A likely important feature of the poorly understood aerosol‐cloud interactions over the Southern Ocean (SO) is the dominant role of sea spray aerosol, versus terrestrial aerosol. Ice nucleating ...particles (INPs), or particles required for heterogeneous ice nucleation, present over the SO have not been studied in several decades. In this study, boundary layer aerosol properties and immersion freezing INP number concentrations (nINPs) were measured during a ship campaign that occurred south of Australia (down to 53°S) in March–April 2016. Ocean surface chlorophyll a concentrations ranged from 0.11 to 1.77 mg/m3, and nINPs were a factor of 100 lower than historical surveys, ranging from 0.38 to 4.6 m−3 at −20 °C. The INP population included organic heat‐stable material, with contributions from heat‐labile material. Lower INP source potentials of SO seawater samples compared to Arctic seawater were consistent with lower ice nucleating site densities in this study compared to north Atlantic air masses.
Plain Language Summary
The Southern Ocean is known for a prevalence of clouds that contain both liquid and ice, which are one of the most poorly understood cloud regimes in the climate system. A large gap in understanding important processes in these clouds is a lack of knowledge regarding particles (e.g., sea spray) required for forming ice crystals, termed ice nucleating particles. In a ship‐based monthlong field study, several instruments were deployed in efforts to characterize the ice nucleating particles present over the Southern Ocean for the first time in over four decades. Abundances of ice nucleating particles throughout the voyage were extremely low compared to other ocean regions, and concentrations were 2 orders of magnitude lower than the most recent survey conducted in the 1970s. We report that the ocean‐derived ice nucleating particles observed in this study were organic in nature, supporting a hypothesized link between ice nucleating particles and organic particles associated with phytoplankton blooms. The data from this study provide a desperately needed benchmark for constraining the number of ice crystals that may form in the remote and poorly understood clouds occurring over the Southern Ocean.
Key Points
Number concentrations of ice nucleating particles over the Southern Ocean in March 2016 were a factor of 100 lower than historical surveys
The ice nucleating particle source strength of Southern Ocean seawater was lower than previous measurements in northern hemisphere seawater
Ice nucleation site densities were lower over the Southern Ocean compared to measurements of pristine air masses from other ocean basins
In this study, a shipborne 95 GHz Doppler cloud radar mounted on a stabilized platform is used to retrieve vertical profiles of three-dimensional (3D) winds by sequentially pointing the stabilized ...platform in different directions. A specific challenge is that the maximum angle off zenith is 8∘, which implies that the projection of the horizontal wind components onto the radar beam directions is a small component of Doppler velocity in most cases. A variational 3D wind retrieval technique is then described, allowing for 1 min 3D wind profiles to be retrieved. Statistical comparisons with 3-hourly radiosonde launches from the ship indicate that horizontal wind profiles can be obtained from such cloud radar observations at small off-zenith angles with biases less than 0.2 m s−1 and standard deviations of differences with radiosonde winds less than 2.5 m s−1.
Oceans cover over
70 % of the Earth's surface. Ship-based measurements are an important
component in developing an understanding of atmosphere of this vast region. A
common problem that impacts the ...quality of atmospheric data collected from
marine research vessels is exhaust from both diesel combustion and waste
incineration from the ship itself. Described here is an algorithm, developed
for the recently commissioned Australian blue-water research vessel (RV)
Investigator, that identifies exhaust periods in sampled air. The RV
Investigator, with two dedicated atmospheric laboratories,
represents an unprecedented opportunity for high-quality measurements of the
marine atmosphere. The algorithm avoids using ancillary data such as wind
speed and direction, and instead utilises components of the exhaust itself –
aerosol number concentration, black carbon concentration, and carbon monoxide
and carbon dioxide mixing ratios. The exhaust signal is identified within
each of these parameters individually before they are combined and an
additional window filter is applied. The algorithm relies heavily on
statistical methods, rather than setting thresholds that are too rigid to
accommodate potential temporal changes. The algorithm is more effective than
traditional wind-based filters in removing exhaust data without removing
exhaust-free data, which commonly occurs with traditional filters. In
application to the current dataset, the algorithm identifies 26 % of the
wind filter's “clean” data as exhaust, and recovers 5 % of data falsely
removed by the wind filter. With suitable testing, the algorithm has the
potential to be applied to other ship-based atmospheric measurements where
suitable measurements exist.
This study aimed to validate a wearable device's walking speed estimation pipeline, considering complexity, speed, and walking bout duration. The goal was to provide recommendations on the use of ...wearable devices for real-world mobility analysis. Participants with Parkinson's Disease, Multiple Sclerosis, Proximal Femoral Fracture, Chronic Obstructive Pulmonary Disease, Congestive Heart Failure, and healthy older adults (n = 97) were monitored in the laboratory and the real-world (2.5 h), using a lower back wearable device. Two walking speed estimation pipelines were validated across 4408/1298 (2.5 h/laboratory) detected walking bouts, compared to 4620/1365 bouts detected by a multi-sensor reference system. In the laboratory, the mean absolute error (MAE) and mean relative error (MRE) for walking speed estimation ranged from 0.06 to 0.12 m/s and - 2.1 to 14.4%, with ICCs (Intraclass correlation coefficients) between good (0.79) and excellent (0.91). Real-world MAE ranged from 0.09 to 0.13, MARE from 1.3 to 22.7%, with ICCs indicating moderate (0.57) to good (0.88) agreement. Lower errors were observed for cohorts without major gait impairments, less complex tasks, and longer walking bouts. The analytical pipelines demonstrated moderate to good accuracy in estimating walking speed. Accuracy depended on confounding factors, emphasizing the need for robust technical validation before clinical application.Trial registration: ISRCTN - 12246987.
Challenges exist in recruiting an international sample of clinicians and researchers to an online survey. Traditional recruitment methods remain relevant but issues such as narrow geographical reach, ...high cost and time intensity limit what can be achieved when aiming to recruit an international, multi-disciplinary sample. Internet-mediated and social media approaches to recruitment and engagement offer new, untested ways of capitalizing upon existing professional networks.
To develop, use and appraise a multi-modal recruitment strategy for an online, international survey regarding the management of shoulder pain.
Traditional recruitment methods were combined with internet-mediated recruitment methods to form a multi-modal recruitment strategy. An overview of the development of this three-month recruitment strategy is provided and the value and role of each strand of the recruitment strategy discussed.
In response to the multi-modal recruitment strategy, data was received from 565 clinicians and researchers from 31 countries (64% UK). Complete data was received from 387 respondents with no demographic differences between respondents who completed, and those who started but did not complete the survey. Over 30% of responses were received within 1 week, 50% within 4 weeks and 81% within 8 weeks.
This study shows the acceptability and international, multidisciplinary reach of a low cost multi-modal recruitment strategy for an online survey of international clinicians and researchers. Incorporating the use of social media proved to be an effective, time and resource-efficient recruitment strategy for this online survey and appeared to enhance clinician engagement. A multimodal recruitment strategy is worthy of consideration for future online surveys of clinicians and researchers.
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