol effects which vary with time and location. Much work has focused on the effects of these aerosol plumes, but previous studies have also described an elevated free tropospheric water vapor signal over the SEA. Water vapor influences climate in its own right, and it is especially important to consider atmospheric water vapor when quantifying aerosol-cloud interactions and aerosol radiative effects. Here we present airborne observations made during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign over the SEA Ocean. In observations collected from multiple independent instruments on the NASA P-3 aircraft (from near-surface to 6-7 km), we observe a strongly linear correlation between pollution indicators (carbon monoxide (CO) and aerosol loading) and atmospheric water vapor content, seen at all altitudes above the boundary layer. The focus of the current study is on the especially strong correlation observed during the ORACLES-2016 deployment (out of Walvis Bay, Namibia), but a similar relationship is also observed in the August 2017 and October 2018 ORACLES deployments. Using reanalyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), and specialized WRF-Chem simulations, we trace the plume-vapor relationship to an initial humid, smoky continental source region, where it mixes with clean, dry upper tropospheric air and then is subjected to conditions of strong westward advection, namely the southern African easterly jet (AEJ-S). Our analysis indicates that air masses likely left the continent with the same relationship between water vapor and carbon monoxide as was observed by aircraft. This linear relationship developed over the continent due to daytime convection within a deep continental boundary layer (up to ~5-6 km) and mixing with higher-altitude air, which resulted in fairly consistent vertical gradients in CO and water vapor, decreasing with altitude and varying in time, but this water vapor does not originate as a product of the BB combustion itself. Due to a combination of conditions and mixing between the smoky, moist continental boundary layer and the dry and fairly clean upper-troposphere air above (~6 km), the smoky, humid air is transported by strong zonal winds and then advected over the SEA (to the ORACLES flight region) following largely isentropic trajectories. Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) back trajectories support this interpretation. This work thus gives insights into the conditions and processes which cause water vapor to covary with plume strength. Better understanding of this relationship, including how it varies spatially and temporally, is important to accurately quantify direct, semi-direct, and indirect aerosol effects over this region.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRSDate not supplied

Identifying Chemical and Optical Smoke Signatures in Suborbital Observations to Improve Model Projections

Biomass Burning (BB) fires are expected to occur more frequently in the future due to climate change, the build‐up of fuels due to fire suppression, and the expansion of the wildland‐urban interface [Schoennagel et al., 2017; Shivdenko & Schepaschenko, 2013; Stevens et al., 2014; Turner et al., 2019; Yue et al., 2015; Tilman et al., 2001]. Accurate knowledge of the abundance, distribution, and optical properties of absorbing aerosols such as BB smoke is essential to understanding regional and global aerosol radiative effects [Boucher et al., 2013]. It is recognized that differing fuel types (e.g., rice straw, ponderosa pine), combustion modes (i.e., flaming, smoldering or both) and temperature/ moisture content produce smoke with differing optical characteristics (e.g., aerosol light scattering and absorption) and component mixing ratios [e.g., BC, OC and inorganic species such as sulfate, potassium, chloride; Streets et al. 2003; Reid et al., 2005a, b; Janhäll et al., 2010; Sayer et al., 2014]. However, climate models often ascribe a fixed set of emission factors [i.e., amount of particulate for a given species released in the atmosphere per unit dry fuel burned; Darmenov and Dasilva, 2013] and optical properties [Hess et al., 1998] to all BB aerosol plumes, inherently limiting accurate representation of the global and regional heterogeneity of BB. The overarching goal of the proposed work is to improve the microphysical and optical representation of different types of Biomass Burning in Chemistry Transport Models. Our strategy is to capitalize on multiple airborne campaigns (e.g., ARCTAS, SEAC4RS, ORACLES, FIREX-AQ), which sampled different types of BB plumes at different aging stages. Models, when improved and combined with satellite, airborne, and ground observations will help address many aerosol science objectives from the NASA Decadal survey [National Academies of Sciences, Engineering, and Medicine. 2018].

