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There are large uncertainties on the radiative forcing from aviation due to a lack of understanding of the aerosol-cloud interactions of aviation-emitted soot. Commercial- and laboratory-generated soot particles have proven to be moderate to potent ice nucleating particles at cirrus temperatures, depending on their morphology and hydrophilicity. However, no studies have quantified the ice nucleation abilities (INAs) of real aircraft engine soot particles mainly due to the challenge of measuring behind an aircraft engine. Here, a series of experiments conducted at an aircraft engine test-cell aiming to quantify the INAs of in-use commercial jet engine soot particles is presented.Soot INAs were characterized with continuous flow diffusion chambers and sampled onto filters and TEM grids for chemical and morphological analysis. The effect of contrail processing (i.e., contrail formation and sublimation) before eventual cirrus formation was investigated by processing the fresh soot in a first ice nucleation chamber set at relevant contrail temperature and relative humidity. The effect of the soot mixing state was assessed by heating the soot to 350°C and stripping off organic and sulfur compounds adsorbed on the soot surface. The results show that fresh aircraft soot mostly nucleate ice homogeneously. Also, contrail processing does not enhance their INAs despite promoting significant morphological restructuring thought to enhance INA. Stripped soot however shows moderate ice nucleation activities, presumably due to an increase in pore availability. Relevant parameterizations will be developed and implemented into global climate models for assessing the indirect effect (if any) of aircraft soot on climate., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Aerosol particles play a critical role as cloud condensation nuclei (CCN) in the atmosphere. The CCN ability is conventionally measured using CCN counters (CCNCs), which determine the proportion of particles that activate into cloud droplets when exposed to water vapor at a pre-set supersaturation. However, recent findings suggest that the co-condensation effect of semi-volatiles can greatly enhance aerosol particle growth, for example, in polluted cities. This co-condensation effect is not captured accurately in conventional CCNCs, such as streamwise CCNC developed by DMT Inc, since the particles are heated as they pass through the CCNC column. To address this limitation, we have developed the Horizontal Cloud Condensation Nuclei Counter (H-CCNC) based on the concept of a continuous-flow thermal-gradient diffusion chamber. The H-CCNC operates at lower temperatures (, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Seven different instruments and measurement methods were used to examine the immersion freezing of bacterial ice nuclei from Snomax® (hereafter Snomax), a product containing ice-active protein complexes from non-viable Pseudomonas syringae bacteria. The experimental conditions were kept as similar as possible for the different measurements. Of the participating instruments, some examined droplets which had been made from suspensions directly, and the others examined droplets activated on previously generated Snomax particles, with particle diameters of mostly a few hundred nanometers and up to a few micrometers in some cases. Data were obtained in the temperature range from −2 to −38 °C, and it was found that all ice-active protein complexes were already activated above −12 °C. Droplets with different Snomax mass concentrations covering 10 orders of magnitude were examined. Some instruments had very short ice nucleation times down to below 1 s, while others had comparably slow cooling rates around 1 K min−1. Displaying data from the different instruments in terms of numbers of ice-active protein complexes per dry mass of Snomax, nm, showed that within their uncertainty, the data agree well with each other as well as to previously reported literature results. Two parameterizations were taken from literature for a direct comparison to our results, and these were a time-dependent approach based on a contact angle distribution (Niedermeier et al., 2014) and a modification of the parameterization presented in Hartmann et al. (2013) representing a time-independent approach. The agreement between these and the measured data were good; i.e., they agreed within a temperature range of 0.6 K or equivalently a range in nm of a factor of 2. From the results presented herein, we propose that Snomax, at least when carefully shared and prepared, is a suitable material to test and compare different instruments for their accuracy of measuring immersion freezing.

