Polarimeter + Lidar–Derived Aerosol Particle Number Concentration

Schlosser, Joseph S.; Stamnes, Snorre; Burton, S. P.; Cairns, Brian; Crosbie, Ewan; Diedenhoven, Bastiaan van; Diskin, G. S.; Dmitrovic, Sanja; Ferrare, R. A.; Hair, Johnathan W.; Hostetler, C. A.; Hu, Yongxiang; Liu, Xu; Moore, Richard H.; Shingler, Taylor; Shook, M.; Thornhill, K. L.; Winstead, Edward L.; Ziemba, L. D.; Sorooshian, Armin

doi:10.3389/frsen.2022.885332

Cited by 13 publications

(28 citation statements)

References 40 publications

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“…Note that the geometric standard deviation factor often exceeds 2 for the in situ observations of number concentrations, while it is generally around 1.5 for the RSP retrievals (see Table S1). Similar comparisons between RSP and LAS number concentrations have been shown by Schlosser et al (2022).…”

Section: Retrieval Of Aerosol Number Concentration In Given Dry Size ...supporting

confidence: 79%

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Remote sensing of aerosol water fraction, dry size distribution and soluble fraction using multi-angle, multi-spectral polarimetry

Diedenhoven

Hasekamp²,

Cairns³

et al. 2022

Atmos. Meas. Tech.

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Abstract. A framework to infer volume water fraction, soluble fraction and dry size distributions of fine-mode aerosol from multi-angle, multi-spectral polarimetry retrievals of column-averaged ambient aerosol properties is presented. The method is applied to observations of the Research Scanning Polarimeter (RSP) obtained during two NASA aircraft campaigns, namely the Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) and the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex). All aerosol retrievals are statistically evaluated using in situ data. Volume water fraction is inferred from the retrieved ambient real part of the refractive index, assuming a dry refractive index of 1.54 and by applying a volume mixing rule to obtain the effective ambient refractive index. The uncertainties in inferred volume water fraction resulting from this simplified model are discussed and estimated to be lower than 0.2 and decreasing with increasing volume water fraction. The daily mean retrieved volume water fractions correlate well with the in situ values with a mean absolute difference of 0.09. Polarimeter-retrieved ambient effective radius for daily data is shown to increase as a function of volume water fraction as expected. Furthermore, the effective variance of the size distributions also increases with increasing effective radius, which we show is consistent with an external mixture of soluble and insoluble aerosol. The relative variations of effective radius and variance over an observation period are then used to estimate the soluble fraction of the aerosol. Daily results of soluble fraction correlate well with in situ-observed sulfate mass fraction with a correlation coefficient of 0.79. Subsequently, inferred water and soluble fractions are used to derive dry fine-mode size distributions from their ambient counterparts. While dry effective radii obtained in situ and from RSP show similar ranges, in situ values are generally substantially smaller during the ACTIVATE deployments, which may be due to biases in RSP retrievals or in the in situ observations, or both. Both RSP and in situ observations indicate the dominance of aerosol with low hygroscopicity during the ACTIVATE and CAMP2Ex campaigns. Furthermore, RSP indicates a high degree of external mixing of particles with low and high hygroscopicity. These retrievals of fine-mode water volume fraction and soluble fraction may be used for the evaluation of water uptake in atmospheric models. Furthermore, the framework allows us to estimate the variation in the concentration of fine-mode aerosol larger than a specific dry radius limit, which can be used as a proxy for the variation in cloud condensation nucleus concentrations. This framework may be applied to multi-angle, multi-spectral satellite data expected to be available in the near future.

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Section: Retrieval Of Aerosol Number Concentration In Given Dry Size ...supporting

confidence: 79%

“…The fine-mode total number concentrations N tot,f are subsequently derived using the approximation (Schlosser et al, 2022)…”

Section: Remote Sensing Observationsmentioning

confidence: 99%

Remote sensing of aerosol water fraction, dry size distribution and soluble fraction using multi-angle, multi-spectral polarimetry

Diedenhoven

Hasekamp²,

Cairns³

et al. 2022

Atmos. Meas. Tech.

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“…Temperature was measured by a Rosemount nondeiced total air temperature sensor (model E102E4AL) with a fastresponse platinum sensing element (Thornhill et al, 2003). This sensor has a 20 m response time and an accuracy of 0.5 deg C. Regions where liquid water content was less than 0.001 gm −3 as derived from a cloud droplet probe (Droplet Measurement Technologies (Sinclair et al, 2019)) were classified as cloud-free (Schlosser et al, 2022).…”

Section: Airborne In Situ Measurementsmentioning

confidence: 99%

Airborne HSRL-2 measurements of elevated aerosol depolarization associated with non-spherical sea salt

Ferrare

Hair

Hostetler

et al. 2023

Front. Remote Sens.

