Warren Stanley - Academia.edu (original) (raw)

Papers by Warren Stanley

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

<p>Bioaerosols are particles originating from biological sources. O... more <p>Bioaerosols are particles originating from biological sources. Of these, primary bioaerosol particles (PBAP) are those directly emitted as entities, in parts or as agglomerates of particles such as bacteria, spores or pollen. In the atmosphere, PBAP are important players by acting as cloud condensation nuclei and ice nucleating particles (INP). Their relevance for cloud formation is especially important over pristine marine environments, where PBAP are emitted within sea spray aerosol (SSA) and are expected to contribute significantly to the abundance of INP. However, the emissions and sources of PBAP over oceans remain poorly understood.</p><p>Within this work, we performed a controlled sea spray experiment in the Baltic Sea using a novel single-particle fluorescence and scattering instrument, the Multiparameter Bioaerosol Spectrometer (MBS), in combination with bacterial analysis of aerosol and sea water communities. Using this setup, we successfully identified large PBAP (D > 0.8 µm) within SSA and estimated their emissions to be 1 s<sup>-1</sup>m<sup>-2</sup>. Moreover, 1 out of every 10<sup>4 </sup>particles (D > 0.8 µm) was classified as PBAP. The morphology of large fluorescent SSA showed a clear transition during the campaign. This change was most likely linked to changes in the seawater biogeochemical properties observed during the ship campaign. This change was also observed in changes of the bacterial population of the aerosol and seawater, as determined by the 16s rRNA analysis. The bacterial populations were significantly distinct from each other, implying a selective transfer of certain species from seawater to the atmosphere.</p><p>Our results will help to better constrain the emission of PBAP from marine sources to the atmosphere and will help to understand how biogeochemical processes within the sea water can influence particle properties of SSA (e.g. particle morphology).</p><p><em>The content of this work is currently in review at Environmental Science and Technology (ES&T).</em></p>

L'invention concerne un ensemble detecteur de fibres (210, 310, 410, 510) comportant : (i) un... more L'invention concerne un ensemble detecteur de fibres (210, 310, 410, 510) comportant : (i) un corps de chambre a diffusion ; (ii) un moyen permettant d'attirer des particules au travers dudit corps de chambre sous la forme d'un flux de particules, ledit moyen etant adapte de sorte que les particules ont tendance a avancer en une seule file, l'axe longitudinal des particules de forme allongee etant sensiblement aligne sur la direction du flux ; (iii) un moyen permettant d'illuminer le flux de particules (212, 312, 412, 413, 512, 513) a l'interieur du corps de chambre ; (iv) un detecteur optique (236, 336, 338, 436, 536, 538) adapte pour intercepter et collecter une partie de la lumiere diffusee par les particules traversant le faisceau d'illumination ; (v) un moyen de traitement de donnees adapte pour capturer et traiter les signaux en provenance du detecteur optique ; l'appareil comportant par ailleurs un moyen permettant d'appliquer un champ magn...

Z. Ulanowski, Paul H. Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Dust layer profiling us... more Z. Ulanowski, Paul H. Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Dust layer profiling using an aerosol dropsonde’, poster presented at the European Geosciences Union General Assembly, Vienna, Austria, 12-17 April, 2015.

