Passive Measurements Research Articles

A Review of Energy Efficiency Interventions in Public Buildings

This research provides a comprehensive exploration of energy efficiency dynamics in non-residential public buildings such as schools, swimming pools, hospitals, and museums. Recognizing the distinct energy consumption patterns of each building type, the study accentuates the unique challenges they present, with a particular focus on the continuous and intensive energy demands of hospitals and the unparalleled energy needs of swimming pools. Through an extensive review of various case studies, the research unveils prevailing energy consumption trends, highlighting the role of metrics in assessing energy efficiency and the inherent challenges these metrics face in ensuring uniformity and direct comparability. A core element of this analysis emphasizes the dual nature of technical retrofitting, categorizing interventions into passive and active measures. The research delves into the sustainability imperatives of energy interventions, exploring the economic motivations underpinning retrofit decisions, and the intricate relationship between advanced technological solutions and the behavioral tendencies of building operators and users. Additionally, the study uncovers the influence of external determinants such as climatic factors and government policies in shaping energy consumption in public buildings. In synthesizing these findings, the paper offers insightful recommendations, emphasizing the need for an integrated approach that harmonizes technological innovations with informed operational habits, aiming to optimize energy efficiency in public non-residential buildings.

High-resolution vibroacoustic characterization of DLR’s Falcon 2000LX ISTAR aircraft

In the framework of CleanSky2’s Airframe project DA9, engine tonal noise is a cooperation between Dassault Aviation and DLR. The project aims to enhance the understanding and mitigation of engine-related tonal noise in the aircraft cabin. The presented work was done to get an in-depth understanding of the vibroacoustic behavior of DLR’s Falcon 2000LX ISTAR aircraft. A two and a half weeks long vibroacoustic ground test was conducted utilizing artificial shaker excitation and operational engine excitation. The responses were measured using a roving grid of accelerometers at more than 1200 positions, meaning a subset of about 250 sensors were installed at every given time and then moved along the fuselage in a predetermined way to get a high-resolution measurement of aircrafts fuselage. The accelerometer data were than processed to show operational deflections shapes and calculate experimental structural intensity vector fields to analyze the energy transfer through the structure for optimized placement of active or passive counter measures. Specifically, the transport of tonal frequencies generated by the engines was analyzed.

Improved tropical deep convective cloud detection using MODIS observations with an active sensor trained machine learning algorithm

Tropical deep convective clouds (DCCs) play an essential role in the Earth system. However, separating DCCs from thick anvils with satellite passive measurements is challenging. In this work, a day/night unified tropical DCC detection approach for MODIS observations is developed with a CloudSat active sensor measurement trained machine learning model. This approach combines brightness temperatures (BTs) at 6.7 μm (BT6.7) and 11 μm (BT11) with derived variables describing horizontal structures of DCCs and improves the tropical DCC probability of detection (POD) from 45.0% for the widely-used BT11 < 215 K method to 67.9%, while the false alarm ratio (FAR) decreases from 43.9% to 32.6%. The Heidke skill score (HSS) of the new algorithm is 0.425, which is more than doubled compared to the HSS of the BT11 < 215 K method (0.182). Moreover, the new algorithm has small biases in DCC's total amount and spatial distribution compared with the CloudSat results. The monthly DCC variations from MODIS wide-swath measurements with the new algorithm demonstrate the ability to reliably provide high temporal and spatial resolution DCC distributions to support intra-seasonal to interannual climate variability studies, which the CloudSat narrow-swath measurements lack enough samples to do. Meanwhile, the new algorithm can also be applied to measurements from other satellite passive sensors when BT6.7 and BT11 are available.

Congener-Specific Emissions from Floors and Walls Characterize Indoor Airborne Polychlorinated Biphenyls.

To reconcile the federal regulation of material polychlorinated biphenyl (PCB) concentrations with recently implemented state regulations of airborne PCBs, there is a need to characterize the relationship between PCB emissions from surfaces and air concentrations. We hypothesized that the magnitude and congener distribution of emissions from floors and walls fully account for the airborne PCBs measured in rooms constructed during the height of PCB production and sales. We measured emissions of PCB congeners from various wall and floor materials using polyurethane foam passive emission samplers before and after hexane wiping. Our results revealed that PCB emissions from flooring adequately predicted the magnitude and congener distribution of PCBs observed in the room air. Emissions varied by material within a single building (5 × 103 ng m-2 day-1 from wood panel walls to 3 × 104 ng m-2 day-1 from vinyl tile) and within the same room. Yet congener distributions between material emission PCB profiles and room air PCB profiles were statistically similar. Hexane wiping significantly reduced PCB emissions (>60%), indicating the importance of surface films as an ongoing source of airborne PCBs. The magnitude and congener distribution of material bulk concentrations did not explain that of material emissions or air concentrations. Passive measurements of polychlorinated biphenyl emissions from floors in a university building predict the concentrations of PCBs in room air.

