Characterizations of Cloud Droplet Shatter Artifacts in Two Airborne Aerosol Inlets

Craig, Lucas; Moharreri, Arash; Schanot, Allen; Rogers, D. C.; Anderson, B. E.; Dhaniyala, Suresh

doi:10.1080/02786826.2013.780648

Cited by 22 publications

(28 citation statements)

References 33 publications

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“…We did not find any dependence on orientation, flight direction, or upwind versus downwind direction relative to the cloud. Theoretically, such particles can also be artifacts, created by droplet fragmentation at the inlet (Weber et al, 1998;Craig et al, 2013). In our case with a true airspeed of 20 m s −1 , aerodynamic breakup will not occur, and impaction breakup would occur only for cloud droplets larger than approximately 26 µm in diameter.…”

Section: Resultsmentioning

confidence: 99%

Observations of new particle formation in enhanced UV irradiance zones near cumulus clouds

et al. 2015

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Abstract. During the CARRIBA (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados) campaign, the interaction between aerosol particles and cloud microphysical properties was investigated in detail, which also includes the influence of clouds on the aerosol formation. During two intensive campaigns in 2010 and 2011, helicopter-borne measurement flights were performed to investigate the thermodynamic, turbulent, microphysical, and radiative properties of trade-wind cumuli over Barbados. During these flights, 91 cases with increased aerosol particle number concentrations near clouds were detected. The majority of these cases are also correlated with enhanced irradiance in the ultraviolet (UV) spectral wavelength range. This enhancement reaches values up to a factor of 3.3 greater compared to background values. Thus, cloud boundaries provide a perfect environment for the production of precursor gases for new particle formation. Another feature of cloud edges is an increased turbulence, which may also enhance nucleation and particle growth. The observed events have a mean length of 100 m, corresponding to a lifetime of less than 300 s. This implies that particles with diameters of at least 7 nm grew several nanometers per minute, which corresponds to the upper end of values in the literature (Kulmala et al., 2004). Such high values cannot be explained by sulfuric acid alone; thus extremely low volatility organic compounds (ELVOCs) are probably involved here.

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Section: Resultsmentioning

confidence: 99%

Observations of new particle formation in enhanced UV irradiance zones near cumulus clouds

et al. 2015

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“…The aircraft inlet used for this study was a submicron aerosol inlet (SMAI) Craig et al, 2013;Moharreri et al, 2014). A detailed explanation of PILS collection is described in detail elsewhere (Orsini et al, 2003;Sorooshian et al, 2006).…”

Section: Pils Collectionmentioning

confidence: 99%

Technical note: An improved approach to determining background aerosol concentrations with PILS sampling on aircraft

Fukami

Sullivan

Fulgham

et al. 2016

Atmospheric Environment

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h i g h l i g h t sBackground distributions of PILS þ offline IC measurements do not necessarily follow parametric statistics. Histograms of background distributions can be fit to lognormal distributions for accurate background determination. This procedure leads to substantially lower calculated limits of detection for ammonium and other inorganic ions. a r t i c l e i n f o Particle-into-Liquid Samplers (PILS) have become a standard aerosol collection technique, and are widely used in both ground and aircraft measurements in conjunction with off-line ion chromatography (IC) measurements. Accurate and precise background samples are essential to account for gas-phase components not efficiently removed and any interference in the instrument lines, collection vials or off-line analysis procedures. For aircraft sampling with PILS, backgrounds are typically taken with in-line filters to remove particles prior to sample collection once or twice per flight with more numerous backgrounds taken on the ground. Here, we use data collected during the Front Range Air Pollution and Photochemistry Experiment (FRAPP E) to demonstrate that not only are multiple background filter samples are essential to attain a representative background, but that the chemical background signals do not follow the Gaussian statistics typically assumed. Instead, the background signals for all chemical components analyzed from 137 background samples (taken from~78 total sampling hours over 18 flights) follow a log-normal distribution, meaning that the typical approaches of averaging background samples and/or assuming a Gaussian distribution cause an over-estimation of background samples e and thus an underestimation of sample concentrations. Our approach of deriving backgrounds from the peak of the lognormal distribution results in detection limits of 0. 25, 0.32, 3.9, 0.17, 0.75 and 0.57 and calcium (Ca 2þ ), respectively. The difference in backgrounds calculated from assuming a Gaussian distribution versus a log-normal distribution were most extreme for NH 4 þ , resulting in a background that was 1.58Âthat determined from fitting a log-normal distribution.

