Airborne Sampling Research Articles

Bulk Scattering Properties for the Remote Sensing of Ice Clouds. Part I: Microphysical Data and Models

Abstract This study reports on the use of in situ data obtained in midlatitude and tropical ice clouds from airborne sampling probes and balloon-borne replicators as the basis for the development of bulk scattering models for use in satellite remote sensing applications. Airborne sampling instrumentation includes the two-dimensional cloud (2D-C), two-dimensional precipitation (2D-P), high-volume precipitation spectrometer (HVPS), cloud particle imager (CPI), and NCAR video ice particle sampler (VIPS) probes. Herein the development of a comprehensive set of microphysical models based on in situ measurements of particle size distributions (PSDs) is discussed. Two parameters are developed and examined: ice water content (IWC) and median mass diameter Dm. Comparisons are provided between the IWC and Dm values derived from in situ measurements obtained during a series of field campaigns held in the midlatitude and tropical regions and those calculated from a set of modeled ice particles used for light-scattering calculations. The ice particle types considered in this study include droxtals, hexagonal plates, solid columns, hollow columns, aggregates, and 3D bullet rosettes. It is shown that no single habit accurately replicates the derived IWC and Dm values, but a mixture of habits can significantly improve the comparison of these bulk microphysical properties. In addition, the relationship between Dm and the effective particle size Deff, defined as 1.5 times the ratio of ice particle volume to projected area for a given PSD, is investigated. Based on these results, a subset of microphysical models is chosen as the basis for the development of ice cloud bulk scattering models in Part II of this study.

Measuring biomass and carbon in delaware using an airborne profiling LIDAR

A portable, inexpensive profiling light detection and ranging (LIDAR) system was used to inventory forests in Delaware, a small state (5205 km2) on the mid-Atlantic seaboard of the USA. Ground and airborne sampling procedures are described, and large-area inventory results are reported and compared to independent estimates. Systematic airborne LIDAR profiling measurements were used (1) to estimate forest merchantable volume, biomass and above-ground carbon statewide; and (2) to estimate impervious surface and open water area. Over 1300 km of laser profiling data acquired along parallel flight lines 4 km apart were analysed. Four explicitly linear models were considered to predict merchantable volume and total above-ground dry biomass. Merchantable volume estimates were within 21% of US Forest Service estimates at the county level and within 1% statewide. Total above-ground dry biomass estimates were within 22% of USFS estimates at the county level and within 16% statewide. LIDAR estimates of percentage impervious area surface for the three counties (Newcastle, Kent and Sussex) were 10.9, 3.4 and 2.8%, respectively, and 4.7% statewide. Comparable estimates developed using 30 m Enhanced Thematic Mapper digital data and mixture modelling were 8.8, 3.5 and 3.9%, respectively, and 4.9% statewide. Laser estimates of open water at the county and state level were comparable to 1997 Geographical Information System (GIS) estimates. Open water estimates based on laser transect data showed the three counties to have 3.0, 2.0 and 4.6% of their county area covered by water, and 3.5% of the state to be covered by open water. Comparable 1997 GIS estimates were 2.6, 2.1 and 4.8% (county), and 3.5% (state), respectively. The results of the study indicate that line intercept sampling techniques can be used in conjunction with a relatively inexpensive, portable airborne laser system to assess multiple resources regionally.

Seasonal distributions of fine aerosol sulfate in the North American Arctic basin during TOPSE

We used the mist chamber/ion chromatography technique to quantify fine aerosol SO4= (<2.7 μm) in the Arctic during the Tropospheric Ozone Production about the Spring Equinox Experiment (TOPSE) with about 2.5 min time resolution. Our effective sample area ranged from 50° to 86°N and 53° to 100°W. The seasonal evolution of fine aerosol sulfate in the Arctic troposphere during TOPSE was consistent with the phenomenon of Arctic haze. Arctic haze has been attributed to pollution from sources in the Arctic and pollution transported meridionally along stable isentropes into the Arctic in geographically broad but vertically narrow bands. These layers became more prevalent at higher altitudes as the season progressed toward summer, and the relevant isentropes are not held so close to the surface. Mean fine particle SO4= mixing ratios during TOPSE in February below 1000 m were elevated (112 pptv) and highly variable (between 28 and 290 pptv) but were significantly lower at higher altitudes (about 40 pptv). As the season progressed, elevated mixing ratios and higher variability were observed at higher altitudes, up to 7 km. In May, mixing ratios at the lowest altitudes declined but still remained higher than in February at all altitudes. The high variability in our measurements likely reflects the vertical heterogeneity of the wintertime Arctic atmosphere as the airborne sampling platform passed in and out of these layers. It is presumed that mixing ratios and variability will continue to decline at all altitudes into the summer as wet deposition processes become important in removing aerosol SO4= from the troposphere.