Assessment of community park as social interaction place for rural communities: a case study of Peyi Community Bwari Abuja

This study is focused on the benefits of community park as a place of social interaction in Peyi community, Bwari Abuja. The study examined community parks and their environmental impact as it relates to social interaction. Community parks play a significant role in the society, they provide significant impact to their host communities by enhancing regional development. It boosts the economy, as well as the dynamics of social processes. A mix methods approach of qualitative and quantitative research was adopted for the study using questionnaire, interview guide and observation checklist. A sample size of 150 was considered, adopting the stratified random sampling technique. The result was analyzed using SPSS and the findings are presented in tables and charts. The findings of the study revealed there is a good interaction in Peyi Community Park between people from different social and cultural backgrounds hence the aim of social interaction in the community park was met but about 60% decry poor availability of basic amenities, inadequate spaces provided as well as lack of privacy and overall poor security Architecture in the park. The study concluded that it is necessary for Architects and other building professionals involved in community park designs to consider innovative ways of ensuring safety at night through the use of motion sensitive lighting systems and other passive measures, design consideration for end users and also design to accommodate anticipated population including provision of age appropriate facilities.

Holistic pedestrian safety assessment for average males and females.

An integrated assessment framework that enables holistic safety evaluations addressing vulnerable road users (VRU) is introduced and applied in the current study. The developed method enables consideration of both active and passive safety measures and distributions of real-world crash scenario parameters. The likelihood of a specific virtual testing scenario occurring in real life has been derived from accident databases scaled to European level. Based on pre-crash simulations, it is determined how likely it is that scenarios could be avoided by a specific Autonomous Emergency Braking (AEB) system. For the unavoidable cases, probabilities for specific collision scenarios are determined, and the injury risk for these is determined, subsequently, from in-crash simulations with the VIVA+ Human Body Models combined with the created metamodel for an average male and female model. The integrated assessment framework was applied for the holistic assessment of car-related pedestrian protection using a generic car model to assess the safety benefits of a generic AEB system combined with current passive safety structures. In total, 61,914 virtual testing scenarios have been derived from the different car-pedestrian cases based on real-world crash scenario parameters. Considering the occurrence probability of the virtual testing scenarios, by implementing an AEB, a total crash risk reduction of 81.70% was achieved based on pre-crash simulations. It was shown that 50 in-crash simulations per load case are sufficient to create a metamodel for injury prediction. For the in-crash simulations with the generic vehicle, it was also shown that the injury risk can be reduced by implementing an AEB, as compared to the baseline scenarios. Moreover, as seen in the unavoidable cases, the injury risk for the average male and female is the same for brain injuries and femoral shaft fractures. The average male has a higher risk of skull fractures and fractures of more than three ribs compared to the average female. The average female has a higher risk of proximal femoral fractures than the average male. A novel methodology was developed which allows for movement away from the exclusive use of standard-load case assessments, thus helping to bridge the gap between active and passive safety evaluations.

Understanding Mental Health Clinicians' Perceptions and Concerns Regarding Using Passive Patient-Generated Health Data for Clinical Decision-Making: Qualitative Semistructured Interview Study.