Aerosol particle size distributions were measured below and above a tropical rainforest canopy in... more Aerosol particle size distributions were measured below and above a tropical rainforest canopy in Borneo, Malaysia, in June/July 2008 using the WIBS-3: a single particle dual channel fluorescence spectrometer. Material in the size range 0.8-20 µm was characterized according to optical equivalent diameter (D P), morphology and fluorescence at 310-400 nm and 400-600 nm following excitation at 280 nm and 370 nm respectively. Particles fluorescent after both excitations are likely to be fluorescent primary biological aerosol particles (FBAP). Measured FBAP number concentration (N FBAP) at both sites exhibited clear diurnal cycles. The largest variability was observed in the understorey, where N FBAP reached a minimum of 50-100 L −1 in late morning. In mid afternoon it exhibited strong transient fluctuations as large as 4000 L −1 that were followed by sustained concentrations of 1000-2500 L −1 that reduced steadily between midnight and sunrise. Above the canopy FBAP number ranged from 50-100 L −1 during the daytime to 200-400 L −1 at night but did not exhibit the transient enhancements seen in the understorey. The strong FBAP fluctuations were attributed to the release of fungal spores below the canopy and appeared to be linked to elevated relative humidity. The mean FBAP number fraction in the size range 0.8 µm<D P <20 µm was 55% in the understorey and 28% above canopy. A size mode at 2 µm<D P <4 µm appears at both sites and is primarily FBAP, which dominated the coarse (D P ≥2.5 µm) number concentration at both sites, accounting for 75% in the understorey and 57% above the canopy. In contrast, the concentration of non-fluorescent particles

This paper describes an instrument designed to achieve the continuous monitoring of ambient bio-a... more This paper describes an instrument designed to achieve the continuous monitoring of ambient bio-aerosol concentrations. The instrument is a compact, relatively low-cost, UV aerosol spectrometer that monitors and classifies the ambient aerosol by simultaneously recording from individual airborne particles both a 2×2 fluorescence excitation-emission matrix and multi-angle spatial elastic scattering data. The former can indicate the possible presence of specific biological fluorophores within the particle whilst the latter provides an assessment of particle size and shape. Taken together, these parameters can facilitate discrimination between biological and non-biological particles and potentially allow classification of biological particle types. Example measurements are given illustrating magnitude and temporal fluctuations in the biological fraction of aerosol within the Borneo tropical rain forest.

Helen Smith, Zbigniew Ulanowski, Warren Stanley, Paul Kaye, Edwin Hirst, ‘A Universal Cloud and A... more Helen Smith, Zbigniew Ulanowski, Warren Stanley, Paul Kaye, Edwin Hirst, ‘A Universal Cloud and Aerosol Sounding System (UCASS) based on wide angle light scattering’, poster presented at The Aerosol Society Focus Meeting 9: Recent Advances in Aerosol Measurement Technology, London, UK, 5 April, 2016.

A range of miniature, low-cost optical particle counters for characterizing atmospheric particles... more A range of miniature, low-cost optical particle counters for characterizing atmospheric particles has been developed. They are intended for use with disposable balloon-borne radiosondes, dropsondes or in dense ground-based sensor networks. Versions exist that are suitable for determining the size distributions and number concentrations of cloud particles or atmospheric aerosols such as mineral dust or volcanic ash.