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Airborne NASA Langley Research Center (LaRC) High Spectral Resolution Lidar-2 (HSRL-2) measurements acquired during the recent NASA Earth Venture Suborbital-3 (EVS-3) Aerosol Cloud Meteorology Interactions over the Western Atlantic Experiment (ACTIVATE) revealed elevated particulate linear depolarization associated with aerosols within the marine boundary layer. These observations were acquired off the east coast of the United States during both winter and summer 2020 and 2021 when the HSRL-2 was deployed on the NASA LaRC King Air aircraft. During 20 of 63 total flight days, particularly on days with cold air outbreaks, linear particulate depolarization at 532 nm exceeded 0.15–0.20 within the lowest several hundred meters of the atmosphere, indicating that these particles were non-spherical. Higher values of linear depolarization typically were measured at 355 nm and lower values were measured at 1,064 nm. Several lines of evidence suggest that these non-spherical particles were sea salt including aerosol extinction/backscatter ratio (“lidar ratio”) values of 20–25 sr measured at both 355 and 532 nm by the HSRL-2, higher values of particulate depolarization measured at low (< 60%) relative humidity, coincident airborne in situ size and composition measurements, and aerosol transport simulations. The elevated aerosol depolarization values were not correlated with wind speed but were correlated with salt mass fraction and effective radius of the aerosol when the relative humidity was below 60%. HSRL-2 measured median particulate extinction values of about 20 Mm−1 at 532 nm associated with these non-spherical sea salt particles and found that the aerosol optical depth (AOD) contributed by these particles remained small (0.03–0.04) but represented on average about 30%–40% of the total column AOD. Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) spaceborne lidar aerosol measurements during several cold air outbreaks and CALIOP retrievals of column aerosol lidar ratio using column AOD constraints suggest that CALIOP operational aerosol algorithms can misclassify these aerosols as dusty marine rather than marine aerosols. Such misclassification leads to ∼40–50% overestimates in the assumed lidar ratio and in subsequent retrievals of aerosol optical depth and aerosol extinction.

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“…Level 2 aerosol products (Stamnes et al, 2018;Schlosser et al, 2022) for both the fine and coarse mode include aerosol optical depth, aerosol size distribution parameters (effective radius/variance and number concentration), single scattering albedo (SSA), and complex refractive index, and also ocean properties (ocean diffuse attenuation coefficient, ocean hemispherical backscatter coefficient, chlorophyll-a concentration, surface wind speed) are reported in these files based on a model for open ocean waters (Chowdhary et al, 2006). An aerosol layer height is also retrieved from the RSP observations (e.g., Wu et al, 2016), but we note that the HSRL-2 sensor provides far greater detail regarding the vertical distribution of aerosol particles.…”

Section: Research Scanning Polarimeter (Rsp)mentioning

confidence: 99%

“…Vertically-resolved Na is derived for the first time using the vertically-resolved extinction backscatter coefficient [1/m] measured by HSRL-2 at 532 nm, combined with the column-averaged aerosol extinction cross-section for the fine-mode aerosol retrieved by RSP at 532 nm. The details of this combined lidar-polarimeter algorithm and comparisons against in-situ Na are provided in Schlosser et al (2022). Forthcoming work will summarize additional joint retrieval products that will be archived for public use once they are developed, including retrievals of Nd.…”

Section: Joint Hsrl-2 and Rsp Retrieval Productsmentioning

confidence: 99%

Spatially-coordinated airborne data and complementary products for aerosol, gas, cloud, and meteorological studies: The NASA ACTIVATE dataset

Sorooshian

Alexandrov

Bell

et al. 2023

Preprint

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Abstract. The NASA Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) produced a unique dataset for research into aerosol-cloud-meteorology interactions with applications extending from process-based studies to multi-scale model intercomparison and improvement, and remote sensing algorithm assessments and advancements. ACTIVATE used two NASA Langley Research Center aircraft, a HU-25 Falcon and King Air, to conduct systematic and spatially coordinated flights over the northwest Atlantic Ocean amounting to 162 joint flights and 17 other single-aircraft flights between 2020 and 2022 across all seasons. Data cover 574 and 592 cumulative flights hours for the Falcon and King Air, respectively. The HU-25 Falcon flew conducted profiling at different level legs below, in, and just above boundary layer clouds (< 3 km) and obtained in situ measurements of trace gases, aerosol particles, clouds, and atmospheric state parameters. In cloud-free conditions, the Falcon similarly conducted profiling at different level legs within and immediately above the boundary layer. The King Air (the high-flyer) flew at approximately ~9 km conducting remote sensing with a lidar and polarimeter while also launching dropsondes. Collectively, simultaneous data collected from both aircraft help characterize the same vertical column of the atmosphere. In addition to individual instrument files, data from the Falcon aircraft are combined into “merge files” on the publicly available data archive that are created at different time resolutions of interest (e.g., 1, 5, 10, 15, 30, 60 s, or matching an individual data product start and stop times). This paper describes the ACTIVATE flight strategy, instrument and complementary dataset products, data access and usage details, and data application notes.

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Polarimeter + Lidar–Derived Aerosol Particle Number Concentration

Cited by 13 publications

References 40 publications

Remote sensing of aerosol water fraction, dry size distribution and soluble fraction using multi-angle, multi-spectral polarimetry

Remote sensing of aerosol water fraction, dry size distribution and soluble fraction using multi-angle, multi-spectral polarimetry

Airborne HSRL-2 measurements of elevated aerosol depolarization associated with non-spherical sea salt

Spatially-coordinated airborne data and complementary products for aerosol, gas, cloud, and meteorological studies: The NASA ACTIVATE dataset

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