Meloe Shenandoah F Kacenelenbogen↗
NASA NTRS2022

Machine-Learning Reveals Climate Forcing From Aerosols is Dominated by Increased Cloud Cover

Aerosol-cloud interactions have a potentially large impact on climate, but are poorly quantified and thus contribute a significant and long-standing uncertainty in climate projections. The impacts derived from climate models are poorly constrained by observations, because retrieving robust large-scale signals of aerosol-cloud interactions are frequently hampered by the considerable noise associated with meteorological co-variability. The Iceland-Holuhraun effusive eruption in 2014 resulted in a massive aerosol plume in an otherwise near-pristine environment and thus provided an ideal natural experiment to quantify cloud responses to aerosol perturbations. Here we disentangle significant signals from the noise of meteorological co-variability using a satellite-based machine-learning approach. Our analysis shows that aerosols from the eruption increased cloud cover by approximately 10%, and this appears to be the leading cause of climate forcing, rather than cloud brightening as previously thought. We find that volcanic aerosols do brighten clouds by reducing droplet size, but this has a significantly smaller radiative impact than changes in cloud fraction. These results add substantial observational constraints on the cooling impact of aerosols. Such constraints are critical for improving climate models, which still inadequately represent the complex macro-physical and micro-physical impacts of aerosol-cloud interactions.

Aerosols↗
NASA NTRSDate not supplied

Constraints on Wildfire Smoke Source Strength, Injection Height, and Particle Evolution

Aerosol sources are represented in climate and air quality models with an injection height and a source strength. We have applied a combination of Multi-angle Imaging SpectroRadiometer (MISR) and MODerate resolution Imaging Spectroradiometer (MODIS) observations to help constrain these two key model variables for wildfire smoke plumes. Injection height is obtained from MISR stereo imagery, which makes it possible to map plume elevation and estimate the associated motion vectors at plume altitude near-source, where contrast features in the plume can be identified in the multi-angle views. A current limitation of injection-height mapping is the relatively narrow MISR swath width (~380 km) and 10:30 AM equator crossing time on the day side of Earth. However, upcoming missions, as well as advanced imagers on geostationary platforms, promise to greatly expand the spatial and temporal range over which this technique can be applied. We estimate source strength by matching forward-simulated plume aerosol optical depth (AOD) from models with AOD snapshots retrieved from MODIS observations. This technique works best for large, isolated plumes common in boreal forest, and tends to fail where plume AOD is low and/or background AOD, distinct from the specific source of interest, is high. These two approaches for constraining aerosol modeling with satellite observations have been the subject of ongoing AeroCom/AeroSat studies by our group. A third effort applies the combination of MISR plume heights, wind vectors, and particle microphysical property constraints to infer smoke-plume particle evolution processes and timescales, including the emission and subsequent evolution of black and brown smoke. In this presentation, we will provide an update on the status of these efforts.

wildfire↗
DOE OSTI2020

Air quality impact of the Northern California Camp Fire of November 2018

The Northern California Camp Fire that took place in November 2018 was one of the most damaging environmental events in California history. Here, we analyze ground-based station observations of airborne particulate matter that has a diameter <2.5 µm (PM 2.5 ) across Northern California and conduct numerical simulations of the Camp Fire using the Weather Research and Forecasting model online coupled with chemistry (WRF-Chem). Simulations are evaluated against ground-based observations of PM 2.5 , black carbon, and meteorology, as well as satellite measurements, such as Tropospheric Monitoring Instrument (TROPOMI) aerosol layer height and aerosol index. The Camp Fire led to an increase in Bay Area PM 2.5 to over 50 µg m –3 for nearly 2 weeks, with localized peaks exceeding 300 µg m –3 . Using the Visible Infrared Imaging Radiometer Suite (VIIRS) high-resolution fire detection products, the simulations reproduce the magnitude and evolution of surface PM 2.5 concentrations, especially downwind of the wildfire. The overall spatial patterns of simulated aerosol plumes and their heights are comparable with the latest satellite products from TROPOMI. WRF-Chem sensitivity simulations are carried out to analyze uncertainties that arise from fire emissions, meteorological conditions, feedback of aerosol radiative effects on meteorology, and various physical parameterizations, including the planetary boundary layer model and the plume rise model. Downwind PM 2.5 concentrations are sensitive to both flaming and smoldering emissions over the fire, so the uncertainty in the satellite-derived fire emission products can directly affect the air pollution simulations downwind. Our analysis also shows the importance of land surface and boundary layer parameterization in the fire simulation, which can result in large variations in magnitude and trend of surface PM 2.5 . Inclusion of aerosol radiative feedback moderately improves PM 2.5 simulations, especially over the most polluted days. Results of this study can assist in the development of data assimilation systems as well as air quality forecasting of health exposures and economic impact studies.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1998