Primary biogenic aerosols (PBA) are used by organisms as a means to propagate their genetic mater... more Primary biogenic aerosols (PBA) are used by organisms as a means to propagate their genetic material, either by transport of the organisms themselves, such as bacterial clusters and viruses, or of their reproductive components in the case of fungi and plants that release spores and pollen. Many studies have suggested PBA might be important for initiation of cloud formation and subsequent precipitation evolution by acting as cloud condensation nuclei (CCN) or possibly as ice nuclei (IN). This link is inferred from laboratory studies demonstrating the high activation efficiency of PBA at warm temperatures, coupled with observations that biological particles are ubiquitous in the atmosphere. Despite more than two hundred years of research (e.g. Ehrenberg, 1830) information on the abundance, composition and more importantly the sources and heterogeneity of PBA on global scales is still lacking. The first estimates of global average PBA emission rates based on observations and budget calculations were provided by Elbert et al. (2007). They demonstrate that fungi contribute a major fraction of the observed coarse PBA PM10 mass (particles with diameters between 1-10 m), particularly Acomycota (AAM) and Basidiomycota (ABM) commonly seen in tropical regions. These species discharge their spores via so-called "active wet" mechanisms that eject spores inside liquid droplets. Elbert et al. (2007) estimate a global average spore emission rate for ABM of ~17-50 Tg yr-1, corresponding to a global average abundance of ~1 g m-3 and a net emission rate for all fungal spores of 50 Tg yr-1. Uncertainty in the latter estimate is significant compared to the result, placed at 50-1000 Tg yr-1. Nonetheless, these calculations demonstrate the potential importance of PBA and particularly fungal spores in the tropics, where up to half of the coarse mode particulate loading is PBA, and potentially in the global organic aerosol budget. Data was collected using the WIBS-3: a low-cost, portable single-particle dual channel UV fluorescence spectrometer (Kaye et al., 2008) capable of detecting PBA by inducing fluorescence in two so-called biofluorophores - one present during metabolism and the other an amino acid - in the particle size range 1 m < Dp 2 m. In qualitative agreement with measurements of culturable airborne material in a tropical forest's understory (Gilbert, 2005) a diurnal cycle of PBA number concentration is present, reaching a maximum of ~4000 l-1 at local midnight and falling to ~100 l-1 around midday. The role of the planetary boundary layer's collapse and re-establishment in dictating this variation in is also investigated using LIDAR data. Transient PBA concentration spikes lasting several minutes are superposed on the smooth underlying diurnal variation and occur at similar times each day. Nucleopore filter samples were also taken in-situ and analysed under an Environmental scanning electron microscope (ESEM) in Manchester. The images obtained showed the PBA fraction to be dominated by fungal spores of diameter 2-5 m, from various species including ABM. Since such species tend to release spores in bursts at regular times this appears to account for the PBA concentration spikes.

Zbigniew Ulanowski, Paul Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Cloud characterizati... more Zbigniew Ulanowski, Paul Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Cloud characterization using a particle-counter dropsonde’, poster presented at the European Geosciences Union General Assembly, Vienna, Austria, 12-17 April, 2015.

. Unmanned aerial vehicles (UAVs) have great potential to be utilised as an airborne platform for... more . Unmanned aerial vehicles (UAVs) have great potential to be utilised as an airborne platform for measurement of atmospheric particulates and droplets. In particular, the spatio-temporal resolution of UAV measurements could be of use for the characterisation of aerosol, cloud, and radiation (ACR) interactions, which contribute to the largest uncertainty in the radiative forcing of climate change throughout the industrial era (Zelinka et al., 2014). Due to the infancy of the technique however, UAV-instrument combinations must be extensively validated to ensure the data is of high accuracy and reliability. This paper presents an evaluation of a particular UAV-instrument combination: the FMI-Talon fixed-wing UAV and the UCASS open-path optical particle counter. The performance of the UCASS was previously evaluated on a multi-rotor airframe by Girdwood et al. (2020). However, fixed-wing measurements present certain advantages—namely endurance, platform stability, and maximum altitude. Airflow simulations were utilised to define limiting parameters on UAV sampling—that is, an angle of attack limit of 10° and a minimum airspeed of 20 ms−1—which were then applied retroactively to field campaign data as rejection criteria. The field campaign involved an inter-comparison with reference instrumentation mounted on a research station, which the UAV flew past through stratus cloud. The effective diameter measured by the UAV largely agreed within 2 μm. The droplet number concentration agreed within 15 % on all but 5 profiles. It was concluded that UCASS would benefit from a mechanical redesign to avoid calibration drifts, and UAV attitude variations during measurement should be kept to a minimum.