Aerosol Chemistry, and Light-Scattering and Hygroscopicity Budgets during Outflow from East Asia

During the ACE-Asia field campaign, 41 aerosol filter samples were obtained by airborne sampling over the ocean to the north, south and west of Japan, generally under conditions of outflow from the Asian continent. These samples were analyzed for their water-soluble chemical components, particularly organic species. Suites of inorganic anions, carbohydrates, organic acids and metallic elements were identified and quantified (21 distinct species). Simultaneously, measurements were made of the aerosol hygroscopicity and light scattering. A factor analysis performed on the compositional data identified several sources for the aerosols sampled during the field campaign. Regression of the light-scattering data onto tracers for each of these factors suggests that the aerosol light scattering could be largely attributed to three of these factors: anthropogenic emissions, biomass burning, and soil dust. Similarly, the aerosol hygroscopicity was largely consistent with an empirical mixing model based on past measurements of the hygroscopicity of these individual aerosol types. Limited size-resolved , aerosol composition measurements were also obtained and suggested different sources for various chemical species.

Airborne sampling of aerosol particles: Comparison between surface sampling at Christmas Island and P‐3 sampling during PEM‐Tropics B

Bulk aerosol sampling of soluble ionic compounds from the NASA Wallops Island P‐3 aircraft and a tower on Christmas Island during PEM‐Tropics B provides an opportunity to assess the magnitude of particle losses in the University of New Hampshire airborne bulk aerosol sampling system. We find that most aerosol‐associated ions decrease strongly with height above the sea surface, making direct comparisons between mixing ratios at 30 m on the tower and the lowest flight level of the P‐3 (150 m) open to interpretation. Theoretical considerations suggest that vertical gradients of sea‐salt aerosol particles should show exponential decreases with height. Observed gradients of Na+ and Mg2+, combining the tower observations with P‐3 samples collected below 1 km, are well described by exponential decreases (r values of 0.88 and 0.87, respectively), though the curve fit underestimates average mixing ratios at the surface by 25%. Cascade impactor samples collected on the tower show that >99% of the Na+ and Mg2+ mass is on supermicron particles, 65% is in the 1–6 micron range, and just 20% resides on particles with diameters larger than 9 microns. These results indicate that our airborne aerosol sampling probes must be passing particles up to at least 6 microns with high efficiency. We also observed that nss SO42− and NH4+, which are dominantly on accumulation mode particles, tended to decrease between 150 and 1000 m, but they were often considerably higher at the lowest P‐3 sampling altitudes than at the tower. This finding is presently not well understood.

Characterization of the photooxidant formation in the metropolitan area of Milan from aircraft measurements

[1] Measurements of O3, NO2, HCHO, H2O2, and hydrocarbons were performed on MetAir's airborne sampling platform in the area of Milan within the Italian Po Basin. The objective was to characterize the O3 formation process and its dependence on ambient levels of NOx and volatile organic compounds (VOCs). In the metropolitan area and downwind a regional plume developed of the order of 50 km wide and atop of this an urban plume 10–15 km wide. In the Po Basin, ozone mixing ratios were around 80–130 ppb, while in the regional plume, ozone levels were 15–30 ppb higher. In addition, the urban plume adds another 10–30 ppb. Maximum afternoon ozone mixing ratios reached 195 ppb. Downwind of Milan, ozone strongly increased (0.6–1 ppb km−1), whereas peroxide usually decreased. An observation based budget analysis of the photooxidant formation yielded chemical ozone production rates between 5 and 15 ppb h−1, occasionally exceeding 20 ppb h−1. The chemical peroxide production rate was negligible in the urban and regional plume and small in the adjacent areas. Ozone production rates derived from an observation-driven steady state model were mostly lower than calculated from the budget approach, while peroxide production rates were negligible. Missing VOCs due to incomplete sampling might be responsible for the discrepancies between the model and measurements. The analysis indicates VOC-sensitive ozone formation within and downwind of the metropolitan area of Milan. This would still be the result of the model calculation in the case of doubled VOC levels.

