Flash size and within-flash time evolution of cloud-top optical emissions: Implications for satellite-based lightning observations

2020 ◽  
Author(s):  
Kenneth Cummins ◽  
Daile Zhang
Keyword(s):  
Time Evolution ◽  
Detection Efficiency ◽  
Local Maximum ◽  
Channel Length ◽  
Main Channel ◽  
Optical Observations ◽  
Light Sources ◽  
Optical Source ◽  
Group Area ◽  
Optical Emissions

<p>This full-year study spanning portions of 2017-18 quantifies GOES-16 Geostationary Lightning Mapper (GLM) flash detection efficiency (DE) in central Florida using the Kennedy Space Center Lightning Mapping Array (LMA). Findings support the expectation that about 70% of all flashes are reported when averaged over all thunderstorms and times-of-day. When quantified as a function of LMA flash parameters, GLM exhibited an average of 40% DE for small (main channel length of 5-8 km), and even lower DE for shorter-length and/or short-duration (less than 200 milliseconds) flashes. Conversely, GLM exhibited more than 95% DE for long-duration flashes with main channel lengths of 50-100 km. DE was somewhat lower during daylight and higher at night.  Flash size and duration, on average are shown to be a critical parameter influencing GLM detection.  Given that this behavior occurred for severe and non-severe storms, it is likely an important contributing factor to the low flash detection efficiency for storms with high flash rates (and resulting small/short flashes) associated with severe weather, thereby modulating the effects of optical scattering and absorption within cloud volumes.</p><p>These findings can be explained by the time-evolution of cloud-top optical emissions derived from observations using the Lightning Imaging Sensor (LIS) onboard the Tropical Rainfall Measuring Mission (TRMM) Satellite. Specifically, LIS group area, energy density, and cloud-top energy in intra-cloud flashes, on average, reached a local maximum value in the very first few milliseconds of a flash and fell to their minimum values at around 10-20 milliseconds into the flash. After that, all parameters gradually increased over the next 80-100 milliseconds to reach the initial values, and then continued to increase for longer-duration flashes. In addition, statistical simulations based on long-term LIS group area observations indicate that about half of the above-threshold light sources are smaller than a LIS pixel (~ 4 km x 4 km) and are the smallest during initial breakdown in IC flashes.</p><p>These observations have implications for expectations about the performance of all satellite lightning observing instruments that are based on optical observations operating in the near-IR portion of the optical spectrum.  The specific values for optical source size and cloud-top energy provided by this study, as a function of time-in-flash, should help refine the expectations for the performance of the upcoming Lightning Imager on the Meteosat Third Generation geostationary satellite.</p><p> </p>

scholarly journals Theoretical evaluation of concentration time and storage coefficient with their application to major dam basins in Korea

2018 ◽  
Vol 19 (2) ◽  
pp. 644-652
Author(s):  
Chulsang Yoo ◽  
Jiho Lee ◽  
Eunsaem Cho
Keyword(s):  
Channel Length ◽  
Main Channel ◽  
Flow Conditions ◽  
Empirical Formulas ◽  
Theoretical Evaluation ◽  
Storage Coefficient ◽  
Concentration Time ◽  
Channel Slope ◽  
And Storage ◽  
Laminar Flow Conditions

Abstract This study theoretically evaluated the basin concentration time and storage coefficient with their empirical formulas available worldwide. The evaluation results were also validated in the application to major dam basins in Korea. The findings are summarized as follows. As a result of analytical analysis, the concentration time was found to be proportional to the main channel length under laminar flow conditions and to the square of it under turbulent flow conditions, but inversely proportional to the channel slope. It was also found that the storage coefficient and the concentration time are linearly but loosely related. Most empirical formulas for the concentration time concurred with the basic equation form, but just a few for the storage coefficient. Applications to major dam basins in Korea also showed that the concentration time agrees well with the result of theoretical analysis. However, the behavior of the storage coefficient varied much, basin by basin, indicating that additional factors may be needed to explain it.

LTCC 3D FLOW FOCALIZATION DEVICE FOR LIQUID-LIQUID PARTIAL SOLVENT EXTRACTION

2016 ◽  
Vol 2016 (CICMT) ◽  
pp. 000111-000117
Author(s):  
Houari Cobas Gomez ◽  
Jéssica Gonçalves da Silva ◽  
Jocasta Mileski Machado ◽  
Bianca Oliveira Agio ◽  
Francisco Jorge Soares de Oliveira ◽  
...  
Keyword(s):  
Solvent Extraction ◽  
Aqueous Phase ◽  
Microfluidic Device ◽  
Flow Rate ◽  
Extraction Efficiency ◽  
Channel Length ◽  
Main Channel ◽  
Process Variables ◽  
3D Flow ◽  
Acetone Concentration

