29 research outputs found

    The Impact of Ground-Based Glaciogenic Seeding on a Shallow Stratiform Cloud over the Sierra Madre in Wyoming: A Multi-Sensor Study of the 3 March 2012 Case

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    A case study is presented of the impact of ground-based glaciogenic seeding on a shallow, lightly precipitating orographic storm with abundant supercooled cloud droplets, but few ice particles. The storm was observed on 3 March 2012 as part of the AgI (silver iodide) Seeding Cloud Impact Investigating (ASCII) experiment in Wyoming. The cloud base temperature was about -9°C, and cloud tops were at about -16°C. The high concentration of small droplets and low ice particle concentration lead to natural snow growth, mainly by vapor diffusion. The question addressed here is whether the injection of ice nucleating particles (AgI) enhanced snow growth and snowfall. The treated (seeded) period is compared with the preceding untreated (noseeded) period, and natural trends (observed in an adjacent control region) are removed. The main target site, located on a mountain pass at an elevation above cloud base, was impacted by AgI seeding, according to a trace chemistry analysis of freshly fallen snow. Data from three radar systems were used: the Wyoming Cloud Radar, two Ka-band profiling Micro-Rain Radars, and a X-band scanning Doppler-on-Wheels (DOW) radar. Composite data from these radar systems and from gauges in the target area indicate an increase in low-level reflectivity and precipitation rate during seeding. This finding generally agrees with other published ASCII case studies. The increase in reflectivity during seeding in the target area appears to be due mainly to an increase in particle size (aggregation), not number concentration, as suggested by DOW differential reflectivity and by disdrometer and Cloud Particle Imager measurements on the ground

    Simulating the Storm Environment Responsible for Nepal\u27s First Observed Tornado

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    A high-resolution numerical forecast model was used to simulate the meteorological conditions leading up to the March 31st, 2019 severe weather event that produced Nepal\u27s first-ever observed tornado. The sparse meteorologic observations in the region capturing the storm environment limit the ability to anticipate another similar situation should the particular set of conditions present themselves again. This study presents a multifaced view of the storm environment through 1) a synoptic perspective provided by the Global Data Assimilation System (GDAS) reanalysis dataset and 2) a trio of progressively higher resolution one-way nested simulations (12 km–4km–1km) driven by GDAS boundary conditions to more closely examine the storm-scale environment. GDAS data and numerical simulations revealed moderately strong instability throughout the region with CAPE values between 1000 and 2000 J kg−1 K−1 and lifted index values between −4 and −7. Vertical wind profiles featuring little directional shear and moderate velocity shear yielded shear-based convective indices that suggested slight potential for rotating supercell thunderstorms. Within this environment, the 1-km simulation produced strong, rotating convection in nearly the same location and at nearly the same time as the observed tornadic storm. Lastly, an assessment of the limited number of observed historical tornadic events in the region showed that with amply convective available potential energy, the 2019 Nepal tornado environment stood out for the limited vertical directional wind shear present

    On Tanzania’s Precipitation Climatology, Variability, and Future Projection

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    We investigate historical and projected precipitation in Tanzania using observational and climate model data. Precipitation in Tanzania is highly variable in both space and time due to topographical variations, coastal influences, and the presence of lakes. Annual and seasonal precipitation trend analyses from 1961 to 2016 show maximum rainfall decline in Tanzania during the long rainy season in the fall (March–May), and an increasing precipitation trend in northwestern Tanzania during the short rainy season in the spring (September–November). Empirical orthogonal function (EOF) analysis applied to Tanzania’s precipitation patterns shows a stronger correlation with warmer temperatures in the western Indian Ocean than with the eastern-central Pacific Ocean. Years with decreasing precipitation in Tanzania appear to correspond with increasing sea surface temperatures (SST) in the Indian Ocean, suggesting that the Indian Ocean Dipole (IOD) may have a greater effect on rainfall variability in Tanzania than the El Niño-Southern Oscillation (ENSO) does. Overall, the climate model ensemble projects increasing precipitation trend in Tanzania that is opposite with the historical decrease in precipitation. This observed drying trend also contradicts a slightly increasing precipitation trend from climate models for the same historical time period, reflecting challenges faced by modern climate models in representing Tanzania’s precipitation

    Climate of the Weakly-Forced Yet High-Impact Convective Storms Throughout the Ohio River Valley and Mid-Atlantic United States

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    The 1-in-1000-year precipitation event in late June 2016 over West Virginia caused tremendous flooding damage. Like the 2012 mid-Atlantic derecho that blacked out much of the DC area, similar events can be traced to small, mid-tropospheric perturbations (MPs) embedded in the large-scale ridge pattern. Under this “weakly-forced” pattern, severe weather outbreaks commonly occur alongside eastward propagating MPs acting as a triggering mechanism for progressive mesoscale convective systems, which move across the central and eastern US. Forecasting of such weakly-forced yet severe weather events is difficult in both weather and climate timescales. The present diagnostic analysis of the MP climatology is the first step toward developing metrics that can identify and evaluate weakly-forced severe weather outbreaks in multi-model projections. We report a discernable, potentially pronounced subseasonal change in the MP climatology associated with the changing climate of North America. Both sea surface temperatures within the Gulf of Mexico and mid-level high pressure over the central US were found to exhibit strong correlations with MPs. Analysis of regional climate downscaling indicates a projected increase in MP frequency and the associated convective precipitation through the mid twenty-first century

    Use of antimicrobials during the COVID-19 pandemic: a qualitative study among stakeholders in Nepal

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    The COVID-19 pandemic was a major public health threat and the pressure to find curative therapies was tremendous. Particularly in the early critical phase of the pandemic, a lot of empirical treatments, including antimicrobials, were recommended. Drawing on interviews with patients, clinicians and drug dispensers, this article explores the use of antimicrobials for the management of COVID-19 in Nepal. A total of 30 stakeholders (10 clinicians, 10 dispensers and 10 COVID-19 patients) were identified purposively and were approached for an interview. Clinicians and dispensers in three tertiary hospitals in Kathmandu assisted in the recruitment of COVID-19 patients who were undergoing follow-up at an out-patient department. Interviews were audio recorded, translated and transcribed into English, and were analyzed thematically. The respondents report that over-the-counter (OTC) use of antibiotics was widespread during the COVID-19 pandemic in Nepal. This was mostly rooted in patients' attempts to mitigate the potential severity of respiratory illnesses, and the fear of the stigmatization and social isolation linked to being identified as a COVID-19 patient. Patients who visited drug shops and physicians reportedly requested specific medicines including antibiotics. Clinicians reported uncertainty when treating COVID-19 cases that added pressure to prescribe antimicrobials. Respondents from all stakeholder groups recognized the dangers of excessive use of antimicrobials, with some referring to the development of resistance. The COVID-19 pandemic added pressure to prescribe, dispense and overuse antimicrobials, accentuating the pre-existing OTC use of antimicrobials. Infectious disease outbreaks and epidemics warrant special caution regarding the use of antimicrobials and specific policy response
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