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Robustness of atmospheric trace gas retrievals obtained from low-spectral-resolution Fourier transform infrared absorption spectra under variations of interferogram length
Full text linkThis study examines the sensitivity of atmospheric trace gas column retrievals from ground-based Fourier transform interferometer measurements to variations in the number of points in the recorded interferograms. Shortening an interferogram can be part of standard FTIR data processing and typically occurs with a convolution operation on the interferogram. Shortening will alter the leakage pattern in the associated spectrum, and we demonstrate that the removal of a relatively small number of points from the interferogram edges creates a beat pattern in the difference of the associated spectra obtained from the original and shortened interferograms. For low-spectral-resolution interferometers, the beat pattern may exceed the spectral noise level, and, if this occurs, the number of points in the interferogram can become a strong influence parameter for the retrieved trace gas. In a case study with formaldehyde retrievals obtained from low-resolution spectra in Sodankylä and Kolkata, we show that the retrieval software does not accurately model the leakage pattern and that interferogram shortening has a large effect on atmospheric gas column retrievals that exceeds the estimated retrieval uncertainty of approximately 15 %–30 %. This sensitivity of the retrieval algorithm to the length of the underlying low-resolution interferogram can be reduced by applying a nontrivial apodization such as Norton–Beer apodization. For the Sodankylä case study the correlation between formaldehyde columns obtained from low- and high-resolution measurements increased from 0.72 (without apodization) to 0.93 (Norton–Beer strong apodization)
Modeling the intermittent lava lake drops occurring between 2015 and 2021 at Nyiragongo volcano
No full textBetween 2015 and 2021, Nyiragongo's lava lake level experienced a linear increase punctuated by fast intermittent drops. These drops occurred synchronously to seismic swarm at approximately 15 km below the surface and extending laterally NE from the volcano. To interpret these lava lake level patterns in terms of reservoirs pressure evolution within Nyiragongo, we consider the following simplified plumbing system: a central reservoir is fed by a constant flux of magma, distributing the fluid up into the lava lake and laterally into a distal storage zone. Magma transport is driven by a pressure gradient between the magma storage bodies, accommodating influx and outflow of magma elastically, and the lava lake. Lateral transport at depth occurs through a hydraulic connection for which the flow resistance is coupled to the magma flux. When the right conditions are met, lateral magma transport occurs intermittently and triggers intermittent lava lake level drops matching the observations
Thermal fertility limits of the Mediterranean fruit fly, <i>Ceratitis capitata </i>(Wiedemann) (Diptera: Tephritidae)
No full textAn Exactly Energy-conserving Electromagnetic Particle-in-cell Method in Curvilinear Coordinates
Full text linkIn this paper, we introduce and discuss an exactly energy-conserving particle-in-cell method for arbitrary curvilinear coordinates. The flexibility provided by curvilinear coordinates enables the study of plasmas in complex-shaped domains by aligning the grid to the given geometry or by focusing grid resolution on regions of interest without overresolving the surrounding, potentially uninteresting domain. We have achieved this through the introduction of the metric tensor, the Jacobian matrix, and contravariant operators combined with an energy-conserving fully implicit solver. We demonstrate the method’s capabilities using a Python implementation to study several one- and two-dimensional test cases: the electrostatic two-stream instability, the electromagnetic Weibel instability, and the geomagnetic environment modeling reconnection challenge. The test results confirm the capability of our new method to reproduce theoretical expectations (e.g., instability growth rates) and the corresponding results obtained with a Cartesian uniform grid when using curvilinear grids. Simultaneously, we show that the method conserves energy to machine precision in all cases
The state and perceptions of human-crocodile interactions around Murchison Falls conservation area, Uganda
No full textWildlife conflicts between people and large herbivores or mammalian carnivores are widely researched in Africa, but there is limited work on human-crocodile conflicts (HCC). In Uganda, conservation efforts have enabled the recovery of the Nile Crocodile (Crocodylus niloticus) population, yet the expanding human population and activities increasingly overlap with crocodile habitats resulting in negative interactions. This study used a combination of literature review, surveys, and the Nominal Group Technique to investigate the factors underpinning HCC around Murchison Falls Conservation Area. Results indicate that 115 attacks on humans occurred during 2012 2017, 84.3% of these being fatal. Also, 93.1% of the attacks occurred as victims were either fishing or collecting water. Construction of crocodile exclusion enclosures and translocation of problem crocodiles to protected areas were the most preferred mitigation measure. To reduce the prevalence of human injuries and offset local hostility toward crocodiles, conservation actors need to actively engage the affected communities
First characterization of the microbiome of the jointed pumpkin fly, <i>Dacus vertebratus </i>Bezzi (Diptera: Tephritidae)
No full textSeasonal, Latitudinal, and Longitudinal Trends in Nighttime Ozone Vertical Structure on Mars From MAVEN/IUVS Stellar Occultations
Full text linkStellar occultation measurements conducted by the Mars Atmosphere and Volatile and EvolutioN/Imaging UltraViolet Spectrograph instrument were able to make vertically resolved measurements of ozone density in the middle atmosphere of Mars that offered good coverage with respect to latitude, longitude, and local time. These measurements were used to identify systematic variations in the vertical structure of ozone with longitude that could be distinguished from general trends in the evolution of ozone with respect to season and latitude. A total of 583 individual nightside occultations between Martian years 32 and 36 were analyzed, of which 224 were confirmed to have ozone, all found between Ls = 15°–165°. Close to aphelion (Ls = 60°–90°), peak ozone densities between 30 and 40 km altitude were observed to be within error of model predictions at all measured latitudes, but diverged from model predictions before and after this time. At low latitudes, seasonal changes were seen to have the greatest effect on the observed vertical structure of ozone, with detached ozone layer densities at altitudes above 30 km usually varying within approximately a factor of two along a given latitudinal band at a given time of year. Nonetheless, evidence of a persistent regional enhancement of ozone abundance was observed over equatorial latitudes during the aphelion season, spanning a longitude range of approximately 50°–130°E longitude. Planetary waves were clearly observed at higher Southern latitudes during Southern winter, often resulting in order of magnitude variations in ozone density with longitude