The detection of large HNO3-containing particles in the winter Arctic stratosphere.

Large particles containing nitric acid (HNO3) were observed in the 1999/2000 Arctic winter stratosphere. These in situ observations were made over a large altitude range (16 to 21 kilometers) and horizontal extent (1800 kilometers) on several airborne sampling flights during a period of several weeks. With diameters of 10 to 20 micrometers, these sedimenting particles have significant potential to denitrify the lower stratosphere. A microphysical model of nitric acid trihydrate particles is able to simulate the growth and sedimentation of these large sizes in the lower stratosphere, but the nucleation process is not yet known. Accurate modeling of the formation of these large particles is essential for understanding Arctic denitrification and predicting future Arctic ozone abundances.

Acid gas and metal emission rates during long‐lived basalt degassing at Stromboli Volcano

The discharge of acid gases and metals from Stromboli is determined from airborne and ground‐based filter sampling of particulate matter in the volcanic plume, combined with COSPEC measurements of SO2 fluxes. Smaller particle sizes and high enrichment factors distinguish the most volatile elements (by order: S, Se, Br, Cl, Cd, Bi, In, As, Sb, Sn, F, Au, Pb, Cr, Cu) from those strictly (Fe, Mn, REE, Sc, Sr, Th, Ti, V) or mainly (Al, Ba, Ca, Co, K, Na, U) derived from volcanic ash. Time‐averaged volatile fluxes show that Stromboli is a representative arc emittor, producing 1–2% of the global volcanic budget of sulfur, halogens and several trace metals, while 15–25% of volcanic emissions of Bi, Cd, Cs, Pb and Sn in southern Italy. Subaerial degassing of its S‐Cl‐rich shoshonitic magma over the last 2 ky of similar activity may have released as much copper and gold as is encountered in magma‐derived high‐sulfidation ore deposits.

NOy lifetimes and O3 production efficiencies in urban and power plant plumes: Analysis of field data

In an effort to describe and characterize power plant plumes in the Nashville region, emissions from a small power plant (Gallatin) and a large power plant (Paradise) were examined using data obtained on the Department of Energy G‐1 airborne sampling platform. Observations made on July 3, 7, 15, 17, and 18, 1995, were compiled, and a kinetic analysis of the chemical evolution of the power plant plumes was performed. Analysis of the power plant plume data revealed a very active photochemistry, as had been determined previously for the urban plume. Ozone production efficiencies (OPE), defined as the number of molecules of O3 formed per NOx molecule consumed, were found to be 3 for Gallatin and 2 for Paradise. Lifetimes for NOx (2.8 and 4.2 hours) and NOy (7.0 and 7.7 hours) were determined for Gallatin and Paradise, respectively. These NOx and NOy lifetimes imply rapid loss of NOz (NOz is assumed to be primarily HNO3). Lifetimes for NOz are calculated to be 3 and 2.5 hours for Gallatin and Paradise, respectively. A sensitivity analysis indicates that the Gallatin NOz lifetime could be as long as 5 hours, bringing it into agreement with the value determined for the Nashville urban plume. It is unlikely that the Paradise NOz lifetime is as long as 4 hours. If NOz loss is attributed to dry deposition, a 3 hour lifetime implies a deposition velocity greater than 10 cm s−1, which is much faster than expected based on accepted theory. Possible reasons for this discrepancy are discussed.

Constraints on the age and dilution of Pacific Exploratory Mission‐Tropics biomass burning plumes from the natural radionuclide tracer210Pb

During the NASA Global Troposphere Experiment Pacific Exploratory Mission‐Tropics (PEM‐Tropics) airborne sampling campaign we found unexpectedly high concentrations of aerosol‐associated210Pb throughout the free troposphere over the South Pacific. Because of the remoteness of the study region, we expected specific activities to be generally less than 35 μBq m−3but found an average in the free troposphere of 107 μBq m−3. This average was elevated by a large number of very active (up to 405 μBq m−3) samples that were associated with biomass burning plumes encountered on nearly every PEM‐Tropics flight in the southern hemisphere. We use a simple aging and dilution model, which assumes that222Rn and primary combustion products are pumped into the free troposphere in wet convective systems over fire regions (most likely in Africa), to explain the elevated210Pb activities. This model reproduces the observed210Pb activities very well, and predicts the ratios of four hydrocarbon species (emitted by combustion) to CO to better than 20% in most cases. Plume ages calculated by the model depend strongly on the assumed222Rn activities in the initial plume, but using values plausible for continental boundary layer air yields ages that are consistent with travel times from Africa to the South Pacific calculated with a back trajectory model. The model also shows that despite being easily recognized through the large enhancements of biomass burning tracers, these plumes must have entrained large fractions of the surrounding ambient air during transport.