Measured ice crystal concentrations in natural clouds at modest supercooling (temperature ~>-10°C) are often orders of magnitude greater than the number concentration of primary ice nucleating particles. Therefore, it has long been proposed that a secondary ice production process must exist that is able to rapidly enhance the number concentration of the ice population following initial primary ice nucleation events. Secondary ice production is important for the prediction of ice crystal concentration and the subsequent evolution of some types of clouds, but the physical basis of the process is not understood and the production rates are not well constrained. In November 2015 an international workshop was held to discuss the current state of the science and future work to constrain and improve our understanding of secondary ice production processes. Examples and recommendations for in situ observations, remote sensing, laboratory investigations, and modeling approaches are presented.

Desert dust is one of the most abundant ice nucleating particle types in the atmosphere. Traditionally, clay minerals were assumed to determine the ice nucleation ability of desert dust and constituted the focus of ice nucleation studies over several decades. Recently some feldspar species were identified to be ice active at much higher temperatures than clay minerals, redirecting studies to investigate the contribution of feldspar to ice nucleation on desert dust. However, so far no study has shown the atmospheric relevance of this mineral phase. For this study four dust samples were collected after airborne transport in the troposphere from the Sahara to different locations (Crete, the Peloponnese, Canary Islands, and the Sinai Peninsula). Additionally, 11 dust samples were collected from the surface from nine of the biggest deserts worldwide. The samples were used to study the ice nucleation behavior specific to different desert dusts. Furthermore, we investigated how representative surface-collected dust is for the atmosphere by comparing to the ice nucleation activity of the airborne samples. We used the IMCA-ZINC setup to form droplets on single aerosol particles which were subsequently exposed to temperatures between 233 and 250K. Dust particles were collected in parallel on filters for offline cold-stage ice nucleation experiments at 253–263K. To help the interpretation of the ice nucleation experiments the mineralogical composition of the dusts was investigated. We find that a higher ice nucleation activity in a given sample at 253K can be attributed to the K-feldspar content present in this sample, whereas at temperatures between 238 and 245K it is attributed to the sum of feldspar and quartz content present. A high clay content, in contrast, is associated with lower ice nucleation activity. This confirms the importance of feldspar above 250K and the role of quartz and feldspars determining the ice nucleation activities at lower temperatures as found by earlier studies for monomineral dusts. The airborne samples show on average a lower ice nucleation activity than the surface-collected ones. Furthermore, we find that under certain conditions milling can lead to a decrease in the ice nucleation ability of polymineral samples due to the different hardness and cleavage of individual mineral phases causing an increase of minerals with low ice nucleation ability in the atmospherically relevant size fraction. Comparison of our data set to an existing desert dust parameterization confirms its applicability for climate models. Our results suggest that for an improved prediction of the ice nucleation ability of desert dust in the atmosphere, the modeling of emission and atmospheric transport of the feldspar and quartz mineral phases would be key, while other minerals are only of minor importance., Atmospheric Chemistry and Physics, 16 (23), ISSN:1680-7375, ISSN:1680-7367

Background: Patients’ experiences regarding the quality of care continue to be a hot topic of discussion in the healthcare industry. Exploring the quality of nursing care from the patients’ perspectives is a vital element of quality evaluation. The purpose of this study was to explore the patients’ perspectives regarding quality nursing care.Methodology: A qualitative descriptive exploratory design was used. A total of twelve participants were recruited from one medical and one surgical unit at a tertiary care hospital in Karachi, Pakistan. Purposive sampling was used to select the participants. Data was collected through semi-structured interviews. A thematic analysis approach was used for data analysis.Results: Data analysis generated three main themes: (1) meaning of QNC, (2) characteristics of nurses, and (3) participants’ recommendations.Conclusion: Nursing care continues to be the foundation of healthcare and QNC could have a great effect on patients’ positive outcome of recovery and well- being. The study also provided vital implications for nursing administrators, practicing nurses, nursing, education, and research.

© 2015 Shahirose S. Premji et al. Preterm birth (PTB) is a final common outcome resulting from many interrelated etiological pathways; of particular interest is antenatal psychosocial distress (i.e., stress, anxiety, and depression). In LMI countries, both exposure to severe life stressors and rate of PTB are on average greater when compared with high-income countries. In LMI countries women are exposed to some of the most extreme psychosocial stress worldwide (e.g., absolute poverty, limited social resources). High prevalence of antenatal stress and depression have been observed in some studies from LMI countries. We propose a psychosocial, biological, and behavioral model for investigating the complex multisystem interactions in stress responses leading to PTB and explain the basis of this approach. We discuss ethical considerations for a psychosocial, biological, and behavioral screening tool to predict PTB from a LMI country perspective.