Conference on Lasers and Electro-Optics (CLEO 2000). Technical Digest. Postconference Edition. TOPS Vol.39 (IEEE Cat. No.00CH37088), 2000

Atmospheric Chemistry and Physics

Atmospheric Chemistry and Physics Discussions, 2014

The behaviour of primary biological aerosols (PBAs) at an elevated, un-polluted North American fo... more The behaviour of primary biological aerosols (PBAs) at an elevated, un-polluted North American forest site was studied using an ultra violet-light induced fluorescence (UV-LIF) measurement technique in conjunction with hierarchical agglomerative cluster analysis (HA-CA). Contemporaneous UV-LIF measurements were made with two wide-band integrated bioaerosol spectrometers, WIBS-3 and WIBS-4, which sampled close to the forest floor and via a continuous vertical profiling system, respectively. Additionally, meteorological parameters were recorded at various heights throughout the forest and used to estimate PBAP (Primary Biological Aerosol Particle) fluxes. HA-CA using data from the two, physically separated WIBS instruments independently yielded very similar cluster solutions. All fluorescent clusters displayed a diurnal minimum at midday at the forest floor with maximum concentration occurring at night. Additionally, the number concentration of each fluorescent cluster was enhanced, to different degrees, during wet periods. A cluster that displayed the greatest enhancement and highest concentration during sustained wet periods appears consistent with behaviour reported for fungal spores. A cluster that appears to be behaviourally consistent with bacteria dominated during dry periods. Fluorescent particle concentrations were found to be greater within the forest canopy than at the forest floor, indicating that the canopy was the main source of these particles rather than the minimal surface vegetation, which appeared to contribute little to overall PBA concentrations at this site. Fluorescent particle concentration was positively correlated with relative humidity (RH), and parameterisations of the aerosol response during dry and wet periods are reported. The aforementioned fungal spore-like cluster displayed a strong positive response to increasing RH. The bacteria-like cluster responded more strongly to direct rainfall events than other PBA types. Peak concentrations of this cluster are shown to be linearly correlated to the log of peak rainfall rates. Parallel studies by Huffman et al. (2013) and Prenni et al. (2013) showed that the fluorescent particle concentrations correlated linearly with ice nuclei (IN) concentrations at this site during rain events. We discuss this result in conjunction with our cluster analysis to appraise the candidate IN.

Atmospheric Chemistry and Physics, 2013

Atmospheric Chemistry and Physics, 2010

Aerosol particle size distributions were measured below and above a tropical rainforest canopy in... more Aerosol particle size distributions were measured below and above a tropical rainforest canopy in Borneo, Malaysia, in June/July 2008 using the WIBS-3: a single particle dual channel fluorescence spectrometer. Material in the size range 0.8-20 µm was characterized according to optical equivalent diameter (D P), morphology and fluorescence at 310-400 nm and 400-600 nm following excitation at 280 nm and 370 nm respectively. Particles fluorescent after both excitations are likely to be fluorescent primary biological aerosol particles (FBAP). Measured FBAP number concentration (N FBAP) at both sites exhibited clear diurnal cycles. The largest variability was observed in the understorey, where N FBAP reached a minimum of 50-100 L −1 in late morning. In mid afternoon it exhibited strong transient fluctuations as large as 4000 L −1 that were followed by sustained concentrations of 1000-2500 L −1 that reduced steadily between midnight and sunrise. Above the canopy FBAP number ranged from 50-100 L −1 during the daytime to 200-400 L −1 at night but did not exhibit the transient enhancements seen in the understorey. The strong FBAP fluctuations were attributed to the release of fungal spores below the canopy and appeared to be linked to elevated relative humidity. The mean FBAP number fraction in the size range 0.8 µm<D P <20 µm was 55% in the understorey and 28% above canopy. A size mode at 2 µm<D P <4 µm appears at both sites and is primarily FBAP, which dominated the coarse (D P ≥2.5 µm) number concentration at both sites, accounting for 75% in the understorey and 57% above the canopy. In contrast, the concentration of non-fluorescent particles