Digital health-tracking tools are changing mental health care by giving patients the ability to collect passively measured patient-generated health data (PGHD; ie, data collected from connected devices with little to no patient effort). Although there are existing clinical guidelines for how mental health clinicians should use more traditional, active forms of PGHD for clinical decision-making, there is less clarity on how passive PGHD can be used. We conducted a qualitative study to understand mental health clinicians' perceptions and concerns regarding the use of technology-enabled, passively collected PGHD for clinical decision-making. Our interviews sought to understand participants' current experiences with and visions for using passive PGHD. Mental health clinicians providing outpatient services were recruited to participate in semistructured interviews. Interview recordings were deidentified, transcribed, and qualitatively coded to identify overarching themes. Overall, 12 mental health clinicians (n=11, 92% psychiatrists and n=1, 8% clinical psychologist) were interviewed. We identified 4 overarching themes. First, passive PGHD are patient driven-we found that current passive PGHD use was patient driven, not clinician driven; participating clinicians only considered passive PGHD for clinical decision-making when patients brought passive data to clinical encounters. The second theme was active versus passive data as subjective versus objective data-participants viewed the contrast between active and passive PGHD as a contrast between interpretive data on patients' mental health and objective information on behavior. Participants believed that prioritizing passive over self-reported, active PGHD would reduce opportunities for patients to reflect upon their mental health, reducing treatment engagement and raising questions about how passive data can best complement active data for clinical decision-making. Third, passive PGHD must be delivered at appropriate times for action-participants were concerned with the real-time nature of passive PGHD; they believed that it would be infeasible to use passive PGHD for real-time patient monitoring outside clinical encounters and more feasible to use passive PGHD during clinical encounters when clinicians can make treatment decisions. The fourth theme was protecting patient privacy-participating clinicians wanted to protect patient privacy within passive PGHD-sharing programs and discussed opportunities to refine data sharing consent to improve transparency surrounding passive PGHD collection and use. Although passive PGHD has the potential to enable more contextualized measurement, this study highlights the need for building and disseminating an evidence base describing how and when passive measures should be used for clinical decision-making. This evidence base should clarify how to use passive data alongside more traditional forms of active PGHD, when clinicians should view passive PGHD to make treatment decisions, and how to protect patient privacy within passive data-sharing programs. Clear evidence would more effectively support the uptake and effective use of these novel tools for both patients and their clinicians.

Optimization of the Parameters of the Magnetizing Device of the Electromagnetic-Acoustic Transducer

Contactless electromagnetic-acoustic transducers have a set of significant advantages over contact transducers, but at the same time they have significant disadvantages that require the development of effective magnetizing devices. Compared to magnetizing devices that are using permanent magnets, electric current magnetization devices are easily removed from the object of testing and cleaned from contamination by metal particles. Unfortunately, such transducers have significant dimensions and weight.A transducer containing a magnetic circuit magnetized by an electric current coil and two independent electromagnetic inductors located in the gap between the central part of the magnetic circuit and the object of testing has been developed. Inductors are two flat coils, each of them has form like a butterfly. The inductor conductors located in the working area have mutually perpendicular directions; they allow exciting and receiving the transversely polarized acoustic waves without rearranging the transducer. In order to reduce the overall dimensions and mass of the transducer, the mass and dimensional parameters of the magnetizing device were optimized for operating conditions when the magnetization of the object of testing and measurement are performed during the active measurement phase. During the passive measurement phase, which is three times longer than the active phase in time, the magnetizing device cools down. The cyclic mode with alternating active and passive phases made it possible to reduce the weight of the transducer by more than 3 times. In the working area of the transducer with a size of 15×15 mm, with a gap of 1 mm between the magnetic field concentrator and the object of testing, a field with a normal component of 2.4 T is created. The transducer has protection of the magnetization device from overheating, and the cyclic mode of operation allows for continuous performance of up to 30 measurements per minute at an ambient temperature of 20 °C.The developed magnetizing device can be used in solving a number of problems of structuroscopy, thickness measurement, flaw detection by electromagnetic-acoustic methods based on accurate measurement of the propagation time of elastic waves in the object of testing.

Indoor radon concentrations in kindergartens in three Bulgarian districts.

This article examines the results of a study of radon concentrations in kindergartens in three districts of north-western Bulgaria. For the period from December 2019 to May 2020, passive radon measurements were accomplished in 1490 premises of 130 kindergartens. The highest arithmetic mean (AM) value of 219Bqm-3 and geometric mean (GM) value of 156Bqm-3 radon concentration were found in the state kindergartens of the Vratsa district. The radon values for the remaining two districts are as follows: Lovech-AM = 156Bqm-3 and GM = 114Bqm-3; Montana-AM = 125Bqm-3 and GM = 88Bqm-3. The effects of various factors on the radon concentration including district, year of building construction, presence of basement, place of premise, wall, and floor interior covering materials, and presence of a ventilation system were investigated. Factor Analysis was used to assess the combined effects of those factors on indoor radon concentration. The results revealed three combinations of the investigated factors: the first combined the district in which the kindergartens were located and the materials used for the floor of the premises, the second combined the year of construction of the building and the presence of a building foundation, and the third combined the rest of the investigated factors. It is concluded that a regional assessment of predictors of radon variability is needed. The walls in kindergartens should not be covered by gypsum, and floors should not be made from materials that can easily develop cracks such as terra cotta. The installation of a ventilation system reduces the radon concentrations in the premises, which is of particular importance in cases where the measured value is above the national reference levels.