Abstract The present work shows a ceramics microfluidic device for partial solvent extraction scheme. The technology used for device fabrication was Low Temperature Cofired Ceramics (LTCC) which allows us for complex and chemical resistant 3D microfluidic devices. The proposed system aims to partially extract the solvent present in a mixture containing aqueous and organic phases. This scheme uses a 3D flow focalization in order to improve the solvent diffusion into the external aqueous phase. The device is composed by three different parts, the input channels distribution, the main channel and the output channels distribution. The designed input channels distribution ensures a centered 3D focalized solvent stream along the main channel. The focalized solvent mixes with the surrounding water thanks to diffusion. Projected output channels take the central fluid out separately from the surrounding. Thus the device has two different outputs, one for the focalized fluid and another one for the waste fluid, which is the aqueous phase plus solvent. For a device concept proof, acetone and water were used as organic and aqueous phases, respectively. COMSOL Multiphysics was used for device microfluidics and chemical transport simulation. The extraction efficiency was the variable used as indicator for device performance validation. The flow rate ratio between phases, total flow rate, main channel length and focalized stream channel output hydraulic diameter (ODH) were used as process variables for simulation purposes. A factorial experimental planning was used in order to analyze the extraction efficiency taking into account process variables effects. From simulation results it was determined main channel length and ODH as the variables with stronger effect on extraction efficiency. Obtained simulated efficiencies were as high as 80.6%. Considering previous results observations a microfluidic device was fabricated with a main channel length of 21,4 mm and ODH of 214,63 μm. Gas chromatography was used to measured acetone concentration in outputs samples and from here the extraction efficiency. Experimental results were in agreement with simulation, returning extraction efficiencies in the order of 80.8% ± 2.2%.

scholarly journals Multi-Channel Optoelectronic Measurement System for Soil Nutrients Analysis

Electronics ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 451 ◽  
Author(s):  
Liuzheng Ma ◽  
Zhenfeng Li ◽  
Zephania Birech ◽  
Shixin Li ◽  
Yatao Yang ◽  
...  
Keyword(s):  
Measurement System ◽  
Detection Efficiency ◽  
Liquid Crystal Display ◽  
Soil Samples ◽  
Experimental Results ◽  
Circuit Board ◽  
Light Sources ◽  
Relative Standard ◽  
Compensation Concentration ◽  
Optoelectronic Measurement

To solve the problems that occur when farmers overuse chemical fertilizers, it is necessary to develop rapid and efficient portable measurement systems for the detection and quantification of nitrogen (N), phosphorus (P), and potassium (K) in soil. Challenges arise from the use of currently available portable instruments which only have a few channels, namely measurement and the reference channels. We report on a home-built, multichannel, optoelectronic measurement system with automatically switching light sources for the detection of N, P, K content in soil samples. This optoelectronic measurement system consists of joint LED light sources with peak emission wavelengths of 405 nm, 660 nm, and 515 nm, a photodiode array, a circuit board with a microcontroller unit (MCU), and a liquid-crystal display (LCD) touch screen. The straightforward principle for rapid detection of the extractable nutrients (N, P, K) was well-established, and characterization of the designed measurement system was done. Using this multi-channel measurement system, available nutrients extracted from six soil samples could be measured simultaneously. The absorbance compensation, concentration calibration, and nutrition measurements were performed automatically to achieve high consistency across six channels. The experimental results showed that the cumulative relative standard deviations of 1.22%, 1.27%, and 1.00% were obtained from six channels with known concentrations of standard solutions, respectively. The coefficients of correlation for the detection of extracted nutrients of N, P, K content in soil samples using both the proposed method and conventional lab-based method were 0.9010, 0.9471, and 0.8923, respectively. Experimental results show that this optoelectronic measurement system can perform the measurement of N, P, K contents of six soil samples simultaneously and may be used as an actual tool in determining nutrients in soil samples with an improvement in detection efficiency.

On the main channel length-area relationship for channel networks

1987 ◽  
Vol 23 (11) ◽  
pp. 2119-2122 ◽  
Author(s):  
Oscar J. Mesa ◽  
Vijay K. Gupta
Keyword(s):  
Channel Length ◽  
Main Channel ◽  
Channel Networks

scholarly journals The Potentially Dangerous Asteroid (101955) Bennu

2014 ◽  
Vol 2014 ◽  
pp. 1-13
Author(s):  
I. Włodarczyk
Keyword(s):  
Time Evolution ◽  
Software Package ◽  
Optical Observations ◽  
Orbital Elements ◽  
Radar Observations ◽  
The Earth ◽  
The Future ◽  
The Mean ◽  
Orbital Resonances ◽  
Selection Of

We computed impact solutions of the potentially dangerous asteroid (101955) Bennu based on 569 optical observations from September 11.40624 UTC, 1999 to January 20.11189 UTC, 2013, and 29 radar observations from September 21, 1999, through September 29, 2011. Using the freely available OrbFit software package, we can follow its orbit forward in the future searching for close approaches with the earth, which can lead to possible impacts up to 2200. With the A2 nongravitational parameter in the motion of the asteroid (101955) Bennu we computed possible impact solutions using different JPL planetary and lunar ephemerides and different number of additional massive perturbed asteroids. The possible impact path of risk for 2175 is presented. Additionally, we computed possible impact solutions using the normal places method of the selection of Bennu’s astrometric observations. Moreover, we computed time evolution of the mean orbital elements and the orbital nodes of Bennu 5 kyr in the backwards and 1 kyr in the future using the Yarkovsky effects. We computed the mean motion and secular orbital resonances of the Bennu. We also computed the influence of the JPL planetary and lunar ephemerides DE403, DE405, DE406, DE414, and DE423 on the close approaches of the asteroid (101955) Bennu with the earth.