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

&amp;amp;lt;p&amp;amp;gt;Bioaerosols are particles originating from biological sources. O... more &amp;amp;lt;p&amp;amp;gt;Bioaerosols are particles originating from biological sources. Of these, primary bioaerosol particles (PBAP) are those directly emitted as entities, in parts or as agglomerates of particles such as bacteria, spores or pollen. In the atmosphere, PBAP are important players by acting as cloud condensation nuclei and ice nucleating particles (INP). Their relevance for cloud formation is especially important over pristine marine environments, where PBAP are emitted within sea spray aerosol (SSA) and are expected to contribute significantly to the abundance of INP. However, the emissions and sources of PBAP over oceans remain poorly understood.&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;Within this work, we performed a controlled sea spray experiment in the Baltic Sea using a novel single-particle fluorescence and scattering instrument, the Multiparameter Bioaerosol Spectrometer (MBS), in combination with bacterial analysis of aerosol and sea water communities. Using this setup, we successfully identified large PBAP (D &amp;amp;gt; 0.8 &amp;amp;amp;#181;m) within SSA and estimated their emissions to be 1 s&amp;amp;lt;sup&amp;amp;gt;-1&amp;amp;lt;/sup&amp;amp;gt;m&amp;amp;lt;sup&amp;amp;gt;-2&amp;amp;lt;/sup&amp;amp;gt;. Moreover, 1 out of every 10&amp;amp;lt;sup&amp;amp;gt;4 &amp;amp;lt;/sup&amp;amp;gt;particles (D &amp;amp;gt; 0.8 &amp;amp;amp;#181;m) was classified as PBAP. The morphology of large fluorescent SSA showed a clear transition during the campaign. This change was most likely linked to changes in the seawater biogeochemical properties observed during the ship campaign. This change was also observed in changes of the bacterial population of the aerosol and seawater, as determined by the 16s rRNA analysis. The bacterial populations were significantly distinct from each other, implying a selective transfer of certain species from seawater to the atmosphere.&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;Our results will help to better constrain the emission of PBAP from marine sources to the atmosphere and will help to understand how biogeochemical processes within the sea water can influence particle properties of SSA (e.g. particle morphology).&amp;amp;lt;/p&amp;amp;gt;&amp;amp;lt;p&amp;amp;gt;&amp;amp;lt;em&amp;amp;gt;The content of this work is currently in review at Environmental Science and Technology (ES&amp;amp;amp;T).&amp;amp;lt;/em&amp;amp;gt;&amp;amp;lt;/p&amp;amp;gt;

L'invention concerne un ensemble detecteur de fibres (210, 310, 410, 510) comportant : (i) un... more L'invention concerne un ensemble detecteur de fibres (210, 310, 410, 510) comportant : (i) un corps de chambre a diffusion ; (ii) un moyen permettant d'attirer des particules au travers dudit corps de chambre sous la forme d'un flux de particules, ledit moyen etant adapte de sorte que les particules ont tendance a avancer en une seule file, l'axe longitudinal des particules de forme allongee etant sensiblement aligne sur la direction du flux ; (iii) un moyen permettant d'illuminer le flux de particules (212, 312, 412, 413, 512, 513) a l'interieur du corps de chambre ; (iv) un detecteur optique (236, 336, 338, 436, 536, 538) adapte pour intercepter et collecter une partie de la lumiere diffusee par les particules traversant le faisceau d'illumination ; (v) un moyen de traitement de donnees adapte pour capturer et traiter les signaux en provenance du detecteur optique ; l'appareil comportant par ailleurs un moyen permettant d'appliquer un champ magn...

Z. Ulanowski, Paul H. Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Dust layer profiling us... more Z. Ulanowski, Paul H. Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Dust layer profiling using an aerosol dropsonde’, poster presented at the European Geosciences Union General Assembly, Vienna, Austria, 12-17 April, 2015.