Risk levels for mite allergens. Are they meaningful?

Allergens found in house dust are among the most common environmental antigens to which man is naturally exposed. Standardized methods for measuring allergen exposure are essential for assessing the relationship between exposure, sensitization, and the severity of asthma. Monoclonal antibody-based assays are the most widely used method for assessing allergen exposure. In the effort to define the best "index of exposure" to mite allergens, several factors need to be investigated, including: 1) whether allergen should be measured in reservoir dust or airborne 2) whether the results of reservoir measurement should be expressed as recovered allergen per unit weight or per unit area. As yet, airborne sampling is insufficiently sensitive to produce reliable and repeatable results. Therefore, measurement of house-dust-mite allergen concentration in reservoir dust should be regarded as the best-validated index of exposure. The results should be expressed and reported both per unit weight (concentration) and per unit area. The strongest predictor of chronic symptoms and acute exacerbation of asthma is sensitization to indoor allergens. A simple dose-response relationship between IgE-mediated hypersensitivity and allergen exposure has been established. For example, exposure to more than 2 microg Group 1 mite allergen/g dust should be regarded as a risk factor for the development of IgE antibody and asthma in susceptible children. The quantitative relationship between exposure and symptoms in patients already sensitized is complex due to a number of possible confounding factors (e.g., other allergens, viruses, asthma medication). A simple threshold level for provocation of asthmatic symptoms has not been clearly defined.

ETEX: A European tracer experiment; observations, dispersion modelling and emergency response

In Autumn, 1994, two releases of perfluorocarbon tracers from north-east France were tracked across northern Europe using a network of 168 ground stations with limited airborne sampling support. Simulating an emergency response situation, modellers from 20 countries reported their long-range dispersion predictions, initially within a few hours of the release and then over the coming days in line with the evolving meteorological data. Subsequent comparison of the predictions with the environmental results showed model performance varying from good, for the conditions of the first release in the majority of cases, to unsatisfactory for the second release in all cases. The experimental database now established represents a unique tool for investigating the effectiveness of future model developments. The papers in this special issue reflect the major scientific results

Airborne studies of aerosol emissions from savanna fires in southern Africa: 2. Aerosol chemical composition

We investigated smoke emissions from fires in savanna, forest, and agricultural ecosystems by airborne sampling of plumes close to prescribed burns and incidental fires in southern Africa. Aerosol samples were collected on glass fiber filters and on stacked filter units, consisting of a Nuclepore prefilter for particles larger than ∼1–2 μm and a Teflon second filter stage for the submicron fraction. The samples were analyzed for soluble ionic components, organic carbon, and black carbon. Onboard the research aircraft, particle number and volume distributions as a function of size were determined with a laser‐optical particle counter and the black carbon content of the aerosol with an aethalometer. We determined the emission ratios (relative to CO2and CO) and emission factors (relative to the amount of biomass burnt) for the various aerosol constituents. The smoke aerosols were rich in organic and black carbon, the latter representing 10–30% of the aerosol mass. K+and NH4+were the dominant cationic species in the smoke of most fires, while Cl−and SO42−were the most important anions. The aerosols were unusually rich in Cl−, probably due to the high Cl content of the semiarid vegetation. Comparison of the element budget of the fuel before and after the fires shows that the fraction of the elements released during combustion is highly variable between elements. In the case of the halogen elements, almost the entire amount released during the fire is present in the aerosol phase, while in the case of C, N, and S, only a small proportion ends up as particulate matter. This suggests that the latter elements are present predominantly as gaseous species in the fresh fire plumes studied here.

A new practical formula for calculating free-stream aerosol particle properties in airborne sampling applications

In this paper, we derive a new formula for determining the free stream aerosol particle size distribution from airborne measurements with a sharp-edged aspirating diffuser sampler backed by a filter. We point out that Computational Fluid Dynamics (CFD) and Computational Particle Dynamics (CPD) can be used to determine the conversion factor for translating the size distribution of particles collected on the filter to the free stream aerosol particle size distribution which is the quantity of interest in airborne aerosol particle sampling.