Comprehensive renovation of a multi-apartment building in Sweden: techno-economic analysis with respect to different economic scenarios

ABSTRACT A wider deployment of nearly zero energy buildings (NZEBs) is expected to contribute to the transition to a decarbonized and energy-efficient building sector in Europe. This study proposed an integrated energy-economic analysis to exemplify the feasibility of NZEB renovation in temperate climate. A parametric analysis was performed to identify technical building system configurations that give minimum share of renewable energy systems contributing to NZEB level. Final energy savings, global costs and cost-effectiveness of renovating a building to NZEB level are analysed, considering active and passive energy efficiency measures (EEMs). The active EEMs included efficient water taps and heat recovery ventilation, and the passive EEMs encompassed insulations to roof, exterior walls and ground floor, and improvements of windows and doors. The building had initial final energy use of 133 kWh/m2 year for space heating, domestic hot water production (DHW) and facility electricity. The results show that NZEB level is achieved with active and passive EEMs, without renewable energy systems for scenarios with low discount rates and high future energy price escalations. The annual final energy use for space heating, DHW and facility electricity is reduced cost-effectively by 37-54%. Furthermore, increasing size of PV-system enhanced cost-effectiveness by lowering total global costs.

Relationship between the Intermediate Soil State and Settlement Control Measures during Tunnel Construction Undercrossing the Existing Station

Settlement control of existing stations has consistently been a key issue in tunnel construction. Intermediate soil has a significant influence on the settlement of the existing station as a connector between the new tunnel and the existing station which should be considered when selecting settlement control measures. To clarify the relationship between the state of the intermediate soil and the settlement and control measures of the existing station, this study investigated 49 new tunnel projects under existing stations and elucidated the relationship between the settlement and the settlement control measures of the existing station and the intermediate soil. The relationship between the failure of the intermediate soil and the settlement of the existing station was further analyzed by numerical simulation. Lastly, a simple mechanical model of intermediate soil failure was constructed to determine the stress state of the intermediate soil in constructing a tunnel under the existing station to guide the formulation of settlement control measures for the existing station. Hence, when the intermediate soil is completely destroyed, active control measures, such as jack or grouting lifting, should be implemented; when the intermediate soil is partially damaged, passive control measures should be undertaken. Thus, this study can provide a reference for settlement control of tunnels under existing stations.

Rockfall in open pit mines: management of the pit geometry and protection measures design

Rockfall events represent a serious hazard for people, structures, and infrastructures. The phenomenon can occur in several environments, natural and artificial. In surface mining operations, blasting, bench clean-up and scaling can induce rock blocks detachment, compromising operators’ and operations’ safety. The installation of passive mitigation measures coupled with a specific design of the pit geometry can mitigate this risk. The bench height, width, and slope angle, the number of benches, together with the material characterizing the slope, affect in different ways the kinematics of the possible detached blocks. In this paper, a large set of configurations is studied and trajectory analyses are performed to evaluate the influence of each geometrical or material variable. Results are analysed considering blocks kinematics both on the pit floor and at each bench. The findings provide a useful a tool for a preliminary design of pit geometry and mitigation measures. Design charts are proposed for different slope materials, reporting, as function of the total pit height, the blocks stopping distance, their velocity at the pit floor, their passing height and velocity at each bench, for each geometrical configuration. The obtained charts can be effectively implemented in a quantitative risk assessment procedure for mining activities.