Immersion freezing is the most relevant heterogeneous ice nucleation mechanism through which ice crystals are formed in mixed-phase clouds. In recent years, an increasing number of laboratory experiments utilizing a variety of instruments have examined immersion freezing activity of atmospherically relevant ice-nucleating particles. However, an intercomparison of these laboratory results is a difficult task because investigators have used different ice nucleation (IN) measurement methods to produce these results. A remaining challenge is to explore the sensitivity and accuracy of these techniques and to understand how the IN results are potentially influenced or biased by experimental parameters associated with these techniques. Within the framework of INUIT (Ice Nuclei Research Unit), we distributed an illite-rich sample (illite NX) as a representative surrogate for atmospheric mineral dust particles to investigators to perform immersion freezing experiments using different IN measurement methods and to obtain IN data as a function of particle concentration, temperature (T), cooling rate and nucleation time. A total of 17 measurement methods were involved in the data intercomparison. Experiments with seven instruments started with the test sample pre-suspended in water before cooling, while 10 other instruments employed water vapor condensation onto dry-dispersed particles followed by immersion freezing. The resulting comprehensive immersion freezing data set was evaluated using the ice nucleation active surface-site density, ns, to develop a representative ns(T) spectrum that spans a wide temperature range (-37 °C < T < -11 °C) and covers 9 orders of magnitude in ns. In general, the 17 immersion freezing measurement techniques deviate, within a range of about 8 °C in terms of temperature, by 3 orders of magnitude with respect to ns. In addition, we show evidence that the immersion freezing efficiency expressed in ns of illite NX particles is relatively independent of droplet size, particle mass in suspension, particle size and cooling rate during freezing. A strong temperature dependence and weak time and size dependence of the immersion freezing efficiency of illite-rich clay mineral particles enabled the ns parameterization solely as a function of temperature. We also characterized the ns(T) spectra and identified a section with a steep slope between -20 and -27 °C, where a large fraction of active sites of our test dust may trigger immersion freezing. This slope was followed by a region with a gentler slope at temperatures below -27 °C. While the agreement between different instruments was reasonable below ~ -27 °C, there seemed to be a different trend in the temperature-dependent ice nucleation activity from the suspension and dry-dispersed particle measurements for this mineral dust, in particular at higher temperatures. For instance, the ice nucleation activity expressed in ns was smaller for the average of the wet suspended samples and higher for the average of the dry-dispersed aerosol samples between about -27 and -18 °C. Only instruments making measurements with wet suspended samples were able to measure ice nucleation above -18 °C. A possible explanation for the deviation between-27 and -18 °C is discussed. Multiple exponential distribution fits in both linear and log space for both specific surface area-based ns(T) and geometric surface area-based ns(T) are provided. These new fits, constrained by using identical reference samples, will help to compare IN measurement methods that are not included in the present study and IN data from future IN instruments.

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-angstrom lesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-angstrom lesund, Svalbard. The campaign's primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications.

International audience

It has been know that aerosol particles act as nuclei for ice formation for over a century and a half (Dufour 1861). Initial attempts to understand the nature of these ice nucleating particles were optical and electron microscope inspection of inclusions at the center of a crystal (Isono 1955; Kumai 1961). Only within the last few decades has instrumentation to extract ice crystals from clouds and analyze the residual material after sublimation of condensed phase water been available [Cziczo and Froyd 2014). Techniques to ascertain the ice nucleating potential of atmospheric aerosols have only been in place for a similar amount of time (DeMott et al. 2011). In this chapter the history of measurements of ice nucleating particles both the field and complementary studies in the laboratory are reviewed. Remaining uncertainties and artifacts associated with measurements are described and suggestions for future areas of improvement are made.