Aerosol particle size distributions were measured below and above a tropical rainforest canopy in... more Aerosol particle size distributions were measured below and above a tropical rainforest canopy in Borneo, Malaysia, in June/July 2008 using the WIBS-3: a single particle dual channel fluorescence spectrometer. Material in the size range 0.8-20 µm was characterized according to optical equivalent diameter (D P), morphology and fluorescence at 310-400 nm and 400-600 nm following excitation at 280 nm and 370 nm respectively. Particles fluorescent after both excitations are likely to be fluorescent primary biological aerosol particles (FBAP). Measured FBAP number concentration (N FBAP) at both sites exhibited clear diurnal cycles. The largest variability was observed in the understorey, where N FBAP reached a minimum of 50-100 L −1 in late morning. In mid afternoon it exhibited strong transient fluctuations as large as 4000 L −1 that were followed by sustained concentrations of 1000-2500 L −1 that reduced steadily between midnight and sunrise. Above the canopy FBAP number ranged from 50-100 L −1 during the daytime to 200-400 L −1 at night but did not exhibit the transient enhancements seen in the understorey. The strong FBAP fluctuations were attributed to the release of fungal spores below the canopy and appeared to be linked to elevated relative humidity. The mean FBAP number fraction in the size range 0.8 µm<D P <20 µm was 55% in the understorey and 28% above canopy. A size mode at 2 µm<D P <4 µm appears at both sites and is primarily FBAP, which dominated the coarse (D P ≥2.5 µm) number concentration at both sites, accounting for 75% in the understorey and 57% above the canopy. In contrast, the concentration of non-fluorescent particles

This paper describes an instrument designed to achieve the continuous monitoring of ambient bio-a... more This paper describes an instrument designed to achieve the continuous monitoring of ambient bio-aerosol concentrations. The instrument is a compact, relatively low-cost, UV aerosol spectrometer that monitors and classifies the ambient aerosol by simultaneously recording from individual airborne particles both a 2×2 fluorescence excitation-emission matrix and multi-angle spatial elastic scattering data. The former can indicate the possible presence of specific biological fluorophores within the particle whilst the latter provides an assessment of particle size and shape. Taken together, these parameters can facilitate discrimination between biological and non-biological particles and potentially allow classification of biological particle types. Example measurements are given illustrating magnitude and temporal fluctuations in the biological fraction of aerosol within the Borneo tropical rain forest.

Helen Smith, Zbigniew Ulanowski, Warren Stanley, Paul Kaye, Edwin Hirst, ‘A Universal Cloud and A... more Helen Smith, Zbigniew Ulanowski, Warren Stanley, Paul Kaye, Edwin Hirst, ‘A Universal Cloud and Aerosol Sounding System (UCASS) based on wide angle light scattering’, poster presented at The Aerosol Society Focus Meeting 9: Recent Advances in Aerosol Measurement Technology, London, UK, 5 April, 2016.

A range of miniature, low-cost optical particle counters for characterizing atmospheric particles... more A range of miniature, low-cost optical particle counters for characterizing atmospheric particles has been developed. They are intended for use with disposable balloon-borne radiosondes, dropsondes or in dense ground-based sensor networks. Versions exist that are suitable for determining the size distributions and number concentrations of cloud particles or atmospheric aerosols such as mineral dust or volcanic ash.