Optimising the inherent fire capacity of structures

This paper introduces a structural design optimisation methodology aimed at minimising the consequences of a fire. The methodology considers the trade-off between implementing passive fire protection measures and enhancing a structure’s “inherent fire capacity”, defined as its ability to retain integrity/functionality without additional fire safety measures. The feasibility of the methodology is demonstrated through the fire safety design of a single-span, steel girder bridge. The optimisation process generates multiple Pareto-optimal solutions for minimising the maximum bridge deflection after a given fire exposure time. Passive protection ensures the bridge’s functionality when facing a heavy goods vehicle fire. In the case of exposure to a car fire, solutions requiring fire protection in specific limited girder regions are identified. The decision-making process is further supported by investigating the robustness of the solutions to uncertainties in material properties and the heat flux model.

Study on the anti-floating water level of the underground structure's comprehensive anti-floating

A significant amount of groundwater is in the underground rock and soil, which can exert buoyancy force on the underground structure. In severe cases, this can result in damage, such as cracking of basement walls and arching of floors. Single-using passive anti-floating measures cannot actively reduce the water load of the underground structure when a sudden high water level occurs. Single-using active anti-floating measures may cause environmental problems, and the reliability and durability of the system are difficult to guarantee. This paper adopted the comprehensive anti-floating method of active and passive combination, and the water level distribution function was established based on the measured data of the groundwater depth. The relationship between the normal water level (NWL) and the failure probability of passive anti-floating, which is the starting probability of active anti-floating (SPAA), was obtained. Then, according to the soil properties of the substrate where the active anti-floating system was located, the design service life of the building, the building function, and how the active anti-floating system affected the surrounding environment, assess the harm caused by exceeding the NWL, select the appropriate SPAA, and determine the NWL, which is the anti-floating water level (AWL) of passive anti-floating. Conventional passive anti-floating measures control groundwater below the NWL. When the water level exceeds the NWL, active anti-floating measures of active pressure relief are adopted. Whether groundwater rises or falls, it will not cause structural anti-floating failure. Reasonably selecting the anti-floating program and AWL ensure the underground structure's anti-floating effect to achieve a balance between its safety and economic viability. The new method was theoretically analyzed using measured one-year groundwater depth data from an observation well in Beijing's Fangshan District.

Physical Environment Study on Social Housing Stock in Italian Western Alps for Healthy and Sustainable Communities

Climate change has reduced the comfort of community environments, and there is an urgent need to improve the health and well-being of low-income residents through design and technical measures. Therefore, this paper conducts research in the context of an ongoing social housing renovation project in Aosta, Italy, in a cold winter and hot summer Alpine environment. The study combined interviews, field measurements, and multiple software simulations to analyze the home of an older adult experiencing energy deprivation. The study found that the indoor acoustic environment quality meets the requirements of various sound-related standards. Still, the lighting and thermal environment must be designed to reduce glare and western sun exposure, and the air quality could improve. Residents’ demand for renovation is low technology, low cost, and high comfort. Therefore, suggestions for combining active and passive transformation measures and maximizing the use of climate and resources are proposed. The lighting and thermal environment are optimized based on the green wisdom of the Haylofts building of the Walser family in the Alps: increase ventilation and reduce indoor air age to improve air quality. Overall, a comprehensive assessment of extreme climatic conditions facilitates the quantitative and qualitative study and control of social housing environments, improves occupant comfort, and decarbonizes such social building stock.

Study of radium content and radon exhalation rates in raw building materials used in southern India

As a potential source of indoor radiation arising from radon, a range of building materials (white cement, gray cement, gravel, gypsum, granite, marble, vitrified tile, and brick) were studied for the specific activity of radium and radon gas exhalation rates. The activity of radium was determined using scintillation gamma-ray spectrometry. Exhalation rates were assessed using passive and active measurement methods. Radon mass exhalation rates from powdered building materials and radon surface exhalation rates from slab-type building materials were measured. Activity concentrations of 226Ra in powder and slab-type building materials were found in the range of (1.12 – 14.98) Bqkg−1 and (17 – 308) Bqkg−1, respectively. 222Rn mass exhalation rates (mBqkg−1h−1) from the building materials were in the range of 15.0 ± 0.8 (gray cement) to 1.1 ± 0.1 (gravel). Surface exhalation rates (mBqm−2h−1) for slab-type materials have a range of 317 ± 9 (brick) to 8 ± 2 (marble). Strong positive correlations were found between the specific activity of radium and radon mass exhalation rates (r = 0.9408) and radon surface exhalation rates (r = 0.7167) for building materials investigated. Obtained data indicates that the building materials used influence indoor radon concentration in dwellings.