Aerosol analysis techniques and results from micro pulse lidar

The effect of clouds and aerosol on the atmospheric energy balance is a key global change problem. Full knowledge of aerosol distributions is difficult to obtain by passive sensing alone. Aerosol and cloud retrievals in several important areas can be significantly improved with active remote sensing by lidar. Micro Pulse Lidar (MPL) is an aerosol and cloud profilometer that provides a detailed picture of the vertical structure of boundary layer and elevated dust or smoke plume aerosols. MPL is a compact, fully eyesafe, ground-based, zenith pointing instrument capable of full-time, long-term unattended operation at 523 nm. In October of 1993, MPL began taking full-time measurements for the Atmospheric Radiation Measurement (ARM) program at its Southern Great Plains (SGP) site and has since expanded to ARM sites in the Tropical West Pacific (TWP) and the North Slope of Alaska (NSA). Other MPL's are moving out to some of the 60 world-wide Aerosol Robotic Network (AERONET) sites which are already equipped with automatic sun-sky scanning spectral radiometers providing total column optical depth measurements. Twelve additional MPL's have been purchased by NASA to add to the aerosol and cloud database of the EOS ground validation network. The original MPL vertical resolution was 300 meters but the newer versions have a vertical resolution of 30 meters. These expanding data sets offer a significant new resource for atmospheric radiation analysis. Under the direction of Jim Spinhirne, the MPL analysis team at NASA/GSFC has developed instrument correction and backscatter analysis techniques for ARM to detect cloud boundaries and analyze vertical aerosol structures. A summary of MPL applications is found in Hlavka (1997). With the aid of independent total column optical depth instruments such as the Multifilter Rotating Shadowband Radiometer (MFRSR) at the ARM sites or sun photometers at the AERONET sites, the MPL data can be calibrated, and time-resolved vertical profiles of aerosol optical depth as well as aerosol extinction can be calculated. The techniques used to calibrate the lidar, calculate the aerosol extinction-to-backscatter ratio, and produce profiles of aerosol extinction and aerosol optical depths, will be described. Results using these techniques will be presented for case studies at the ARM site in the Tropical West Pacific and later in the Southern Great Plains.

Hlavka, Dennis L.↗
NASA NTRS1984

Development of a global model for atmospheric backscatter at CO2 wavelengths

The effect of aerosol microphysical processes on the backscatter from an aerosol plume undergoing long-range atmospheric transport was studied. A numerical model which examines the effects of coagulation and sedimentation on an aerosol size distribution is under development and the initial results for a single homogeneous layer were obtained. Use was made of the SAGE/SAM II data set to study the global variation of aerosol concentration and, hence, to predict the variation of Beta sub CO2. Computer programs were written to determine the mean, median, and the probability distribution of the measured aerosol extinction as a function of altitude, latitude and geographical conditions. The first data sets analyzed in this way are under study. Data was used to study aerosol behavior over the U.S.A. and the Pacific Ocean.