A new practical formula for calculating free-stream aerosol particle properties in airborne sampling applications

In this paper, we derive a new formula for determining the free stream aerosol particle size distribution from airborne measurements with a sharp-edged aspirating diffuser sampler backed by a filter. We point out that Computational Fluid Dynamics (CFD) and Computational Particle Dynamics (CPD) can be used to determine the conversion factor for translating the size distribution of particles collected on the filter to the free stream aerosol particle size distribution which is the quantity of interest in airborne aerosol particle sampling.

Qualitative and quantitative wind tunnel measurements of the airflow through a shrouded airborne aerosol sampling probe

In this paper, we present the results of a series of wind tunnel tests of the airflow through a shrouded probe designed by Ram et al. (1995, J. Aerosol. Sci. 26 , 945–962) for high velocity airborne sampling of insoluble aerosol particles in the size range 0.1–15 μm diameter. Tests included flow visualization using a laser light-sheet and hot wire anemometry measurements of air velocity profiles within the shroud upstream of the sampling probe with the probe operating at angles of attack from 0 to 15°. We discuss the effectiveness of the shroud in making the flow into the probe isoaxial for situations where the sampler is at small angles of attack and comment on the role of the shroud as an effective flow decelerator. We conclude by comparing the wind tunnel measurements with numerical simulation studies of the airflow through the sampler at 0° angle of attack.

Qualitative and quantitative wind tunnel measurements of the airflow through a shrouded airborne aerosol sampling probe

In this paper, we present the results of a series of wind tunnel tests of the airflow through a shrouded probe designed by Ram et al. (1995, J. Aerosol. Sci. 26, 945–962) for high velocity airborne sampling of insoluble aerosol particles in the size range 0.1–15 μm diameter. Tests included flow visualization using a laser light-sheet and hot wire anemometry measurements of air velocity profiles within the shroud upstream of the sampling probe with the probe operating at angles of attack from 0 to 15°. We discuss the effectiveness of the shroud in making the flow into the probe isoaxial for situations where the sampler is at small angles of attack and comment on the role of the shroud as an effective flow decelerator. We conclude by comparing the wind tunnel measurements with numerical simulation studies of the airflow through the sampler at 0° angle of attack.

Introduction to special section: Southern Oxidants Study Nashville/Middle Tennessee Ozone Study

Journal of Geophysical Research: AtmospheresVolume 103, Issue D17 p. 22209-22212 Free Access Introduction to special section: Southern Oxidants Study Nashville/Middle Tennessee Ozone Study E. B. Cowling, E. B. CowlingSearch for more papers by this authorW. L. Chameides, W. L. ChameidesSearch for more papers by this authorC. S. Kiang, C. S. KiangSearch for more papers by this authorF. C. Fehsenfeld, F. C. FehsenfeldSearch for more papers by this authorJ. F. Meagher, J. F. MeagherSearch for more papers by this author E. B. Cowling, E. B. CowlingSearch for more papers by this authorW. L. Chameides, W. L. ChameidesSearch for more papers by this authorC. S. Kiang, C. S. KiangSearch for more papers by this authorF. C. Fehsenfeld, F. C. FehsenfeldSearch for more papers by this authorJ. F. Meagher, J. F. MeagherSearch for more papers by this author First published: 01 September 1998 https://doi.org/10.1029/98JD01770Citations: 26AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References Chameides, W. L., E. B. Cowling, The State of the Southern Oxidants Study: Policy relevant scientific findings in ozone pollution research 1988–1994, 133, South. Oxidants Study, N. C. State Univ., Raleigh, 1995. Chameides, W. L., R. W. Lindsay, J. Richardson, C. S. Kiang, The role of biogenic hydrocarbons in urban photochemical smog: Atlanta as a case study, Science, 241, 1473– 1475, 1988. Chameides, W. L., R. D. Saylor, E. B. Cowling, Ozone pollution in the rural United States and the new NAAQS, Policy forum, Science, 276, 916, 1997. Fehsenfeld, F. C., J. F. Meagher, E. B. Cowling, Southern Oxidants Study 1993 data analysis workshop report, 92N. C. State Univ., Raleigh, 1993. Hūbler, G., et al.,An overview of the airborne activities during the SOS Nashville/Middle Tennessee Ozone Study,J. Geophys. Res., 103(D17), 1998. Imhoff, R. F., R. Valente, J. F. Meagher, M. Luria, The production of O3 in an urban plume: Airborne sampling of the Atlanta urban plume, Atmos. Environ., 29, 2349– 2358, 1995. McNider, R. T., W. B. Norris, A. J. Song, R. L. Clymer, S. Gupta, R. M. Banta, A. B. White, R. J. Zamora, andM. Trainer, Meteorological conditions during the 1995 SOS Nashville/Middle Tennessee Field Intensive,J. Geophys. Res., 103(D17), 1998. Meagher, J. F., E. B. Cowling, F. C. Fehsenfeld, andW. J. Parkhurst, Ozone formation and transport in the soulheastern United States: An overview of the SOS Nashville/Middle Tennessee Ozone Study,J. Geophys. Res., 103(D17), 1998. , National Research Council (NRC), Rethinking the ozone problem in regional and urban air pollution, 489, Natl. Acad. Press, Washington, D.C., 1991. , Ozone Transport Assessment Group, Executive Report, 59Environmental Council of the States, Washington, D. C., 1997. Rodgers, M. O., W. L. Chameides, Atmospheric photochemical oxidants: A southern perspective, 33, Sch. of Earth and Atmospheric Sciences, Ga. Inst of Technol., Atlanta, Georgia, 1988. Russell, M., Ozone pollution: The hard choices, Science, 241, 1275, 1988. Samson, P., B. Shi, andJ. Milford, A meteorological investigation of high ozone values in American cities, a report to theOff. of Technol. Assess., U. S. Congress, Washington, D.C.,Aug.1988. Solmon, P., E. Cowling, G. Hidy, C. 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Environmental Protection Agency, National Ambient Air Quality Standards for Particulate Matter, Federal Register, 62, 38,901– 39,003, 1997c. Citing Literature Volume103, IssueD1720 September 1998Pages 22209-22212 This article also appears in:Southern Oxidants Study Nashville/Middle Tennessee Ozone Study (SOS)103 ReferencesRelatedInformation

