Development and Model Application of a Surface-Site-Based Parametrization Framework for Heterogeneous Ice Nucleation

The data base from 11 years of AIDA cloud chamber experiments was used to develop a comprehensive parameterization framework for heterogeneous ice formation. The framework uses the Ice Nucleation Active Surface Site (INAS-) density approach to describe the ice nucleation efficiency for desert dust and soot above and below water saturation. Furthermore, the framework was implemented in the COSMO-ART model and tested for a synoptic cirrus cloud over Texas, U.S. Within this case study, the model results were compared to aircraft measurements of the MACPEX campaign

Do humans and Convolutional Neural Networks attend to similar areas during scene classification: Effects of task and image type

Deep Learning models like Convolutional Neural Networks (CNN) are powerful image classifiers, but what factors determine whether they attend to similar image areas as humans do? While previous studies have focused on technological factors, little is known about the role of factors that affect human attention. In the present study, we investigated how the tasks used to elicit human attention maps interact with image characteristics in modulating the similarity between humans and CNN. We varied the intentionality of human tasks, ranging from spontaneous gaze during categorization over intentional gaze-pointing up to manual area selection. Moreover, we varied the type of image to be categorized, using either singular, salient objects, indoor scenes consisting of object arrangements, or landscapes without distinct objects defining the category. The human attention maps generated in this way were compared to the CNN attention maps revealed by explainable artificial intelligence (Grad-CAM). The influence of human tasks strongly depended on image type: For objects, human manual selection produced maps that were most similar to CNN, while the specific eye movement task has little impact. For indoor scenes, spontaneous gaze produced the least similarity, while for landscapes, similarity was equally low across all human tasks. To better understand these results, we also compared the different human attention maps to each other. Our results highlight the importance of taking human factors into account when comparing the attention of humans and CNN

The Portable Ice Nucleation Experiment (PINE): A new online instrument for laboratory studies and automated long-term field observations of ice-nucleating particles

Atmospheric ice-nucleating particles (INPs) play an important role in determining the phase of clouds, which affects their albedo and lifetime. A lack of data on the spatial and temporal variation of INPs around the globe limits our predictive capacity and understanding of clouds containing ice. Automated instrumentation that can robustly measure INP concentrations across the full range of tropospheric temperatures is needed in order to address this knowledge gap. In this study, we demonstrate the functionality and capacity of the new Portable Ice Nucleation Experiment (PINE) to study ice nucleation processes and to measure INP concentrations under conditions pertinent for mixed-phase clouds, with temperatures from about −10 to about −40 C. PINE is a cloud expansion chamber which avoids frost formation on the cold walls and thereby omits frost fragmentation and related background ice signals during the operation. The development, working principle and treatment of data for the PINE instrument is discussed in detail. We present laboratory-based tests where PINE measurements were compared with those from the established AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Within experimental uncertainties, PINE agreed with AIDA for homogeneous freezing of pure water droplets and the immersion freezing activity of mineral aerosols. Results from a first field campaign conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) observatory in Oklahoma, USA, from 1 October to 14 November 2019 with the latest PINE design (a commercially available PINE chamber) are also shown, demonstrating PINE\u27s ability to make automated field measurements of INP concentrations at a time resolution of about 8 min with continuous temperature scans for INP measurements between −10 and −30 ∘C. During this field campaign, PINE was continuously operated for 45 d in a fully automated and semi-autonomous way, demonstrating the capability of this new instrument to also be used for longer-term field measurements and INP monitoring activities in observatories

Enhanced ice nucleation activity of coal fly ash aerosol particles initiated by ice-filled pores

Ice-nucleating particles (INPs), which are precursors for ice formation in clouds, can alter the microphysical and optical properties of clouds, thereby impacting the cloud lifetimes and hydrological cycles. However, the mechanisms with which these INPs nucleate ice when exposed to different atmospheric conditions are still unclear for some particles. Recently, some INPs with pores or permanent surface defects of regular or irregular geometries have been reported to initiate ice formation at cirrus temperatures via the liquid phase in a two-step process, involving the condensation and freezing of supercooled water inside these pores. This mechanism has therefore been labelled pore condensation and freezing (PCF). The PCF mechanism allows formation and stabilization of ice germs in the particle without the formation of macroscopic ice. Coal fly ash (CFA) aerosol particles are known to nucleate ice in the immersion freezing mode and may play a significant role in cloud formation. In our current ice nucleation experiments with a particular CFA sample (CFA_UK), which we conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) aerosol and cloud simulation chamber at the Karlsruhe Institute of Technology (KIT), Germany, we observed a strong increase (at a threshold relative humidity with respect to ice of 101 %–105 %) in the ice-active fraction for experiments performed at temperatures just below the homogeneous freezing of pure water. This observed strong increase in the ice-active fraction could be related to the PCF mechanism. To further investigate the potential of CFA particles undergoing the PCF mechanism, we performed a series of temperature-cycling experiments in AIDA. The temperature-cycling experiments involve exposing CFA particles to lower temperatures (down to ∼228 K), then warming them up to higher temperatures (238–273 K) before investigating their ice nucleation properties. For the first time, we report the enhancement of the ice nucleation activity of the CFA particles for temperatures up to 263 K, from which we conclude that it is most likely due to the PCF mechanism. This indicates that ice germs formed in the CFA particles\u27 pores during cooling remain in the pores during warming and induce ice crystallization as soon as the pre-activated particles experience ice-supersaturated conditions at higher temperatures; hence, these pre-activated particles show an enhancement in their ice-nucleating ability compared with the scenario where the CFA particles are directly probed at higher temperatures without temporary cooling. The enhancement in the ice nucleation ability showed a positive correlation with the specific surface area and porosity of the particles. On the one hand, the PCF mechanism can play a significant role in mixed-phase cloud formation in a case where the CFA particles are injected from higher altitudes and then transported to lower altitudes after being exposed to lower temperatures. On the other hand, the PCF mechanism could be the prevalent nucleation mode for ice formation at cirrus temperatures rather than the previously acclaimed deposition mode