Wearable and Mobile Technologies for the Evaluation and Treatment of Obsessive-Compulsive Disorder: Scoping Review.

Smartphones and wearable biosensors can continuously and passively measure aspects of behavior and physiology while also collecting data that require user input. These devices can potentially be used to monitor symptom burden; estimate diagnosis and risk for relapse; predict treatment response; and deliver digital interventions in patients with obsessive-compulsive disorder (OCD), a prevalent and disabling psychiatric condition that often follows a chronic and fluctuating course and may uniquely benefit from these technologies. Given the speed at which mobile and wearable technologies are being developed and implemented in clinical settings, a continual reappraisal of this field is needed. In this scoping review, we map the literature on the use of wearable devices and smartphone-based devices or apps in the assessment, monitoring, or treatment of OCD. In July 2022 and April 2023, we conducted an initial search and an updated search, respectively, of multiple databases, including PubMed, Embase, APA PsycINFO, and Web of Science, with no restriction on publication period, using the following search strategy: ("OCD" OR "obsessive" OR "obsessive-compulsive") AND ("smartphone" OR "phone" OR "wearable" OR "sensing" OR "biofeedback" OR "neurofeedback" OR "neuro feedback" OR "digital" OR "phenotyping" OR "mobile" OR "heart rate variability" OR "actigraphy" OR "actimetry" OR "biosignals" OR "biomarker" OR "signals" OR "mobile health"). We analyzed 2748 articles, reviewed the full text of 77 articles, and extracted data from the 25 articles included in this review. We divided our review into the following three parts: studies without digital or mobile intervention and with passive data collection, studies without digital or mobile intervention and with active or mixed data collection, and studies with a digital or mobile intervention. Use of mobile and wearable technologies for OCD has developed primarily in the past 15 years, with an increasing pace of related publications. Passive measures from actigraphy generally match subjective reports. Ecological momentary assessment is well tolerated for the naturalistic assessment of symptoms, may capture novel OCD symptoms, and may also document lower symptom burden than retrospective recall. Digital or mobile treatments are diverse; however, they generally provide some improvement in OCD symptom burden. Finally, ongoing work is needed for a safe and trusted uptake of technology by patients and providers.

Coastal beaver, Chinook, coho, chum salmon and trout response to nearshore changes resulting from diking and large-scale dam removals: synergistic ecosystem engineering and restoration in the coastal zone

In this paper we assess long-term trends and habitat changes to understand the relationships between coastal beaver (Castor canadensis), salmon, shoreline alterations, large-scale dam removals and nearshore ecological restoration. From this work we conclude that the removal of two large scale dams in the Elwha River has benefited beaver use of the coastal zone through water quality changes that allow beaver to re-establish high-quality zones and the expansion of riparian zones that provide extensive new food resources to beaver. However, the lower river hydrodynamic processes continue to be disrupted by a 200-meter earthen dike installed by local government and landowners for flood protection in the Elwha coastal zone in the 1960’s. The dike acts as a driver of lower river geomorphology and has resulted in the formation of a large and persistent lateral bar along the lower river channel. Associated disrupted hydrodynamics are causing a critical coastal zone of the unimpounded lower river side channels to fill in. This channel habitat has decreased by 23%, with an annual average shrinkage rate of 13%, from pre-dam removal size, resulting in a decrease in both quality and quantity of nursery function for juvenile wild fish in a coastal zone that was historically documented to be the highest functioning for endangered juvenile salmon and trout. Inversely, physical changes including improved water quality in the adjacent impounded west side channel and continued expansion of riparian vegetation along the west delta lateral bar benefitted coastal beaver that recolonized the west delta after dam removals. The newly colonized coastal beaver may provide ecological engineering services to offset side channel loss as well as promote continued fish access. However recreational use was found to negatively impact beaver use of the area. We therefore recommend a series of additional ecosystem restoration actions that incorporate beaver as an ecosystem restoration component of the coastal zone. These actions include a public outreach program to encourage passive recreation measures to prevent negative impacts to beaver, and legacy, ecosystem scale restoration projects that reconnect the hydrodynamics of the west delta to complete Elwha ecosystem restoration. Together, these steps, if implemented, will result in a synergistic ecosystem restoration throughout the watershed to the benefit of the coastal ecosystem, including both beaver and salmon, as intended by the large-scale dam removal project.

