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Abstract. Measurements during episodes of African dust, made with two wideband integrated bioaerosol spectrometers (WIBSs), one on the northeastern coast of Puerto Rico and the other in the city of León, Spain, show unmistakable, bioaerosol-like fluorescing aerosol particles (FAPs) that can be associated with these dust episodes. The Puerto Rico event occurred during a major incursion of African dust during June 2020. The León event occurred in the late winter and spring of 2022, when widespread, elevated layers of dust inundated the Iberian Peninsula. Satellite and back-trajectory analyses confirm that dust from northern Africa was the source of the particles during both events. The WIBSs measure the size of individual particles in the range from 0.5 to 30 µm, derive a shape factor, and classify seven types of fluorescence from the FAPs. In general, it is not possible to directly determine the specific biological identity from fluorescence signatures; however, measurements of these types of bioaerosols in laboratory studies allow us to compare ambient fluorescence patterns with whole microbial cells measured under controlled conditions. Here we introduce some new metrics that offer a more quantitative approach for comparing FAP characteristics derived from particles measured under different environmental conditions. The analysis highlights the similarities and differences at the two locations and reveals differences that can be attributed to the age and history of the dust plumes, e.g., the amount of time that the air masses were in the mixed layer and the frequency of precipitation along the air mass trajectory. 

Abstract. Many atmospheric aerosols are cloud condensation nuclei (CCN), capable ofactivating as cloud droplets when the relative humidity exceeds 100 %.Some primary biological aerosol particles (PBAPs), such as plant spores,pollen, or bacteria, have been identified as such CCN. Urban environmentsare a source of these bioaerosols, some of which are naturally produced by thelocal flora or are transported from surrounding regions and others of whichare a result of human activities. In the latter case, open sewage, uncoveredgarbage, mold or other products of such activities can be a source of PBAPs.There have been relatively few studies, especially in the tropics, wherePBAPs and CCN have been simultaneously studied to establish a causal linkbetween the two. The metropolis of San Juan, Puerto Rico, is one such urbanarea with a population of 2 448 000 people (as of 2020). To betterunderstand the fluorescent characteristics and cloud-forming efficiency ofaerosols in this region, measurements with a wideband integrated bioaerosolspectrometer (WIBS), a condensation nuclei (CN) counter and a CCNspectrometer were made at the University of Puerto Rico – Río PiedrasCampus. Results show that the CCN / CN activation ratio and the fraction offluorescing aerosol particles (FAPs) have repetitive daily trends when theFAP fraction is positively correlated with relative humidity and negativelycorrelated with wind speed, consistent with previous studies of fungi sporescollected on substrates. The results from this pilot study highlight the capabilities ofultraviolet-induced fluorescence (UV-IF) measurements for characterizing theproperties of FAPs as they relate to the daily evolution of PBAPs. The use ofmultiple excitation and emission wavelengths, along with shape detection,allows the differentiation of different PBAP types. These measurements,evaluated with respect to previous, substrate-based analysis of the localfungal and pollen spores, have established a preliminary database ofmeasurements that future, longer-term studies will build upon. 

Abstract A multi-agency succession of field campaigns was conducted in southeastern Texas during July 2021 through October 2022 to study the complex interactions of aerosols, clouds and air pollution in the coastal urban environment. As part of the Tracking Aerosol Convection interactions Experiment (TRACER), the TRACER- Air Quality (TAQ) campaign the Experiment of Sea Breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) and the Convective Cloud Urban Boundary Layer Experiment (CUBE), a combination of ground-based supersites and mobile laboratories, shipborne measurements and aircraft-based instrumentation were deployed. These diverse platforms collected high-resolution data to characterize the aerosol microphysics and chemistry, cloud and precipitation micro- and macro-physical properties, environmental thermodynamics and air quality-relevant constituents that are being used in follow-on analysis and modeling activities. We present the overall deployment setups, a summary of the campaign conditions and a sampling of early research results related to: (a) aerosol precursors in the urban environment, (b) influences of local meteorology on air pollution, (c) detailed observations of the sea breeze circulation, (d) retrieved supersaturation in convective updrafts, (e) characterizing the convective updraft lifecycle, (f) variability in lightning characteristics of convective storms and (g) urban influences on surface energy fluxes. The work concludes with discussion of future research activities highlighted by the TRACER model-intercomparison project to explore the representation of aerosol-convective interactions in high-resolution simulations.