The impact of mineral dust on cloud formation during the Saharan dust event in April 2014 over Europe

A regional modeling study on the impact of desert dust on cloud formation is presented for a major Saharan dust outbreak over Europe from 2 April to 5 April 2014. The dust event coincided with an extensive and dense cirrus cloud layer, suggesting an influence of dust on atmospheric ice nucleation. Using interactive simulation with the regional dust model COSMO-MUSCAT, we investigate cloud and precipitation representation in the model and test the sensitivity of cloud parameters to dust-cloud and dust-radiation interactions of the simulated dust plume. We evaluate model results with ground-based and space-borne remote sensings of aerosol and cloud properties, as well as the in situ measurements obtained during the ML-CIRRUS aircraft campaign

Efficacy and safety of programmable compared with fixed anti-siphon devices for treating idiopathic normal-pressure hydrocephalus (iNPH) in adults – SYGRAVA: study protocol for a randomized trial

Abstract Background Idiopathic normal-pressure hydrocephalus (iNPH) is a distinct form of dementia, characterized by gait ataxia, cognitive impairment and urinary incontinence. In contrast to all other causes of dementia (e.g., Alzheimer-type and others), ventriculoperitoneal (VP) shunt surgery may offer a curative treatment option to patients. While being a rather low-risk type of surgery, it may cause significant over- or underdrainage complications (e.g., headaches, dizziness, vomiting, intracerebral bleeding, etc.) during posture change. Anti-siphon devices (ASDs) are a group of technically different additional valves used in shunt surgery. They are designed to maintain intraventricular pressure within a normal physiological range regardless of patient position. Fixed ASDs proved to substantially lower the rate of overdrainage complications. No significant differences, however, were noted regarding underdrainage complications. Technical successors of fixed ASDs are programmable ASDs. The aim of this study is to evaluate whether programmable ASDs compared to fixed ASDs are able to avoid both over- and underdrainage complications. Methods/design In this investigator-initiated, multicenter randomized trial, 306 patients are planned to be recruited. Male and female patients aged ≥18 years with iNPH who are eligible for VP shunt surgery and meet all other entry criteria can participate. Patients will be randomized in a balanced 1: 1 fashion to a VP shunt with a programmable valve either supplemented with a fixed ASD, or a programmable ASD. Patients will be followed-up 3, 6 and, on an optional basis, 12 months after surgery. The primary outcome measure is the cumulative incidence of over- or underdrainage 6 months post surgery, as defined by clinical and imaging parameters. Discussion SYGRAVA is the first randomized trial to determine whether programmable ASDs reduce complications of drainage compared to fixed ASDs in patients with iNPH. The results of this study may contribute to health-technology assessment of different valve systems used for VP-shunt surgery, and determination of the future standard of care. Trial registration International Standard Randomised Controlled Trial Number: ISRCTN13838310. Registered on 10 November 2016

Case-based decision support for fault diagnosis: Do salient ratings discourage situation analysis?

In the processing industry, frequent faults call for assistance in diagnosis, and case-based reasoning (CBR) can provide solutions applied by other operators in the past. This study investigated whether salient case ratings promote an uncritical acceptance of solutions. In 2 experiments, subjects diagnosed faults with a simulated CBR system, and ratings were presented in graphical or verbal format. In most trials, the case with the highest rating provided the correct solution, while in catch-trials, it did not. Graphical ratings were hypothesized to speed up solutions but discourage cross-checking and lead to errors in catch-trials. These hypotheses were not confirmed, even though Experiment 2 maximized the incentive of relying on case ratings. While graphical ratings led subjects to start with the most highly rated case, they did not impair situation analysis and accuracy. The results suggest that during fault diagnosis people are not easily misled into overtrusting a CBR system

Comparison of Modeled and Measured Ice Nucleating Particle Composition in a Cirrus Cloud

The contribution of heterogeneous ice nucleation to the formation of cirrus cloud ice crystals is still not well quantified. This results in large uncertainties when predicting cirrus radiative effects and their role in Earth's climate system. The goal of this case study is to simulate the composition, and thus activation conditions, of ice nucleating particles (INPs) to evaluate their contribution to heterogeneous cirrus ice formation in relation to homogeneous ice nucleation. For this, the regional model COSMO-Aerosols and Reactive Trace Gases (COSMO-ART) was used to simulate a synoptic cirrus cloud over Texas on 13 April 2011. The simulated INP composition was then compared to measured ice residual particle (IRP) composition from the actual event obtained during the NASA Midlatitude Airborne Cirrus Properties Experiment (MACPEX) aircraft campaign. These IRP measurements indicated that the dominance of heterogeneous ice nucleation was mainly driven by mineral dust with contributions from a variety of other particle types. Applying realistic activation thresholds and concentrations of airborne transported mineral dust and biomass-burning particles, the model implementing the heterogeneous ice nucleation parameterization scheme of Ullrich et al. is able to reproduce the overall dominating ice formation mechanism in contrast to the model simulation with the scheme of Phillips et al. However, the model showed flaws in reproducing the IRP composition.United States. National Aeronautics and Space Administration (Award NNH14AX25I)United States. National Aeronautics and Space Administration (Grant NNH09ZDA001N-MACPEX)United States. National Aeronautics and Space Administration (Grant NNX11AC07G