Polar firn properties in Greenland and Antarctica and related effects on microwave brightness temperatures

Abstract. In studying the mass balance of polar ice sheets, fluctuations in firn density near the surface is a major uncertainty. In this paper, we explore these variations at locations on the Greenland Ice Sheet and at the Dome C location in Antarctica. Borehole in situ measurements, snow radar echoes, microwave brightness temperatures, and modeling results from the Community Firn Model (CFM) are used. It is shown that firn density profiles can be represented using three processes: “long-scale” and “short-scale” density variations and “refrozen layers”. Consistency with this description is observed in the dynamic range of airborne 0.5–2 GHz brightness temperatures and snow radar echo peaks in measurements performed in Greenland in 2017. Based on these insights, a new analytical partially coherent model is implemented to explain the microwave brightness temperatures using the three-scale description of the firn. Short- and long-scale firn processes are modeled as a 3D continuous random medium with finite vertical and horizontal correlation lengths as opposed to past 1D randomly layered medium descriptions. Refrozen layers are described as deterministic sheets with planar interfaces, with the number of refrozen-layer interfaces determined by radar observations. Firn density and correlation length parameters used in forward modeling to match measured 0.5–2 GHz brightness temperatures in Greenland show consistency with similar parameters in CFM predictions. Model predictions also are in good agreement with multi-angle 1.4 GHz vertically and horizontally polarized brightness temperature measured by the Soil Moisture and Ocean Salinity (SMOS) satellite at Dome C, Antarctica. This work shows that co-located active and passive microwave measurements can be used to infer polar firn properties that can be compared with predictions of the CFM. In particular, 0.5–2 GHz brightness temperature measurements are shown to be sensitive to long-scale firn density fluctuations with density standard deviations in the range of 0.01–0.06 g cm−3 and vertical correlation lengths of 6–20 cm.

A unified synergistic retrieval of clouds, aerosols, and precipitation from EarthCARE: the ACM-CAP product

Abstract. ACM-CAP provides a synergistic best-estimate retrieval of all clouds, aerosols, and precipitation detected by the atmospheric lidar (ATLID), cloud-profiling radar (CPR), and multi-spectral imager (MSI) aboard EarthCARE (Earth Cloud Aerosol and Radiation Explorer). While synergistic retrievals are now mature in many contexts, ACM-CAP is unique in that it provides a unified retrieval of all hydrometeors and aerosols. The Cloud, Aerosol, and Precipitation from mulTiple Instruments using a VAriational TEchnique (CAPTIVATE) algorithm allows for a robust accounting of observational and retrieval errors and the contributions of passive and integrated measurements and for enforcing physical relationships between components (e.g. the conservation of precipitating mass flux through the melting layer). We apply ACM-CAP to EarthCARE scenes simulated from numerical weather model forecasts and evaluate the retrievals against “true” quantities from the numerical model. The retrievals are well-constrained by observations from active and passive instruments and overall closely resemble the bulk quantities (e.g. cloud water content, precipitation mass flux, and aerosol extinction) and microphysical properties (e.g. cloud effective radius and median volume diameter) from the model fields. The retrieval performs best where the active instruments have a strong and unambiguous signal, namely in ice clouds and snow, which is observed by both ATLID and CPR, and in light to moderate rain, where the CPR signal is strong. In precipitation, CPR's Doppler capability permits enhanced retrievals of snow particle density and raindrop size. In complex and layered scenes where ATLID is obscured, we have shown that making a simple assumption about the presence and vertical distribution of liquid cloud in rain and mixed-phase clouds allows improved assimilation of MSI solar radiances. In combination with a constraint on the CPR path-integrated attenuation from the ocean surface, this leads to improved retrievals of both liquid cloud and rain in midlatitude stratiform precipitation. In the heaviest precipitation, both active instruments are attenuated and dominated by multiple scattering; in these situations, ACM-CAP provides a seamless retrieval of cloud and precipitation but is subject to a high degree of uncertainty. ACM-CAP's aerosol retrieval is performed in hydrometeor-free parts of the atmosphere and constrained by ATLID and MSI solar radiances. While the aerosol optical depth is well-constrained in the test scenes, there is a high degree of noise in the profiles of extinction. The use of numerical models to simulate test scenes has helped to showcase the capabilities of the ACM-CAP clouds, aerosols, and precipitation product ahead of the launch of EarthCARE.