Tropospheric sulfate distribution during SUCCESS: Contributions from jet exhaust and surface sources

The distribution of SO4= aerosol over the central US during SUCCESS indicates that surface sources of SO4= and SO2 in the western US caused SO4= enhancements up to 10 km altitude. The mean (median) SO4= mixing ratio in the mid‐ and upper‐troposphere increased from 24 (16) pptv over the Pacific ocean to 58 (29) pptv over the central plains. Above 10 km the SO4= mixing ratio was essentially the same in both regions, and also when the geographic classifications were further partitioned into upper tropospheric and lower stratospheric categories (mean near 40 pptv). No obvious enhancements of SO4= could be detected in jet exhaust plumes, but this may reflect the difficulty of keeping a large airborne sampling platform within a turbulent wake for time periods longer than a few seconds. Expected SO4= enhancements (based on observed CO2 enhancements and emission factors for these two species) were generally much smaller than the variability of ambient SO4= mixing ratios, so our null result does not mean that aircraft do not emit H2SO4.

Determination of the passing efficiency for aerosol chemical species through a typical aircraft‐mounted, diffuser‐type aerosol inlet system

To assess the particle transmission efficiency of a conventional aircraft‐mounted, diffuser‐type inlet (CI), a new design inlet containing an internal filter basket assembly (aerosol filter inlet, or AFI) was constructed. All interior surfaces of the AFI were covered with filter material, and air was actively pulled through these filter walls during aerosol sampling. The AFI was demonstrated in the laboratory to trap nearly all particles entering its nozzle orifice, so it was considered usable as a baseline to judge the performance of other inlets. Wind tunnel studies were conducted at three different wind velocities that approximated typical research aircraft speeds. As wind velocity increased, particle transmission through the CI relative to the AFI decreased, as evidenced by chemical analysis of the filter deposits. Aircraft studies of the two inlets showed that particle transmission varied significantly with the measured species. Typical coarse‐particle species such as Ca++, Mg++, Na+ and K+ showed 50–90% mass losses through a conventional diffuser‐type inlet/curved intake tube system. Predominantly fine particle species such as SO4= and NH4+ passed the CI system with much higher efficiencies, with aerosol mass losses of 0–26% for most flights. Since the AFI traps nearly all particles aspirated into its nozzle orifice, these values indicate that on average, 80–90% of the SO4= and NH4+ aerosol mass passes through the CI and curved intake tube during airborne sampling. This finding suggests that the capability to sample fine (i.e., submicrometer) aerosols from aircraft is perhaps not as bad as has been previously reported, given that adequate attention is paid to inlet design, location, and orientation issues.