Primary biogenic aerosols (PBA) are used by organisms as a means to propagate their genetic mater... more Primary biogenic aerosols (PBA) are used by organisms as a means to propagate their genetic material, either by transport of the organisms themselves, such as bacterial clusters and viruses, or of their reproductive components in the case of fungi and plants that release spores and pollen. Many studies have suggested PBA might be important for initiation of cloud formation and subsequent precipitation evolution by acting as cloud condensation nuclei (CCN) or possibly as ice nuclei (IN). This link is inferred from laboratory studies demonstrating the high activation efficiency of PBA at warm temperatures, coupled with observations that biological particles are ubiquitous in the atmosphere. Despite more than two hundred years of research (e.g. Ehrenberg, 1830) information on the abundance, composition and more importantly the sources and heterogeneity of PBA on global scales is still lacking. The first estimates of global average PBA emission rates based on observations and budget calculations were provided by Elbert et al. (2007). They demonstrate that fungi contribute a major fraction of the observed coarse PBA PM10 mass (particles with diameters between 1-10 m), particularly Acomycota (AAM) and Basidiomycota (ABM) commonly seen in tropical regions. These species discharge their spores via so-called "active wet" mechanisms that eject spores inside liquid droplets. Elbert et al. (2007) estimate a global average spore emission rate for ABM of ~17-50 Tg yr-1, corresponding to a global average abundance of ~1 g m-3 and a net emission rate for all fungal spores of 50 Tg yr-1. Uncertainty in the latter estimate is significant compared to the result, placed at 50-1000 Tg yr-1. Nonetheless, these calculations demonstrate the potential importance of PBA and particularly fungal spores in the tropics, where up to half of the coarse mode particulate loading is PBA, and potentially in the global organic aerosol budget. Data was collected using the WIBS-3: a low-cost, portable single-particle dual channel UV fluorescence spectrometer (Kaye et al., 2008) capable of detecting PBA by inducing fluorescence in two so-called biofluorophores - one present during metabolism and the other an amino acid - in the particle size range 1 m < Dp 2 m. In qualitative agreement with measurements of culturable airborne material in a tropical forest's understory (Gilbert, 2005) a diurnal cycle of PBA number concentration is present, reaching a maximum of ~4000 l-1 at local midnight and falling to ~100 l-1 around midday. The role of the planetary boundary layer's collapse and re-establishment in dictating this variation in is also investigated using LIDAR data. Transient PBA concentration spikes lasting several minutes are superposed on the smooth underlying diurnal variation and occur at similar times each day. Nucleopore filter samples were also taken in-situ and analysed under an Environmental scanning electron microscope (ESEM) in Manchester. The images obtained showed the PBA fraction to be dominated by fungal spores of diameter 2-5 m, from various species including ABM. Since such species tend to release spores in bursts at regular times this appears to account for the PBA concentration spikes.

Zbigniew Ulanowski, Paul Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Cloud characterizati... more Zbigniew Ulanowski, Paul Kaye, Edwin Hirst, Andreas Wieser, Warren Stanley, ‘Cloud characterization using a particle-counter dropsonde’, poster presented at the European Geosciences Union General Assembly, Vienna, Austria, 12-17 April, 2015.

. Unmanned aerial vehicles (UAVs) have great potential to be utilised as an airborne platform for... more . Unmanned aerial vehicles (UAVs) have great potential to be utilised as an airborne platform for measurement of atmospheric particulates and droplets. In particular, the spatio-temporal resolution of UAV measurements could be of use for the characterisation of aerosol, cloud, and radiation (ACR) interactions, which contribute to the largest uncertainty in the radiative forcing of climate change throughout the industrial era (Zelinka et al., 2014). Due to the infancy of the technique however, UAV-instrument combinations must be extensively validated to ensure the data is of high accuracy and reliability. This paper presents an evaluation of a particular UAV-instrument combination: the FMI-Talon fixed-wing UAV and the UCASS open-path optical particle counter. The performance of the UCASS was previously evaluated on a multi-rotor airframe by Girdwood et al. (2020). However, fixed-wing measurements present certain advantages—namely endurance, platform stability, and maximum altitude. Airflow simulations were utilised to define limiting parameters on UAV sampling—that is, an angle of attack limit of 10° and a minimum airspeed of 20 ms−1—which were then applied retroactively to field campaign data as rejection criteria. The field campaign involved an inter-comparison with reference instrumentation mounted on a research station, which the UAV flew past through stratus cloud. The effective diameter measured by the UAV largely agreed within 2 μm. The droplet number concentration agreed within 15 % on all but 5 profiles. It was concluded that UCASS would benefit from a mechanical redesign to avoid calibration drifts, and UAV attitude variations during measurement should be kept to a minimum.