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“…These design features result in cloud particles impacting on the inlet body at reduced speeds relative to forward-facing probes. Craig et al (2013a) show that the SMAI aerosol samples were largely free of shatter when the mean cloud droplet sizes were smaller than ∼ 16 µm. In clouds with large droplet sizes and drizzle drops, the CN concentrations measured by the SMAI were enhanced because of the presence of shatter particles, but the magnitude of enhancement was significantly lower than that observed with forward-facing probes.…”

Section: First Iteration: Base-imentioning

confidence: 99%

“…In clouds with large droplet sizes and drizzle drops, the CN concentrations measured by the SMAI were enhanced because of the presence of shatter particles, but the magnitude of enhancement was significantly lower than that observed with forward-facing probes. The details of the SMAI design and its sampling characteristics are discussed in Craig et al (2013a, b).…”

Section: First Iteration: Base-imentioning

confidence: 99%

“…The HIMIL is a sharp-edge, forward-facing diffuser modular inlet design that can be assembled to provide gas or aerosol sampling (Stith et al, 2009;UCAR, 2011). NCAR's SMAI was initially developed for gas sampling, but was recently shown to have promise as an interstitial aerosol sampler (Craig et al, 2013a, b). The SMAI design has a flow-through cone with a cross-flow sample tube located inside it.…”

Section: First Iteration: Base-imentioning

confidence: 99%

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Aircraft testing of the new Blunt-body Aerosol Sampler (BASE)

et al. 2014

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Abstract. There is limited understanding of the role of aerosols in the formation and modification of clouds, partly due to inadequate data on such systems. Aircraft-based aerosol measurements in the presence of cloud particles have proven to be challenging because of the problem of cloud droplet/ice particle shatter and the generation of secondary artifact particles that contaminate aerosol samples. Recently, the design of a new aircraft inlet, called the Blunt-body Aerosol Sampler (BASE), which enables sampling of interstitial aerosol particles, was introduced. Numerical modeling results and laboratory test data suggested that the BASE inlet should sample interstitial particles with minimal shatter particle contamination. Here, the sampling performance of the inlet is established from aircraft-based measurements. Initial aircraft test results obtained during the PLOWS (Profiling of Winter Storms) campaign indicated two problems with the original BASE design: separated flows around the BASE at high altitudes and a significant shatter problem when sampling in drizzle. The test data were used to improve the accuracy of flow and particle trajectory modeling around the inlet, and the results from the improved flow model were used to guide design modifications of the BASE to overcome the problems identified in its initial deployment. The performance of the modified BASE was tested during the ICE-T (Ice in Clouds Experiment -Tropics) campaign, and the inlet was seen to provide near shatter-free measurements in a wide range of cloud conditions. The initial aircraft test results, design modifications, and the performance characteristics of the BASE relative to another interstitial inlet, the submicron aerosol inlet (SMAI), are presented.

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Characterizations of Cloud Droplet Shatter Artifacts in Two Airborne Aerosol Inlets

Cited by 22 publications

References 33 publications

Observations of new particle formation in enhanced UV irradiance zones near cumulus clouds

Observations of new particle formation in enhanced UV irradiance zones near cumulus clouds

Technical note: An improved approach to determining background aerosol concentrations with PILS sampling on aircraft

Aircraft testing of the new Blunt-body Aerosol Sampler (BASE)

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