scholarly journals Learning a Convolutional Autoencoder for Nighttime Image Dehazing

Information ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 424
Author(s):  
Mengyao Feng ◽  
Teng Yu ◽  
Mingtao Jing ◽  
Guowei Yang
Keyword(s):  
State Of The Art ◽  
Signal To Noise Ratio ◽  
Local Maximum ◽  
Structural Similarity ◽  
Light Sources ◽  
Ambient Illumination ◽  
Image Dehazing ◽  
Edge Preserving ◽  
Convolutional Autoencoder ◽  
Maximum Method

Currently, haze removal of images captured at night for foggy scenes rely on the traditional, prior-based methods, but these methods are frequently ineffective at dealing with night hazy images. In addition, the light sources at night are complicated and there is a problem of inconsistent brightness. This makes the estimation of the transmission map complicated in the night scene. Based on the above analysis, we propose an autoencoder method to solve the problem of overestimation or underestimation of transmission captured by the traditional, prior-based methods. For nighttime hazy images, we first remove the color effect of the haze image with an edge-preserving maximum reflectance prior (MRP) method. Then, the hazy image without color influence is input into the self-encoder network with skip connections to obtain the transmission map. Moreover, instead of using the local maximum method, we estimate the ambient illumination through a guiding image filtering. In order to highlight the effectiveness of our experiments, a large number of comparison experiments were conducted between our method and the state-of-the-art methods. The results show that our method can effectively suppress the halo effect and reduce the effectiveness of glow. In the experimental part, we calculate that the average Peak Signal to Noise Ratio (PSNR) is 21.0968 and the average Structural Similarity (SSIM) is 0.6802.

scholarly journals Variations of the 630.0 nm airglow emission with meridional neutral wind and neutral temperature around midnight

2018 ◽  
Author(s):  
Chih-Yu Chiang ◽  
Sunny Wing-Yee Tam ◽  
Tzu-Fang Chang
Keyword(s):  
Emission Rate ◽  
Local Maximum ◽  
Optical Observations ◽  
Neutral Wind ◽  
Emission Rates ◽  
Emission Layer ◽  
Neutral Winds ◽  
Neutral Temperature ◽  
Different Temperatures ◽  
Volume Emission

Abstract. Enhancements in 630.0 nm airglow around midnight at equatorial latitudes were observed by many optical observations. Such features had been suggested as the signature of thermospheric midnight temperature maximum (MTM) effect, which was associated with temperature and meridional neutral winds. This study investigates the influence of neutral temperature and meridional neutral wind on the volume emission rates of the 630.0 nm nightglow. We utilize the SAMI2 model to simulate the charged and neutral species at the 630.0 nm nightglow emission layer under different temperatures with and without the effect of neutral wind. The results show that the neutral wind is more efficient than temperature variation in affecting the nightglow emission rates. However, the emission rate features a local maximum in its variation with the temperature. Two kinds of tendencies can be seen regarding the temperature that corresponds to the turning point, which is named the turning temperature (Tt) in this study: firstly, Tt decreases with the emission rate for the same altitude; secondly, for approximately the same emission rate, Tt increases with the altitude.

scholarly journals An optical study of multiple NEIAL events driven by low energy electron precipitation

2008 ◽  
Vol 26 (8) ◽  
pp. 2435-2447 ◽  
Author(s):  
J. M. Sullivan ◽  
M. Lockwood ◽  
B. S. Lanchester ◽  
E. P. Kontar ◽  
N. Ivchenko ◽  
...  
Keyword(s):  
Langmuir Wave ◽  
Low Energy ◽  
Optical Observations ◽  
Optical Data ◽  
Small Scale ◽  
Ion Acoustic Wave ◽  
Optical Emissions ◽  
Multiple Wavelength ◽  
Ion Acoustic ◽  
Low Energy Electrons

Abstract. Optical data are compared with EISCAT radar observations of multiple Naturally Enhanced Ion-Acoustic Line (NEIAL) events in the dayside cusp. This study uses narrow field of view cameras to observe small-scale, short-lived auroral features. Using multiple-wavelength optical observations, a direct link between NEIAL occurrences and low energy (about 100 eV) optical emissions is shown. This is consistent with the Langmuir wave decay interpretation of NEIALs being driven by streams of low-energy electrons. Modelling work connected with this study shows that, for the measured ionospheric conditions and precipitation characteristics, growth of unstable Langmuir (electron plasma) waves can occur, which decay into ion-acoustic wave modes. The link with low energy optical emissions shown here, will enable future studies of the shape, extent, lifetime, grouping and motions of NEIALs.

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