Kent, G. S.↗
NASA NTRS1993

CO2 lidar backscatter experiment

The Aerosol/Lidar Science Group of the Remote Sensing Branch engages in experimental and theoretical studies of atmospheric aerosol scattering and atmospheric dynamics, emphasizing Doppler lidar as a primary tool. Activities include field and laboratory measurement and analysis efforts by in-house personnel, coordinated with similar efforts by university and government institutional researchers. The primary focus of activities related to understanding aerosol scattering is the GLObal Backscatter Experiment (GLOBE) program. GLOBE was initiated by NASA in 1986 to support the engineering design, performance simulation, and science planning for the prospective NASA Laser Atmospheric Wind Sounder (LAWS). The most important GLOBE scientific result has been identified of a background aerosol mode with a surprisingly uniform backscatter mixing ratio (backscatter normalized by air density) throughout a deep tropospheric layer. The backscatter magnitude of the background mode evident from the MSFC CW lidar measurements is remarkably similar to that evident from ground-based backscatter profile climatologies obtained by JPL in Pasadena CA, NOAA/WPL in Boulder CO, and by the Royal Signals and Radar Establishment in the United Kingdom. Similar values for the background mode have been inferred from the conversion of in situ aerosol microphysical measurements to backscatter using Mie theory. Little seasonal or hemispheric variation is evident in the survey mission data, as opposed to large variation for clouds, aerosol plums, and the marine boundary layer. Additional features include: localized aerosol residues from dissipated clouds, occasional regions having mass concentrations of nanograms per cubic meter and very low backscatter, and aerosol plumes extending thousands of kilometers and several kilometers deep. Preliminary comparison with meteorological observations thus far indicate correlation between backscatter and water vapor under high humidity conditions. Limited intercomparisons with the Stratospheric Aerosol and Gas Experiment (SAGE) limb extinction sounder shows differences in the troposphere, however, it should be noted that in general SAGE measurements have not yet been validated in the troposphere.

Jarzembski, Maurice A.↗
NASA NTRS1998

The Remote Sensing of Mineral Aerosols and Their Impact on Phytoplankton Productivity using Sea WiFS

The main objective of this proposal was to use SeaWiFs data to study the relationship between aerosols found in aeollan dust and photosynthesis of phytoplankton in open ocean surface waters. This project was a collaborative effort between myself and Dr. Neil Tindale at Texas A&M University and followed on our earlier funded proposal which had been designed as a proof-of-concept study to determine if ocean color sensors such as the Coastal Zone Color Scanner (CZCS) could be used to detect and map large-scale mineral aerosol plumes. Despite the large spatial and temporal gaps inherent in the CZCS data coverage, our results from this initial study indicated that an ocean color sensor could indeed be used to detect aerosols. These encouraging results led us to propose in this proposal the use of SeaWiFS data to study mineral aerosol transport and its impact on phytoplankton production. This proposal orignally intended to make use of SeaWiFS images, but as the launch delay of SeaWiFS dragged on, we had to make do with other satellite data sets. Thus, the focus of this proposal became the CSCS image archive instead. I detail my results and accomplishments with this data set.

Stegmann, Petra M.↗
DOE OSTI2020

Impacts of long-range transport of aerosols on marine-boundary-layer clouds in the eastern North Atlantic

Vertical profiles of aerosols are inadequately observed and poorly represented in climate models, contributing to the current large uncertainty associated with aerosol–cloud interactions. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) aircraft field campaign near the Azores islands provided ample observations of vertical distributions of aerosol and cloud properties. Here we utilize the in situ aircraft measurements from the ACE-ENA and ground-based remote-sensing data along with an aerosol-aware Weather Research and Forecast (WRF) model to characterize the aerosols due to long-range transport over a remote region and to assess their possible influence on marine-boundary-layer (MBL) clouds. The vertical profiles of aerosol and cloud properties measured via aircraft during the ACE-ENA campaign provide detailed information revealing the physical contact between transported aerosols and MBL clouds. The European Centre for Medium-Range Weather Forecasts Copernicus Atmosphere Monitoring Service (ECMWF-CAMS) aerosol reanalysis data can reproduce the key features of aerosol vertical profiles in the remote region. The cloud-resolving WRF sensitivity experiments with distinctive aerosol profiles suggest that the transported aerosols and MBL cloud interactions (ACIs) require not only aerosol plumes to get close to the marine-boundary-layer top but also large cloud top height variations. Based on those criteria, the observations show that the occurrence of ACIs involving the transport of aerosol over the eastern North Atlantic (ENA) is about 62 % in summer. For the case with noticeable long-range-transport aerosol effects on MBL clouds, the susceptibilities of droplet effective radius and liquid water content are -0.11 and +0.14, respectively. When varying by a similar magnitude, aerosols originating from the boundary layer exert larger microphysical influence on MBL clouds than those entrained from the free troposphere.

54 ENVIRONMENTAL SCIENCES↗