Conference on Lasers and Electro-Optics (CLEO 2000). Technical Digest. Postconference Edition. TOPS Vol.39 (IEEE Cat. No.00CH37088), 2000

Atmospheric Chemistry and Physics

Atmospheric Chemistry and Physics Discussions, 2014

The behaviour of primary biological aerosols (PBAs) at an elevated, un-polluted North American fo... more The behaviour of primary biological aerosols (PBAs) at an elevated, un-polluted North American forest site was studied using an ultra violet-light induced fluorescence (UV-LIF) measurement technique in conjunction with hierarchical agglomerative cluster analysis (HA-CA). Contemporaneous UV-LIF measurements were made with two wide-band integrated bioaerosol spectrometers, WIBS-3 and WIBS-4, which sampled close to the forest floor and via a continuous vertical profiling system, respectively. Additionally, meteorological parameters were recorded at various heights throughout the forest and used to estimate PBAP (Primary Biological Aerosol Particle) fluxes. HA-CA using data from the two, physically separated WIBS instruments independently yielded very similar cluster solutions. All fluorescent clusters displayed a diurnal minimum at midday at the forest floor with maximum concentration occurring at night. Additionally, the number concentration of each fluorescent cluster was enhanced, to different degrees, during wet periods. A cluster that displayed the greatest enhancement and highest concentration during sustained wet periods appears consistent with behaviour reported for fungal spores. A cluster that appears to be behaviourally consistent with bacteria dominated during dry periods. Fluorescent particle concentrations were found to be greater within the forest canopy than at the forest floor, indicating that the canopy was the main source of these particles rather than the minimal surface vegetation, which appeared to contribute little to overall PBA concentrations at this site. Fluorescent particle concentration was positively correlated with relative humidity (RH), and parameterisations of the aerosol response during dry and wet periods are reported. The aforementioned fungal spore-like cluster displayed a strong positive response to increasing RH. The bacteria-like cluster responded more strongly to direct rainfall events than other PBA types. Peak concentrations of this cluster are shown to be linearly correlated to the log of peak rainfall rates. Parallel studies by Huffman et al. (2013) and Prenni et al. (2013) showed that the fluorescent particle concentrations correlated linearly with ice nuclei (IN) concentrations at this site during rain events. We discuss this result in conjunction with our cluster analysis to appraise the candidate IN.

Atmospheric Chemistry and Physics, 2013

Atmospheric Chemistry and Physics, 2010

Aerosol particle size distributions were measured below and above a tropical rainforest canopy in... more Aerosol particle size distributions were measured below and above a tropical rainforest canopy in Borneo, Malaysia, in June/July 2008 using the WIBS-3: a single particle dual channel fluorescence spectrometer. Material in the size range 0.8-20 µm was characterized according to optical equivalent diameter (D P), morphology and fluorescence at 310-400 nm and 400-600 nm following excitation at 280 nm and 370 nm respectively. Particles fluorescent after both excitations are likely to be fluorescent primary biological aerosol particles (FBAP). Measured FBAP number concentration (N FBAP) at both sites exhibited clear diurnal cycles. The largest variability was observed in the understorey, where N FBAP reached a minimum of 50-100 L −1 in late morning. In mid afternoon it exhibited strong transient fluctuations as large as 4000 L −1 that were followed by sustained concentrations of 1000-2500 L −1 that reduced steadily between midnight and sunrise. Above the canopy FBAP number ranged from 50-100 L −1 during the daytime to 200-400 L −1 at night but did not exhibit the transient enhancements seen in the understorey. The strong FBAP fluctuations were attributed to the release of fungal spores below the canopy and appeared to be linked to elevated relative humidity. The mean FBAP number fraction in the size range 0.8 µm<D P <20 µm was 55% in the understorey and 28% above canopy. A size mode at 2 µm<D P <4 µm appears at both sites and is primarily FBAP, which dominated the coarse (D P ≥2.5 µm) number concentration at both sites, accounting for 75% in the understorey and 57% above the canopy. In contrast, the concentration of non-fluorescent particles